belajar: Flowchart bagian I

Flowchart Techniques

Programmers use different kinds of tools or aids which help them

in developing programs faster and better. Such aids are studied

in the following paragraphs. Important aids available to a programmer

are flowcharting and decision tables which help him in

constructing programs very fast and very easily.

1.1.1 Flowcharts

A flowchart is a graphical representation of the sequence of operations

in an information system or program. Program flowcharts

show the sequence of instructions in a single program or

subroutine.

Flowchart uses boxes of different shapes to denote different

types of instructions. The actual instructions are written within

these boxes using clear and concise statements. These boxes are

connected by solid lines having arrow marks to indicate the flow

of operation, that is, the exact sequence in which the instructions

are to be executed. Since a flowchart shows the flow of operations

in pictorial form, any error in the logic of the procedure can be

detected easily. Once the flowchart is ready, the programmer can

forget about the logic and can concentrate only on coding the

operations in each box of the flowchart in terms of the statements

of the programming language. This will normally ensure an

error-free program.

A flowchart is basically the plan to be followed when the program

is written. It acts like a road map for a programmer and I

2 Flowcharting Concepts and Algorithms

guides him in proceeding from the starting point to the final

point while writing a computer program.

For a beginner it is strongly recommended that a flowchart

be drawn first in order to reduce the number of errors and omissions

in the program. Moreover, it is a good practice to have a

flowchart along with a computer program as it is very helpful

during the testing of the program and also in incorporating any

modifications in the program.

1.1.2 Flowchart Symbols

Only a few symbols are needed to indicate the necessary operations

in a flowchart. These symbols have been standardized by

the American National Standards Institute (ANSI). These

symbols are shown in Figure 3.1 and their functions are discussed

below.

Terminal

The terminal symbol, as the name implies, is used to indicate the

starting (BEGIN), stopping (END), and pause (HALT) in the program

logic flow. It is the first symbol and the last symbol in the

program logic. In addition, if the program logic calls for a pause

in the program, that also is indicated with a terminal symbol. A

pause is normally used in the program logic under some error

conditions or in case the forms had to be changed in the computer’s

line printer during the processing of that program.

Input/Output

The input/output symbol is used to denote any function of an

input/output device in the program. If there is a program

instruction to input data from a disk, tape, card reader, terminal,

or any other type of input device, that step will be indicated in

the flowchart with an input/output symbol. Similarly, all output

instructions, whether it is output on a printer, magnetic tape,

magnetic disk, terminal screen, or any output device, are indicated

in the flowchart with an input/output symbol.

Processing

A processing symbol is used in a flowchart to represent arithmetic

and data movement instructions. Thus, all arithmetic

Flowchart Techniques 3

Figure 1.1 Flowchart symbols

SYMBOL EXAMPLE

TERMINAL

BEGIN

END

INPUT/

OUTPUT

INPUT

X,Y

PROCESSING

ENTRY CONNECTOR

YES

CONDITION

DECISION DIAMOND

CONNECTOR

(TRANSFER)

X,Y

(X+Y)

START ACTION HERE.

STOP ACTION HERE.

TAKE TWO VALUES FROM

AN EXTERNAL SOURCE AND

ASSIGN THEM TO X & Y ON

A TERMINAL/SCREEN

WRITE THE VALUES

CONTAINED IN X & Y ON

A TERMINAL/SCREEN

ADD THE VALUE CONTAINED

IN Y TO THE VALUE

CONTAINED IN X AND

PLACE THE RESULT IN Z

AN ENTRY IN THE FLOW CHART

IS MADE AT THE CONNECTING

POINT MARKED 1

IF CONDITION IS SATISFIED

THEN YES PATH IS TO BE

FOLLOWED OTHERWISE NO

ROUTE IS TO BE TAKEN.

THE ARROWS INDICATE THE

ROUTES FOR SYSTEMATIC

SOLUTION OF THE PROBLEM.

A TRANSFER OF PROBLEM

SOLUTION IS MADE AT THE

CONNECTOR POINT

IN THE FLOW CHART.

FLOW LINES

4 Flowcharting Concepts and Algorithms

processes such as adding, subtracting, multiplying and dividing

are shown by a processing symbol. The logical process of moving

data from one location of the main memory to another is also

denoted by this symbol. When more than one arithmetic and data

movement instructions are to be executed consecutively, they are

normally placed in the same processing box and they are

assumed to be executed in the order of their appearance.

Flow lines

Flowlines with arrowheads are used to indicate the flow of operation,

that is, the exact sequence in which the instructions are to

be executed. The normal flow of flowchart is from top to bottom

and left to right. Arrowheads are required only when the normal

top to bottom flow is not to be followed. However, as a good practice

and in order to avoid confusion, flow lines are usually drawn

with an arrowhead at the point of entry to a symbol. Good

practice also dictates that flow lines should not cross each other

and that such intersections should be avoided whenever possible.

Decision

The decision symbol is used in a flowchart to indicate a point at

which a decision has to be made and a branch to one of two or

more alternative points is possible. Figure 1.2 shows three different

ways in which a decision symbol can be used. It may be noted

from these examples that the criterion for making the decision

should be indicated clearly within the decision box. Moreover, the

condition upon which each of the possible exit paths will be

executed, should be identified and all the possible paths should

be accounted for. During execution, the appropriate path is followed

depending upon the result of the decision.

Connector

If a flowchart becomes very long, the flow lines start crisscrossing

at many places that causes confusion and reduces the clarity of

the flowchart. Moreover, there are instances when a flowchart

becomes too long to fit in a single page and the use of flow lines

becomes impossible. Thus, whenever a flowchart becomes too

complex that the number and direction of flow lines is confusing

or it spreads over more than one page, it is useful to utilize the

Flowchart Techniques 5

Figure 1.2 Different decision symbols with different ways of branching

I = 10

Yes

(a) Two-way branch

Other

I = ?

A < B

(b) Three-way branch

A = B

A & B

COMPARE A > B

1 2 3 4 5

6 Flowcharting Concepts and Algorithms

connector symbol as a substitute for flow lines. This symbol represents

an entry from, or an exit to another part of the flowchart.

A connector symbol is represented by a circle and a letter or

digit is placed within the circle to indicate the link. A pair of

identically labeled connector symbols are commonly used to indicate

a continued flow when the use of a line is confusing. So two

connectors with identical labels serve the same function as a long

flow line. That is, they show an exit to some other chart section,

or they indicate an entry from another part of the chart. How is it

possible to determine if a connector is used as an entry or an exit

point? It is very simple: if an arrow enters but does not leave a

connector, it is an exit point and program control is transferred to

the identically labeled connector that does have an outlet. It may

be noted that connectors do not represent any operation and their

use in a flowchart is only for the sake of convenience and clarity.

Example 1.1

Draw a flowchart for adding marks in ten subjects obtained by a

student in an examination. The output should print the percentage

of marks of the student in the examination.

The flowchart for this problem is given in Figure 1.3

The first symbol is a terminal labeled START. It shows that this

is the starting point or beginning of our flowchart logic. The second

symbol is an input/output (I/O) symbol that is labeled specifically

to show that this step is to read input data. This step will

input the roll number, name, and the marks obtained by the

student from an input device into the main storage of the computer

system. The third symbol is a processing symbol which is

suitably labeled to indicate that at this step, the computer will

add the marks obtained by the student in various subjects and

then store the sum in a memory location which has been given

the name TOTAL. The fourth symbol is again a processing symbol.

The label inside it clearly indicates that the percentage

marks obtained by a student is calculated at this stage by

dividing TOTAL by 10 and the result is stored in a memory location

which has been given the name PERCENTAGE. The fifth

symbol is an input/output (I/O) symbol and is labeled WRITE

OUTPUT DATA.

Flowchart Techniques 7

Figure 1.3 Flowchart for calculating percentage of marks

Example 1.2

Draw a flowchart for calculating the average percentage marks of

50 students. Each student appeared in ten subjects. The flowchart

should show the counting of the number of student who

have appeared in the examination and the calculation should

stop when the number of counts reaches the number 50.

Since all the students have appeared in the same examination,

so the process of calculation and printing the percentage

marks obtained by each student will basically remain the same.

The process of reading the input data, adding the marks of all

START

READ

PERCENTAGE

INPUT

DATA

ADD-MARKS OF

ALL SUBJECTS

GIVING TOTAL

= TOTAL/10

DATA

OUTPUT

WRITE

STOP

8 Flowcharting Concepts and Algorithms

Figure 1.4 Flowchart for example 1.2

START

READ

PERCENTAGE

INPUT

DATA

ADD-MARKS OF

ALL SUBJECTS

GIVING TOTAL

= TOTAL/10

DATA

OUTPUT

WRITE

STOP

COUNT = 0

ADD 1 TO COUNT

COUNT = 50

Yes

Flowchart Techniques 9

subjects, calculating the percentage, and then writing the output

data, is to be repeated for all the 50 students. In this situation

where the same logical steps can be repeated, the flow line symbols

are used in a flowchart to indicate the repetitive nature of

the logic in the form of a loop.

Figure 1.4 shows a flowchart which uses a decision step to

terminate the algorithm. In this flowchart, another variable

COUNT has been introduced which is initialized to zero outside

the process loop and is incremented by 1 after processing the data

for each student. Thus, the value of COUNT will always be equal

to the number of students whose data has already been processed.

At the decision step, the value of COUNT is compared

with 50 which is the total number of students who have appeared

for the examination. The steps within the process loop are

repeated until the value of COUNT becomes equal to 50. As soon

as the value of COUNT becomes equal to 50, the instruction at

the decision step causes the control to flow out of the loop and the

processing stops because a terminal symbol labeled STOP is

encountered.

Designing a General Flowchart

The flowchart shown in Figure 1.4 is not a general flowchart for

the Example 1.2 for calculating the percentage of marks of any

number of students appearing in the examination. A good program

should be general in nature. For example, in this case we

should write a program that need not be modified every time,

even if the total number of students changes.

To overcome these drawbacks, another method can be

adopted to control the loop. In this method, the end of input data

is marked by a trailer record, that is, the last data record in the

input is followed by a record whose main purpose is to indicate

that the end of the input data has been reached. Suppose the first

7 characters of the input record of a student represents his roll

number (ROLLNO). Since 0000000 is never used as a roll number,

a value of 0000000 as the first 7 characters can be used to

represent the trailer record. As each input record is processed,

the ROLLNO can be compared with 0000000 to determine if processing

is complete. The logic of this process is illustrated in the

flowchart given in Figure 1.5.

10 Flowcharting Concepts and Algorithms

Figure 1.5 General flowchart for example 1.2

What is Trailer Record?

The concept of a trailer record centers around the notion of

selecting a field (a particular item of data) in the input record

which will be used to indicate the end of data, and then selecting

a trailer value also known as sentinel value which will never

occur as normal data value for that field. The roll number

0000000 is a trailer record for Example 1.2.

START

READ

PERCENTAGE

INPUT

DATA

ADD-MARKS OF

ALL SUBJECTS

GIVING TOTAL

= TOTAL/10

DATA

OUTPUT

WRITE

STOP

ROLL NO=0000000

Yes

Flowchart Techniques 11

Example 1.3

Extend the flowchart represented in Figure 1.5 to count the

number of students who have scored percentage marks more

than 30. The flowchart should give the result of the students

scoring the percentage marks equal to or more than 30.

Figure 1.6 Flowchart for example 1.3

START

READ

PERCENTAGE

INPUT

DATA

ADD-MARKS OF

ALL SUBJECTS

GIVING TOTAL

= TOTAL/10

DATA

OUTPUT

WRITE

COUNT = 0

ADD 1 TO COUNT

ROLL NO.9999999

PERCENTAGE

Yes

STOP

WRITE

COUNT

= > 30

Yes

12 Flowcharting Concepts and Algorithms

The flowchart in Figure 1.6 is a solution to this problem.

There are two decision symbols in this flowchart. The first decision

symbol checks for a trailer record by comparing ROLLNO

against the value 9999999 to determine if processing is complete.

The second decision symbol is used to check whether the student

has passed or failed by comparing the percentage marks obtained

by him against 30. If the student’s PERCENTAGE is equal to or

more than 30, then he has passed, otherwise he has failed. Note

from the flowchart that the operation WRITE OUTPUT DATA is

performed only if the student has passed. If he has failed, we

directly perform the operation READ INPUT DATA without performing

the WRITE operation. This ensures that the output list

provided by the computer will contain the details of only those

students who have passed in the examination.

Another point to be noted in this flowchart is the use of variable

COUNT. This variable has been initialized to zero in the

beginning and is increased by 1 every time the operation WRITE

OUTPUT DATA is performed. But we have seen that the operation

WRITE OUTPUT DATA is performed only for the students

who have passed. Hence, the variable COUNT will be increased

by 1 only in the case of those students who have passed. Thus,

the value of COUNT will always be equal to the number of students

whose data has already been processed and who have been

identified as passed. Finally, when the trailer record is detected,

the operation WRITE COUNT will print out the final value of

COUNT that will be equal to the total number of students who

have passed the examination.

1.1.3 Flowcharting Rules

(a) First formulate the main line of logic, then incorporate the

details.

(b) Maintain a consistent level of detail for a given flowchart.

interested in greater details can refer to the program itself.

(d) Words in the flowchart symbols should be common statements

and easy to understand.

(e) Be consistent in using names and variables in the flowchart.

(f) Go from left to right and top to bottom in constructing the

flowchart.

Flowchart Techniques 13

(g) Keep the flowchart as simple as possible. The crossing of

flow lines should be avoided as far as possible.

(h) If a new flowcharting page is needed, it is recommended

that the flowchart be broken at an input or output point.

Moreover, properly labeled connectors should be used to link

the portions of the flowchart on different pages.

1.1.4 Advantages of Flowcharts

Conveys Better Meaning

Since a flowchart is a pictorial representation of a program, it is

easier for a programmer to understand and explain the logic of

the program to some other programmer.

Analyses the Problem Effectively

A macro flowchart that charts the main line of logic of a software

system becomes a system model that can be broken down into

detailed parts for study and further analysis of the system.

Effective Joining of a Part of a System

A group of programmers are normally associated with the design

of large software systems. Each programmer is responsible for

designing only a part of the entire system. So initially, if each

programmer draws a flowchart for his part of design, the flowcharts

of all the programmers can be placed together to visualize

the overall system design. Any problem in linking the various

parts of the system can be easily detected at this stage and the

design can be accordingly modified. Flowcharts can thus be used

as working models in the design of new programs and software

systems.

Efficient Coding

Once a flowchart is ready, programmers find it very easy to write

the concerned program because the flowchart acts as a roadmap

for them. It guides them in proceeding from the starting point of

the program to the final point ensuring that no steps are omitted.

The ultimate result is an error free program developed at a

faster rate.

14 Flowcharting Concepts and Algorithms

Systematic Debugging

Even after taking full care in program design, some errors may

remain in the program because the designer might have never

thought about a particular case. These errors are detected only

when we start executing the program on a computer. Such type of

program errors are called bugs and the process of removing these

errors is known as debugging. A flowchart is very helpful in

detecting, locating, and removing mistakes (bugs) in a program

in a systematic manner.

Systematic Testing

Testing is the process of confirming whether a program will successfully

do all the jobs for which it has been designed under the

specified constraints. For testing a program, different sets of data

are fed as input to that program to test the different paths in the

program logic.

1.1.5 Limitations of Flowcharts

Takes More Time to Draw

Flowcharts are very time consuming and laborious to draw with

proper symbols and spacing, especially for large complex programs.

Difficult to Make Changes

Owing to the symbol-string nature of flowcharting, any changes

or modifications in the program logic will usually require a completely

new flowchart. Redrawing a flowchart is tedious and

many companies either do not change them or produce the

flowchart by using a computer program to draw it.

Non-standardization

There are no standards determining the amount of detail that

should be included in a flowchart.

1.1.6 Levels of Flowcharts

A flowchart that outlines the main segments of a program and

shows lesser detail is a macro-flowchart. On the other hand, a

Flowchart Techniques 15

Figure 1.7 Details of the processing block of Figure 1.3 for adding marks in 10

subjects

flowchart with more detail is a micro-flowchart. For example, let

us consider the examination problem that we have already discussed

in Examples 1.3 and 1.4. In all the flowcharts of the

examination problem, there is a processing box having the

instruction "ADD MARKS OF ALL SUBJECTS GIVING

TOTAL". In order to display how the values of TOTAL is calculated,

a detailed flowchart can be drawn as shown in Figure 1.7.

In a similar manner, the input/output (I/O) boxes for the READ

and WRITE operations can also be converted to a detailed flowchart.

ADD-MARKS OF

ALL SUBJECTS

GIVING TOTAL

A MICRO

FLOW CHART

I = 1

TOTAL = 0

TOTAL = TOTAL + MARKS (I)

I = I + 1

I > 10

YES

PART OF A MACRO

FLOW CHART

16 Flowcharting Concepts and Algorithms

1.2 Pseudocode or Metacode or PDL

Pseudocode is another program analysis tool that is used for

planning program logic. "Pseudo" means imitation or false and

"Code" refers to the instructions written in a programming language.

Pseudocode, therefore, is an imitation of actual computer

instructions. These pseudo instructions are phrases written in

ordinary natural language (e.g., English, French, German, etc.).

Instead of using symbols to describe the logic steps of a program,

as in flowcharting, pseudocode uses a structure that resembles

computer instructions. Because it emphasises the design of the

program, pseudocode is also called Program Design Language

(PDL).

Pseudocode is made up of the following basic logic structures

that have been proved to be sufficient for writing any computer

program :

1. Sequence

2. Selection (IF...THEN...ELSE

or IF....THEN)

1. Iteration (DO...WHILE or REPEAT...UNTIL)

1.2.1 Sequence

Sequence logic is used for performing instructions one after

another in sequence. Thus, for sequence logic, pseudocode

instructions are written in the order, or sequence, in which they

are to be performed. The logic flow of pseudocode is from the top

to the bottom. Figure 1.8 shows an example of sequence logic

structure.

1.2.2 Selection

Selection logic, also known as decision logic, is used for making

decisions. It is used for selecting the proper path out of the two or

more alternative paths in the program logic. Selection logic is

depicted as either an IF...THEN...ELSE or IF.....THEN structure.

The flowcharts shown in Figures 1.9 and 1.10 illustrate the logic

of these structures. Their corresponding pseudocode is also given

in these figures.

Flowchart Techniques 17

The IF...THEN...ELSE construct says that if the condition is

true, then do process 1, else (if the condition is not true) do process

2. Thus, in this case either process 1 or process 2 will be

executed depending on whether the specified condition is true or

false. However, if we do not want to choose between two processes

and we simply want to decide if a process is to be performed

or not, then the IF...THEN structure is used.

Figure 1.8 Pseudocode for sequence structure

FLOWCHART

PROCESS 1

PROCESS 2

PSEUDOCODE

Process 1

Process 2

18 Flowcharting Concepts and Algorithms

The IF...THEN structure says that if the condition is true,

then do process 1; and if it is not true, then skip over process 1. In

both the structures, process 1 and process 2 can actually be one

or more processes. They are not limited to a single process. END

IF is used to indicate the end of the decision structures.

Figure 1.9 Pseudocode for If-Then-Else structure

FLOWCHART

PROCESS 2 PROCESS 1

PSEUDOCODE

If Condition

END IF

ROLL NO.9999999

THEN process 1

ELSE

process 2

YES

Flowchart Techniques 19

Figure 1.10 Pseudocode for If-Then selection structure

1.2.3 Iteration Logic

Iteration logic is used when one or more instructions may be

executed several times depending on some condition. It uses two

structures called the DO...WHILE and the REPEAT...UNTIL.

They are illustrated by flowcharts in Figure 1.11 and Figure 1.12

respectively. Their corresponding pseudocodes are also given in

these figures. Both DO...WHILE and REPEAT...UNTIL are used

for looping.

FLOWCHART

PROCESS 1

PSEUDOCODE

IF CONDITION

END IF

CONDITION

THEN PROCESS1

YES

20 Flowcharting Concepts and Algorithms

1.2.4 Differences between Do..While and Repeat.. Until

loops

The differences between the two loops are that in the

Figure 1.11 Pseudo-code for Do.. While structure

FLOWCHART

PROCESS 1

PSEUDOCODE

DO WHILE CONDITION

ENDDO

CONDITION

PROCESS 1

PROCESS n

YES

PROCESS n

Flowchart Techniques 21

Figure 1.12 Pseudo-code for Repeat..Until structure

DO...WHILE, the looping will continue as long as the condition is

true. The looping stops when the condition is not true. On the

other hand, in case of REPEAT...UNTIL, the looping continues

FLOWCHART

PROCESS n

PROCESS 1

PSEUDOCODE

REPEAT

UNTIL CONDITION

CONDITION

PROCESS 1

PROCESS 2

YES

22 Flowcharting Concepts and Algorithms

until the condition becomes true. That is, the execution of the

statements within the loop is repeated as long as the condition is

not true. In both the DO...WHILE and REPEAT...UNTIL, the

loop must contain a statement that will change the condition that

controls the loop. Also the condition is tested at the top of the loop

in the DO...WHILE loop structure and at the bottom of the loop

in the REPEAT...UNTIL structure. The "ENDDO" marks the end

of a DO...WHILE structure and UNTIL followed by some condition

marks the end of the REPEAT...UNTIL structure.

Example 1.4

The following pseudocode describes the policy of a company to

award the bonus to an employee.

Input

Employee number, pay, position code & years.

position code = 1

THEN

set bonus to 1 week’s pay

ELSE

IF position code = 2

THEN

IF 2 weeks pay > 700

THEN

set bonus to 700

ELSE

set bonus to 2 week’s pay

END IF

ELSE

set Bonus to 1.5 week’s pay

END IF

END IF

IF year greater then 10

THEN

Add 100 to bonus

ELSE

IF years less than 2

THEN

cut bonus to half

Flowchart Techniques 23

ELSE

bonus stays the same

END IF

Print employee number & bonus

Example 1.5

This example illustrates the policy of a bank or a financial institution

for giving a loan to an individual.

Input mortgage amount

IF amount < 25,000

THEN

down payment = 3% of amount

ELSE

payment1 = 3% of 25,000

payment2 = 5% of (amount - 25,000)

down payment = payment1 + payment2

END IF

print down payment

Example 1.6

The following program in pseudocode form illustrates the policy

of a company to give the commission to a sales person.

Input sales

IF sales < 500

THEN

Commission = 2% of sales.

ELSE

IF sales < 5000

THEN

Commission = 5% of sales

ELSE

Commission = 10% of sales

END IF

Print Commission

1.2.5 Advantages of Pseudocodes

Pseudocode has three main advantages:

24 Flowcharting Concepts and Algorithms

(a) Converting a pseudocode to a programming language is

much more easier as compared to converting a flowchart or a

decision table.

(b) As compared to a flowchart, it is easier to modify the pseudocode

of a program logic when program modifications are

necessary.

than drawing an equivalent flowchart. Pseudocode is easier

to write than an actual programming language because it

has only a few rules to follow, allowing the programmer to

concentrate on the logic of the program.

1.2.6 Limitations of Pseudocodes

(a) In case of pseudocode, a graphic representation of program

logic is not available.

(b) There are no standard rules to follow in using pseudocode.

Different programmers use their own style of writing pseudocode

and hence communication problems occur due to lack

of standardization.

the pseudocode, as compared to flowcharting.

1.2.6 Limitations of Pseudocodes

(a) In case of pseudocode, a graphic representation of program

logic is not available.

(b) There are no standard rules to follow in using pseudocode.

Different programmers use their own style of writing pseudocode

and hence communication problems occur due to lack

of standardization.

the pseudocode, as compared to flowcharting.

1.3 Programming Techniques

You can solve different types of business or scientific problems on

a computer. All you have to do is to analyse the problem, write a

step by step solution and translate it into a language understandable

by a computer.

Flowchart Techniques 25

1.3.1 Problem Definition

Let us take an example of a problem faced in day- to- day life.

Suppose you want to reach your school computer laboratory at 8

AM. You would lay out a plan to get ready by 7 AM, then take a

bus/rikshaw and reach at the gate of your school. Then climb up

the stairs to arrive in the laboratory. For all these movements,

you will note the time taken for each part. If due to some reason,

you are unable to get ready by 7 AM and you already know that

it takes one hour to reach from house to school laboratory by

bus/rikshaw, then you will take a faster means of transportation.

You may take an autorikshaw or a taxi. Thus, a very simple

problem of reaching the computer laboratory of your school by 8

AM will need several steps for solution. Each step is to be accurately

defined/marked so that no guess work is necessary. You

can thus represent the solution of this problem in three steps

shown in Figure 1.11.

In Figure 1.13, steps 1, 2 and 3 appear to be very simple. In

actual practice when you have to give instructions to a student,

who is going for the first time, it may not be so easy. For example,

you have to define the word "READY" precisely so that he knows

exactly what he has to do by 7AM to get READY. Similarly in

step 2, you may have to clearly specify the bus route number, the

bus stop to board the bus, the place to get down from the bus etc.

You may also like to tell that a bus is not to be boarded, if it is

overcrowded. The word "overcrowded" needs to be exactly

defined. Finally, step 3 needs further elaboration about the room

number and floor number; where the computer laboratory is

located and how to reach there.

You can explain all this to a person who does not know any

thing about the computer laboratory, provided you know it correctly.

In the same way, you can solve a problem on a computer,

if you know exactly what it is and how to solve it manually.

We shall solve a few problems using flowchart.

26 Flowcharting Concepts and Algorithms

Figure 1.13 Step by step solution to reach school computer laboratory (LAB)

Example 1.7

Consider the flowchart shown in Figure 1.14. Give the value of

BONUS under the following conditions:

(a) X = 20, Y = 10

(b) X = 10, Y = 20

Solution

(a) The value of X and Y are 20 and 10 respectively. These values

are inputted in step 2. The value of BONUS is taken as

500 in step 1. Since the values of X = 20 and Y = 10, so in

step 4, X is more than Y.

GET READY

BY 7 AM

STEP 1

TAKE A BUS

FOR SCHOOL

STEP 2

STEP 3

REACH

COMPUTER

LAB BY 8 AM

Flowchart Techniques 27

Therefore the Yes route is to be followed. Hence the new

value of BONUS is the old value of BONUS + 100 i.e. 600.

Hence the value of BONUS written in step 5 is 600.

(b) Here, the value of X=10 & Y=20. Therefore in step 4, the

diamond decision shows that X is less than Y. Therefore,

the No route is followed. The value of BONUS remains 500

only. Hence the result is 500.

Figure 1.14 Bonus calculation

Example 1.8

Here are six types of values for the variables A, B, and C.

(a) A=9, B=5, C=1 (b) A=7, B=3, C=9

(e) A=6, B=3, C=8 (f) A=2, B=3, C=6

1. Using each type of data, with the flowchart shown in Figure

1.15, state the output in each case.

BEGIN

INPUT

X,Y

BONUS = 500

X > Y

BONUS BONUS + 100

YES

BONUS

END

STEP 1

STEP 2

STEP 3

STEP 4

STEP 5

STEP 6

28 Flowcharting Concepts and Algorithms

2. What does the procedure do?

1. What happens, if all the values of A, B and C are the same?

Solution

1.(a) The values of A, B and C are accepted as 9, 5 and 1 respectively.

In step 3, the value of A is compared with B. Since 9

is greater than 5, therefore the YES path is followed. Once

again, in step 4, the value of A is compared with C. Here 9

is greater than 1. So the YES path is followed. In step 5,

value of ‘A’ is printed which is 9. Hence the answer is 9.

(b) The values of A, B and C are accepted as 7, 3 and 9 respectively.

In step 3 the value of A is compared with B. Since 7

is greater than 3, therefore, the YES path is followed. In

step 4, the value of A is compared with C. Since 7 is less

than 9, therefore the path corresponding to NO is followed.

Hence the value of C which is 9 will be printed.

As understood from steps (a) and (b) above, we find

that in step 5 the value of B will be printed as 9.

(d) The values of A, B and C are accepted as 4, 8 and 2 respectively.

In step 5, the value of B will be printed as 8.

(e) The values of A, B and C are accepted as 6, 3 and 8 respectively.

The value of C which is 8 will be printed in step 5.

(f) The values of A, B and C are accepted as 2, 3 and 6 respectively.

The value of C which is 6 is printed in step 5.

2. It is evident from the flowchart that the values of A, B and

C are compared with each other and the one that contains

the highest numeral value is printed. If A has the highest

value, then A is printed, otherwise, if B has the highest

value, then B is printed or finally the value of C is printed if

it has the highest value.

1. If A, B and C have equal values, then the value of C which

is the same as that of B or A is printed.

Flowchart Techniques 29

Figure 1.15 Calculation of output for different values of A, B and C

Example 1.9

The flowchart in Figure 1.16 uses connector symbols labelled as

1, 2 and 3. Find the output if the input is:

(a) A=10, B=15,

(b) A=20, B=20,

(d) A=10, B=5.

A > B

A > C

B > C

BEGIN STEP 1

INPUT

A,B,C

NO YES

NO YES NO YES

STEP 2

STEP 3

STEP 4

STEP 5

STEP 6

PRINT C PRINT B PRINT C PRINT A

END END END END

30 Flowcharting Concepts and Algorithms

Solution

(a) In step 2 of Figure 1.16, the values of A and B are taken to

be 10 and 15 respectively. In step 3, the value of A is not

less than 10, so the path corresponding to NO is followed.

In step 4, the value of B is not less than 20, hence a

path corresponding to NO is followed. In step 5, the value of

(A+B) is assigned to C, i.e. C becomes (10+15) or equal to

25. Finally, in step 6, the value of C which is 25 is printed.

(b) In step 2, the values of A and B are taken as 20 and 20

respectively. Steps 3 to 5 are similar to that followed in part

(a) above. The value of C is now equal to (A+B) which is 40.

Hence 40 is printed.

respectively. In step 3, the value of A is less than 10. Hence

the YES path is followed. This is connected to the adjacent

figure via the connector 1. Hence the value of A is now the

old value of A + 3, i.e. 7.

Further, the decision diamond puts the question "Is A less

than 10?" The answer is YES. Hence the control is transferred

to the lower figure via connector 2. The new value

of B becomes the old value of B multiplied by 5 which is 1 x

3 = 1. The diamond compares the value of B with 20. Since

B is less than 20, so the control is transferred back at 2 in

this block. The new value of B becomes the old value of B

multiplied by 3.

= 3 × 3

= 9

This new value of B i.e. 9 is again compared in the decision

diamond. Since 9 is less than 20, the control goes to connecter

2. B is again multiplied and the current value of B is

3 × 9 = 27. As 27 is not less than 20, so the NO path is

followed.

The value of C = current value of B + 3

= 27 + 3

= 30

The value 30 of C is now transferred to step 6 i.e. PRINT C.

Hence the value 30 is printed.

Flowchart Techniques 31

Figure 1.16 Flowchart for example 1.9

(d) Here A=10 and B=5

In step 3, the value of A is not less than 10, so the NO path

is followed.

A (A+3)

A < 10

C = 3 * A

Yes

B * 3

B < 20

2 B

Yes

(B + 3)

STEP 1

STEP 2

STEP 3

STEP 4

STEP 5

STEP 6

STEP 7

BEGIN

INPUT

A,B

A < 10

B < 20

C (A + B)

PRINT C

END

Yes

32 Flowcharting Concepts and Algorithms

In step 4, the value of B is 5 which is less than 20.

Hence connector 2 takes the control to right hand lower

side flowchart. The current value of B becomes the old

value of B multiplied by 3 which is now 15. This value of B

i.e. 15 is the current value of B. In the decision diamond,

this value of B is compared with 20. Since 15 is less than

20, so the YES path is followed. The control is transferred

back via connector 2. The new value of B is calculated

which will be 15 × 3 i.e. 45. This current value of B is again

compared with 20. As it is not less than 20, so the NO path

is followed.

The value of C = current value of B + 3

= 45 + 3

= 48

Control is transferred to step 6 via connector 3 and the value of C

is printed. Thus the value of C = 48.

1.3.2 Loop

Many jobs that are required to be done with the help of a computer

are repetitive in nature. For example, calculation of salary

of different workers in a factory is given by the (No. of hours

worked)× (wage rate). This calculation will be performed by an

accountant for each worker every month. Such types of repetitive

calculations can easily be done using a program that has a loop

built into the solution of the problem .

What is a Loop ?

A loop is defined as a block of processing steps repeated a certain

number of times. An endless loop repeats infinitely and is always

the result of an error.

Figure 1.17 illustrates a flowchart showing the concept of

looping. It shows a flowchart for printing values 1, 2, 3..., 20.

In step 5 of Figure 1.17, the current value of A is compared

with 21. If the current value of A is less than 21, steps 3 and 4 are

repeated. As soon as the current value of A is not less than 21,

the path corresponding to "NO" is followed and the repetition

process stops.

Flowchart Techniques 33

Terms Used in Looping:

Initialisation

Figure 1.17 Concept of looping

It is the preparation required before entering a loop. In Figure

1.17, step 2 initialises the value of A as 1.

Incrementation It is the numerical value added to the variable

each time one goes round the loop. Step 4 in Figure 1.17 shows

the increment of A by 1.

A < 21

YES

IS NO

BEGIN

A (A + 1)

END

A = 1

PRINT A

STEP 1

STEP 2

STEP 3

STEP 4

STEP 5

34 Flowcharting Concepts and Algorithms

Figure 1.18 Flowchart for calculating the salary of 100 workers

COUNT > 100

BEGIN

PAY WAGE x HOURS

COUNT = 1

STEP 1

STEP 2

END

HOURS

NAME, WAGE,

INPUT

NAME, PAY

COUNT COUNT + 1

STEP 3

STEP 4

STEP 5

STEP 6

STEP 7

YES

Flowchart Techniques 35

The Loop Variable It is an active variable in a loop. In Figure 1.17,

A is an active variable.

Loop Exit Test There must be some method of leaving the loop

after it has revolved the requisite number of times. In Figure

1.17, step 5 is the decision diamond, where the value of A is compared

with 21. As soon as the condition is satisfied, control comes

out of the loop and the process stops.

Example 1.10

Draw a flowchart for calculating the salary of 100 workers in a

factory.

Solution

Figure 1.18 represents the flowchart. In Figure 1.18, step 2 is for

initialisation of the value of COUNT where COUNT is an active

variable. Step 7 is the incrementation. Step 3 is for the EXIT test.

Steps 4 to 6 are the repetitive steps in the loop to input the

NAME, WAGE and HOURS, and then calculate the value of PAY

in step 5 and print the name and pay in step 6.

In step 7, the value of COUNT is increased by 1 and the current

value of COUNT is compared with 100 in step 1. If it is more

than 100, the process is halted.

Exercise 1.1

Q 1. How many records will be read by the flowcharts, shown in

Figures 1.19 and 1.20.

Q 2. A certain file contains 15 records. Which of the flowcharts

shown in Figures 1.21 and 1.22 read 15 and only 15

records?

Q 3. The formula to compute simple interest I on a loan of

rupees P at an interest rate R for T years is given as

Draw a flowchart to input the values of P, R and T and to

calculate the value of interest I. Also print the values of P,

R, T and I.

I = PRT

100

36 Flowcharting Concepts and Algorithms

Q 4. The flowchart shown in Figure 1.23 is drawn to print the

sum of integers 1 to 100. What changes would you make in

this flowchart, if the SUM for the first 100 odd integers is

required? Redraw the flowchart.

Figure 1.19 Reading of records

BEGIN

I = 0

READ K

I < 10

END

YES

I + 1

Flowchart Techniques 37

Figure 1.20 Reading of records

Q 5. Consider an equation Y=X2+2X+3. Draw a flowchart which

gives a method for calculating the values of Y for different

values of X varying from -4 to +4 in steps of 1 and prints

each value of X and the corresponding value of Y.

BEGIN

I = 0

READ K

I < 10

END

YES

I + 1

38 Flowcharting Concepts and Algorithms

Figure 1.21 Counting of records

BEGIN

I = 0

READ

I = 15

END

YES

RECORD

I + 1

Flowchart Techniques 39

Figure 1.22 Counting of records

1.3.3 Counting

Counting is an essential technique used in the problem solving

process. It is mainly for repeating a procedure for a certain number

of times or to count the occurrences of specific events or to

generate a sequence of numbers for computational use. Since a

BEGIN

I = 0

READ

I > 15

END

YES

I + 1

RECORD

40 Flowcharting Concepts and Algorithms

Figure 1.23 Calculating sum of integers 1 to 100

computer cannot count by itself, the user has to send the necessary

instruction to do so. The counting process is illustrated in

the flowchart shown in Figure 1.24

Here I is a counter which is initialised to a value zero in step

2. In step 3, a NAME is read and stored in the memory of the

BEGIN

PRINT SUM

A < 101

END

YES

A + 1

SUM = 0

A = 1

SUM SUM + A

Flowchart Techniques 41

Figure 1.24 Counting process

computer. The value of the counter is incremented by 1 in step 4.

In step 5, the NAME is printed from the memory of the computer.

In step 6, a check is made on the value of I. If the current value of

I is less than 5, the cycle is repeated from steps 3 to 5. If the value

of I is equal to or more than 5, the process of reading and printing

NAME stops. Using this type of flowchart we can read and print

the NAME five times.

BEGIN

I < 5

END

YES

(I + 1)

I = 0

READ NAME

PRINT NAME

STEP 1

STEP 2

STEP 3

STEP 4

STEP 5

STEP 6

STEP 7

42 Flowcharting Concepts and Algorithms

Example 1.11

Which numbers will be printed by the flowcharts shown in Figures

1.25 and 1.26 respectively?

Figure 1.25 Flowchart for printing numbers

Solution

(a) In Figure 1.25, the value of I is initialised to zero in step 2.

In step 3, the value is incremented by 1, i.e. it is 1. In step 4

BEGIN

I = 0

PRINT I

I > 5

YES

END

I + 1

STEP 1

STEP 2

STEP 3

STEP 4

STEP 5

STEP 6

Flowchart Techniques 43

Figure 1.26 Flowchart for printing numbers

I is printed. In step 5, the current value of I is compared

with 5. Since the current value of I is 1 and 1 is not greater

than or equal to 5, the control is transferred to step 3. Steps

3 and 4 are repeated again till the current value of I is 5.

Thus, the values of I that are printed would be 1, 2, 3, 4, 5.

(b) In Figure 1.26, the value of I is initialised to 1 in step 2. The

number 1 is printed in step 3. In step 4, the value of I is

increased by 1. So the current value of I is 2. In step 5, 2 is

compared with 5. Since 2 is less than 5, so the control is

BEGIN

I = 1

PRINT I

I < 5

END

YES

I + 1

STEP 1

STEP 2

STEP 3

STEP 4

STEP 5

STEP 6

44 Flowcharting Concepts and Algorithms

transferred to step 3 and the number 2 is printed. This

cycle repeats and numbers 3 and 4 are printed. When the

current value of I reaches 5, the control is transferred from

step 5 to 6. Thus the numbers printed are 1, 2, 3 and 4.

Exercise 1.2

Q 1. Which numbers will be printed using the flowcharts shown

in Figures 1.27 and 1.28 respectively.

Figure 1.27 Printing of numbers

BEGIN

I = 0

PRINT I

I < 5

END

YES

I + 1

Flowchart Techniques 45

Q 2. Write a flowchart to print the following sequence of numbers.

(a) 20, 19, 18, 17,...., 1.

(b) 2, 4, 6, 8,....., 32.

Q.3 In the flowchart shown in Fig 1.29, the following data is

inputted.

Figure 1.28 Printing of numbers

BEGIN

I = 0

PRINT I

I > 5

END

YES

I + 1

46 Flowcharting Concepts and Algorithms

Figure 1.29 Flowchart for Q. 3 in Exercise 1.2

BEGIN

END

SOLD

VALUE OF GOODS

INPUT

SALES MAN’S

NAME

VALUE < 500

VALUE > 500

SALES MAN’S NAME,

VALUE OF GOODS

PRIINT:

SOLD,

WAGE.

WAGE 50 +

10 % OF VALUE

WAGE 80 +

YES

Flowchart Techniques 47

Input Data

Salesman’s Name Value of goods sold

(a) Mohan 1500

(b) Shyam 2100

Calculate the value of wage in each case and give the result

of the print statement.

1.3.4 Counting for Controlling a Loop

Sometimes, it is essential to repeat a process for a specific number

of times only. In such a case, there are two standard techniques

used. These technique are as follows:

Technique 1

In this technique, we use the following six steps.

1. Initialise a counter to 0, i.e. COUNT = 0. Input value of N

where N stands for the number of times a loop is to be

repeated.

2. Increase the counter by 1. or COUNT = COUNT + 1

3. Test the value of counter and compare the current value

with N. If the current value of the COUNT is greater than

N, then branch off to step 6, otherwise continue.

4. Carryout the sets of instructions (procedure).

5. Go back to step 2.

6. End the loop and continue further programming. These six

steps are shown in Fig 1.30.

Technique 2

1. In this method, the counter is first initialised to zero and

the value of N is inputted.

2. Carry out the sets of instructions of the program.

3. Increase the counter by 1.

4. Test the counter. If COUNT < N then Go to step 2.

5. ELSE END

The above mentioned six steps are represented pictorially by the

flowchart shown in Figure 1.31.

48 Flowcharting Concepts and Algorithms

Figure 1.30 Flowchart for controlling a loop (Technique 1)

Sometimes, it may be necessary to repeatedly use any of the

above two techniques in order to solve a specific problem. This is

called nested loop. It means that we have the first loop and

within this loop, there is another loop. Solving a problem using

the nested loop technique is very helpful for a multidimensional

array.

BEGIN

END

INPUT N

COUNT > N

SET OF

INSTRUCTIONS

COUNT = 0

COUNT COUNT + 1

YES

STEP 1

STEP 2

STEP 3

STEP 4

STEP 6

STEP 5

Flowchart Techniques 49

Figure 1.31 Flowchart for controlling a loop (Technique 2)

1.4 Procedure for Problem Solving

Though every problem is an entity in itself, there are a few basic

steps that should be understood and followed for effectively solving

a problem using computer techniques. On following these

steps, your problem solving capacity will improve. There are

basically six steps in solving a problem. These are:

BEGIN

END

INPUT N

COUNT < N

SET OF

INSTRUCTIONS

COUNT = 0

COUNT COUNT + 1

YES

STEP 1

STEP 2

STEP 3

STEPS 4 & 5

STEP 6

50 Flowcharting Concepts and Algorithms

1. First, spend sometime in understanding the problem thoroughly.

In this, you are not required to use a computer.

Instead try to answer and solve the problem manually.

2. Now construct a list of variables that are needed to solve

the problem.

3. Once you have completed step 2, you have to decide the

layout for the output format.

4. Next, select the programming technique which is best

suited to solve the problem and carryout the coding.

5. Test your program. Choose some test data so that each part

of the program is checked for correctness.

6. Finally use the data validation program to guard against

processing of wrong data.

The above six steps are further explained in the following paragraphs.

1.4.1 Step 1. Understanding the Problem

Read each statement in the problem carefully, so that you can

answer the first question "What is expected by solving the problem?"

Do not start drawing a flowchart straight away. Instead,

read each statement of the problem slowly and carefully,

understanding the keywords. Take a pencil and paper and try to

solve the problem manually for some test data. Let us understand

this point by solving the problem, given in Example 1.12.

Example 1.12

Write a flowchart to accept a value M and find the sum of first M

even integers.

Solution

The solution of this problem requires you to draw a flowchart so

that if you input 6 as the value of M, the flowchart should get you

the sum of first 6 even integers. In the first step, you should be

able to answer the following two questions.

"What are the first 6 even integers?"

These are 2, 4, 6, 8, 10, and 12.

"What is their sum?"

Flowchart Techniques 51

The sum is 42. Hence the flowchart is to be so framed that the

sum of first 6 even integers comes out to be 42.

1.4.2 Step 2. Construction of the List of Variables

In this step, you should think in advance the number of variables

and the names of the variables before drawing a flowchart. The

names chosen for variables should be an aid to memory. For

example, in the case of the problem stated in step 1 above, the

variables may be, I, SUM and COUNT as given below.

1. Generate even integers 2, 4, 6,...(I)

2. Total the sum of even integers 2+4+6+... (SUM)

3. Count the number of even integers, i.e. COUNT 1, 2, 3,...

(COUNT)

Thus, it is clear that we need to use the above three variables

and one more variable "M" whose value will be inputted from the

keyboard. Hence the four variables are:

M Which is to be inputted from the keyboard.

I Which is to generate even integers.

COUNT A counter to keep a track of the number of even integers

that have been summed.

SUM An accumulator that contains the current total of the

even integers.

1.4.3 Step 3. Output Design

Sometimes, the ‘output’ format is specified in the problem, but

most of the times, it is not so. If the output format is not specified,

we must keep in mind that the output report should be easily

understandable by a reader. The headings should not cause any

ambiguity in the mind of the reader.

In the problem of Example 1.12 and stated in step 1 above,

the output format could be as follows:

No of integers Total value

6 42

You should keep one point in mind. The programs and problem

solutions are for other people (teachers, supervisors, contrac52

Flowcharting Concepts and Algorithms

tors etc). They will give you credit only if they can understand the

results and analyse them. Hence, the output format should be

attractive, easy to read and self-explanatory.

1.4.4 Step 4. Program Development

You should now draw a flowchart for the procedure that you have

developed in steps 1 to 3 above. Standard symbols should be used

for drawing a flowchart. If a problem is complex, you should

divide it into different parts. Then draw a flowchart for each part

separately and join them together using connectors.

A flowchart for the problem in Example 1.12 and stated in

step 1 can be drawn as shown in Figure 1.32.

When a flowchart is drawn correctly, you can convert it into a

programme using any of the high level languages like BASIC,

COBOL, FORTRAN or PASCAL.

1.4.5 Step 5. Testing the Program

You should give a dry run to a program that translates the flowchart

of step 4. This means giving some known values to the

variables and checking the result. Test values are so selected that

each arm of the flowchart is tested and consequently the program

is confirmed to be free from logic errors.

1.4.6 Step 6. Validating the Program

It is quite likely that the user of your program may enter values,

which are not expected by the program. Such values should be

rejected by the procedure drawn by you. This is known as validation

of data program. For example, in the problem in Example

1.12 and stated in step 1 above, we may give the limit to the

value of "M" and "M" should be a numerical value. Such types of

checks can be included in our validation program.

1.5 Algorithm

The sequence of instructions for solving a particular problem is

known as algorithm. Constructing an algorithm to solve a given

problem requires a high degree of ingenuity. But once an

Flowchart Techniques 53

algorithm is laid out, it can be used by a person who does not

even know its purpose.

Figure 1.32 Flowchart to Example 1.13

BEGIN

INPUT M

I = 0

SUM = 0

SUM = SUM + I

COUNT = 0

I = I + 2

SUM, COUNT

COUNT > M

YES

COUNT

= COUNT + 1

END

54 Flowcharting Concepts and Algorithms

We shall write an algorithm to solve a quadratic equation

and compute its real roots.

Example 1.13

Compute real roots of a quadratic equation

Solution

Step 1

Read the values of the coefficients of X2, X and constant quantity,

i.e., the value of A, B and C and store them in the memory.

Step 2

If A = 0 and B = 0 then print "No root exists" and stop. Else continue.

Step 3

If A = 0 and B is not equal to 0, then root X1 = C/B. Write the

value of root and also write "Linear Equation" and stop. Else

continue.

Step 4

Compute (B2 4AC) and set D2 = B2 4AC

Step 5

If D = 0, then compute Root X1 = Root X2 =( B/2A), write values

of Root X1, Root X2 and stop. Else continue.

Step 6

If D < 0, then write "Roots are not real" and stop. Else continue.

Step 7

If D > 0, then calculate

Root X1 = ( B + (B2 4AC)/(2A))

Root X2 = ( B (B2 4AC)/(2A))

Ax2 + Bx + C = 0

Flowchart Techniques 55

1.5.1 Characteristics of the Instructions in an Algorithm

Write values of Root X1, Root X2 and stop.

The sequence of instructions must possess the following

characteristics for qualifying as an algorithm :

1. Each and every instruction should be precise and unambiguous.

2. Each instruction should be such that it can be performed in

a finite time.

3. One or more instructions should not be repeated indefinitely.

This ensures that the algorithm will ultimately terminate.

4. After performing the instructions, that is, after the algorithm

terminates, the desired results must be obtained.

Example 1.14

Let us consider another case where there are 50 students in a

class who have appeared in their final examination. Their marksheets

have been given. We are required to write an algorithm to

calculate and print the total number of students who have passed

in first division.

Solution

Step 1

Initialize TOTAL, FIRST_DIVISION and TOTAL MARKSHEETS_

CHECKED to zero.

Step 2

Take the marksheet of the first student.

Step 3

Check the division column of the marksheet to see if it is

FIRST_DIVISION : if no, go to step 5.

Step 4

Add 1 to TOTAL FIRST_DIVISION.

56 Flowcharting Concepts and Algorithms

Step 5

Add 1 to TOTAL MARKSHEETS_CHECKED.

Step 6

Is TOTAL MARKSHEETS_CHECKED = 50? : if no, go to step 2.

Step 7:

Print TOTAL FIRST_DIVISION.

Step 8:

Stop.

1.6 Programming

If we compare structured programming to building a house, then

structured programming is to build the house after the plan for

the house is drawn. We would like to build a house using standard

bricks, window-frames, doors etc., so that the house so constructed

is appealing and comfortable. Thus, structured

programming also contains three standard control structure.

These are:

Simple Sequence Simple Selection Simple Repetition

The above three structures are simple to use as they can be

recognised easily. They have one entry and one exit point and

they are free from any programming language used for coding a

solution of a problem. This is discussed in detail in section 1.8.

1.6.1 Modular (Top-Down) Program Design

You must have realised that an effective approach to follow in the

programming analysis stage of program development is to break

down a large problem into a series of smaller and more understandable

tasks. Thus, the programmer may first develop a

main-control program that is used to outline the major segments,

or modules, that are in turn needed to solve a problem. The

main-control program specifies the order in which each subordinate

module in the program will be processed. The programming

Flowchart Techniques 57

analysis stage continues until every module has been reduced to

the point that the programmer is confident that he or she has a

solution method that will solve the task.

When this modular (top-down) program design practice is

used, an instruction in the main-control program branches control

to a subordinate program routine (subroutine) or module.

When the specific processing operation performed by the module

is completed, another branch instruction may transfer program

control to another module or return it to the main-control program.

Thus, the modules or subroutines are really programs

within a program. Each module typically has only one entry point

and only one exit point. Some of the advantages of using this

construction option are:

(a) Complex programs may be divided into simpler and more

manageable elements.

(b) Simultaneous coding of modules by several programmers is

possible.

may be used in other programs as needed.

(d) The location of program errors may be more easily traced to

a particular module, and thus debugging and maintenance

may be simplified.

(e) Effective use can be made of tested subroutines prepared by

software suppliers and furnished to their customers.

1.6.2 Pseudo Code Revisited

Pseudo code is an abbreviated form of expression that makes use

of both the English language and certain programming language

control words such as IF - THEN - ELSE & END - IF.

The user describes in plain English language, the sequence of

steps necessary to solve a particular problem. Sentences are generally

written one per line. Indentation is used in the IF statement

to outline which actions are to be taken if a condition is true

and which are to be taken if the condition is not true.

Differences between PseudoCode and Flowchart

Pseudocode differs from the flowchart in the following ways:

58 Flowcharting Concepts and Algorithms

(a) Pseudocode is self-explanatory and does not require a separate

documentation. This is so because it is written in plain

English language.

(b) Pseudocode has a structure similar to that of a programme

written in BASIC or PASCAL language. But flowcharts

have a tendency to extend flow lines in all directions and

thus their paths of instructions do not parallel the final

BASIC code.

The following are some examples of flowcharts and their equivalent

pseudocode.

Example 1.15

Working with Masala Dosa Mincer

Figure 1.33 Flowchart for Example 1.15

BEGIN

TURN

MINCER ON

MINCE

DOSA MASALA

TURN

MINCER OFF

END

Flowchart Techniques 59

Pseudo code

BEGIN

Turn Mincer on

Mince dosa masala

Turn Mincer off.

END

This is a case of simple sequence. The flowchart is given in Figure

1.33

Example 1.16

In this example a flowchart for Drink selection is shown in Figure

1.34

Figure 1.34 Process of selection for example 1.16

Tea

Pour A Cup

Coffee

YES

Tea

Pour A Cup

60 Flowcharting Concepts and Algorithms

Pseudo Code

IF Tea

Then Pour a cup of Tea

Else Pour a cup of Coffee

Example 1.17

In this example, the flowchart and its equivalent pseudo code for

the process of repetition is shown in Figure 1.35.

Figure 1.35 Process of repetition and its pseudocode using While - End While loop

Example 1.18

Figure 1.36 illustrates the multichoice selection or the CASE

structure. In CASE structure selection can be made out of many

choices using the word CASE. CASE structures are used in evaluating

situations that can have a number of different results.

CASE in this sense refers to a refinement of a basic

IF-THEN-ELSE type of conditional structure (IF A is true, then

MINCE PASTE

YES

PASTE

NORMAL

FLOW CHART PSEUDO CODE

WHILE paste not Normal

Mince paste

ENDWHILE

Flowchart Techniques 61

do B), but a CASE structure functions more like a series of nested

IFS (IF A, then do this; if B then do that...). For example if you

have three types of drinks, then the flowchart shown in Figure

1.36 gives a method of selecting any one of them. This can also be

written in pseudocode form using CASE statement.

An equivalent Pseudocode of the flowchart shown in Figure

1.3.6 is given below:

Figure 1.36 Flowchart for case or multichoice selection

CASE drink

Lemon

Pour juice into glass from Lemon jug.

Orange

Pour juice into glass from Orange jug.

Pineapple

Pour juice into glass from Pineapple jug.

END CASE

DRINK

Lemon Pineapple

Orange

Pour Juice

Into Glass

From

Lemon Jug

Pour Juice

Orange Jug

From

Into Glass

From

Pineapple Jug

Into Glass

Pour Juice

OFFER DRINK

62 Flowcharting Concepts and Algorithms

REPEAT - UNTIL LOOP Structure

Example 1.19

In this example REPEAT - UNTIL loop structure is used. This

loop structure is an alternate to While - End While Loop.

Suppose you want to insert a nail in the wall by hitting its

head with a hammer. Then the flowchart representation and its

equivalent pseudo code will be as follows:

Pseudo code for Figure 1.37

REPEAT

Hit head of nail

UNTIL nail fully in

Figure 1.37 Flowchart for repeat-until loop of inserting a nail in the wall

An equivalent of the above flowchart using WHILE - END

WHILE structure will be as follows:

WHILE Nail is not fully in

Hit nail head with hammer

END WHILE

Flowchart for this pseudocode is shown in Figure 1.38.

Hammer

Yes

Nail

Completely

With

Hit Nail

Flowchart Techniques 63

Figure 1.38 Flowchart for While-End While loop of inserting a nail in the wall

Exercise 1.3

Figure 1.39 Flowchart for Q. N. 1

Q.1 A certain file contains 5 data records. Which of the

Hammer

Yes

Nail

Completely

With

Hit Nail

BEGIN

END

READ RECORD

I < 5

YES

I 0

I I + 1

64 Flowcharting Concepts and Algorithms

Figure 1.40 Flowchart for Q. N. 1

flowcharts shown in Figures 1.39 and 1.40 will read 5 and

only 5 data records?

Q 2. How many records will be read by each of the following

flowcharts? (see Figure 1.41 and 1.42)

Q 3. Consider the flowchart shown in Fig.1.41.

Find out the output if the input values of X,Y and Z are as

follows.

(a) X=7, Y=9, Z=11

(b) X=11, Y=9, Z=7

Q 4. Draw a flowchart that interprets the following statements.

(a) If SALES is 10,000 or more then

BONUS= 3% of SALES

(b) If SALES is 10,000 or more then

BONUS=3% of SALES ELSE

BONUS=2% of SALES.

BEGIN

END

READ RECORD

I > 5

YES

I 0

I I + 1

Flowchart Techniques 65

Figure 1.41 Flowcharts for Q N. 2

Figure 1.42 Flowchart for Q. N. 2

BEGIN

END

READ RECORD

N > 7

N 1

N N + 1

YES

BEGIN

END

READ RECORD

N > 7

N 0

N N + 1

YES

66 Flowcharting Concepts and Algorithms

Figure 1.43 Flowchart for Q.N.3

Q 5. What is the value of SUM for the flowchart shown in Figures

1.44 and 1.45.

Q 6. What is an algorithm? Write algorithms for each of the following:

(a) Formatting a disk in your computer.

(b) Finding a book in the library.

BEGIN

END

X < Y

YES

INPUT

X, Y, Z

YES

Y < Z

IS NO

BONUS =

1000

BONUS =

1500 2000

BONUS =

BONUS

Flowchart Techniques 67

Figure 1.44 Flowchart for Q No. 5

Q 7. The following steps are written to calculate the standard

deviation for any given numbers. Use this algorithm to calculate

the standard deviation for the numbers 8, 10, 12, 16,

19:

1. Find the sum of the list of numbers.

2. Divide the sum by the total number of numbers to

obtain the mean.

3. Subtract the mean from each number in the list and

square this result.

4. Calculate the sum of the squares found in step 3.

5. Divide the sum of step 4 by the total number of numbers

in the original list.

6. Find the square root of the result found in step 5.

This number is known as the standard deviation of the

original list.

BEGIN

END

M > 5

SUM 0

YES

M 1

SUM

SUM SUM +

M M + 2

68 Flowcharting Concepts and Algorithms

Figure 1.45 Flowchart for Q No. 5

Q 8. Write an algorithm to compute a sales person’s commission

based on the following table:

Amount Sales Commission (% of sales)

Under Rs. 500 2%

Rs. 500 or more

but under Rs. 5000 5%

Rs. 5000 and above 10%

Q 9. Draw the flowchart for the following pseudocode:

BEGIN

Input mortgage amount

IF amount < 25,000

BEGIN

END

M > N

M 1

YES

SUM 0

SUM

SUM = SUM +

M M + 1

INPUT N

Flowchart Techniques 69

THEN

down payment = 3% of amount

ELSE

payment 1 = 3% of 25,000

payment 2 = 5% of (amount - 25,000)

down payment = payment 1 + payment 2

END IF

print down payment

Q 10. Salesman’s commission is calculated using the following

Pseudocode. Use this for writing a flowchart.

Input sales

IF sales < 500

THEN

Commission = 2% of sales.

ELSE

Commission = 5% of sales.

END IF

Print Commission

Q 11. Convert the flowchart shown in Figure 1.46 into a pseudocode

for finding the largest of three numbers.

Figure 1.46 Flowchart for Q No. 11

START

END

N1 > N2

INPUT N1,N2,N3

N2 < N3 N1 > N3

PRINT N2 PRINT N3 PRINT N1

YES

YES YES

70 Flowcharting Concepts and Algorithms

Q 12. The pseudo code for the year and bonus is given below.

Draw a flowchart corresponding to this pseudo code.

INPUT employee number, pay, position code & years.

IF position code = 1

THEN set bonus to 1 week’s pay

ELSE IF position code = 2

THEN

IF 2 weeks pay > 700

THEN

set bonus to 700

ELSE

set bonus to 2 week’s pay

END IF

ELSE

set Bonus to 1.5 week’s pay.

END IF

IF year greater than 10

THEN

Add 100 to bonus

ELSE

IF years less than 2

THEN

cut bonus to half

ELSE

bonus stays the same.

END IF

Print employee number & bonus.

1.7 Programming Methods

1.7.1 Top-down Design

Top-down design is the technique of breaking down a problem

into the major tasks to be performed. Each of these tasks is then

further broken down into separate subtasks, and so on until each

subtask is sufficiently simple to be written as a self contained

module or procedure. The program then consists of a series of

simple modules.

Flowchart Techniques 71

In top-down design we initially describe the problem we are

working on at the highest, most general level. The description of

the problem at this level will usually be concerned with what

must be done not how it must be done. The description will be

in terms of complex, higher-level operations. We must take all of

the operations at this level and individually break them down

into simpler steps that begin to describe how to accomplish the

tasks. If these simple steps can be represented as acceptable

algorithmic step, we need not refine them any further. If not, we

refine each of these second level operations individually into still

simpler steps. This stepwise refinement continues until each of

the original top-level operations has been described in terms of

acceptable shortest (primitive) statements.

Advantages of Top-down approach

(a) It allows a programmer to remain "on top of" a problem and

view the developing solution in context. The solution always

proceeds from the highest levels down. With other techniques

we may find ourselves bogged down with very lowlevel

decisions at a very early stage. It will be difficult to

make these decisions if it is not clear how they may affect

the remainder of the problem.

(b) It is a very good way to delay decisions on problems whose

solution may not be readily apparent. At each stage in the

development, the individual operation will be refined into a

number of more elementary steps. If we are not sure how to

proceed with step 1 we can still work on step 2.

have made it easier to share problem development. For

example, one person may solve part 2 of the problem and the

other person may solve part one of the problem.

(d) Since debugging time grows so quickly, it will be to our

advantage to debug a large program as a number of smaller

units rather than one big chunk. The top-down development

process specifies a solution in terms of a group of smaller,

individual subtasks. These subtasks thus become the ideal

unit of program testing and debugging.

By testing the program in small pieces, we greatly simplify

the debugging process. In addition, we will have the

satisfaction of knowing that everything we have coded so far

is correct. When we add a new piece of code, say "p" to the

72 Flowcharting Concepts and Algorithms

overall program "P", and an error condition occurs, we can

definitely state that the error must either be in "p" itself or

in the interface between "p" or "P", because "P" has been

previously checked and certified.

(e) Another advantage of the top-down development process is

that it becomes an ideal structure for managing the implementation

of a computer program using teams of programmers.

A senior programmer can be responsible for the design

of a high-level task and the decomposition into subtasks.

Each of those subtasks can then be "farmed out" to a more

junior programmer who work under the direction of the

senior staff. Since almost all software projects are done by

teams of two or more programmers, this top-down characteristic

is very important.

In summary, top-down programming is a program design

technique that analyses a high-level problem in terms of more

elementary subtasks. Through the technique of stepwise refinement

we then expand and define each of these separate subtasks

until the problem is solved. Each subtask is tested and verified

before it is expanded further. The advantages of this technique

are:

(a) Increased intellectual manageability and comprehension.

(b) Abstraction of unnecessary lower-level detail.

they are actually needed.

(d) Reduced debugging time.

1.7.2 Bottom-up Design and Implementation

When faced with a large and complex problem, it may be difficult

to see how the whole thing can be done. It may be easier to attack

parts of the problem individually, taking the easier aspects first

and thereby gaining the insight and experience to tackle the

more difficult tasks, and finally to try and bolt them all together

to form the complete solution. This is called a bottom-up

approach. It suffers from the disadvantage that the parts of the

program may not fit together very easily. There may be a lack of

consistency between modules, and considerable re-programming

may have to be done.

Flowchart Techniques 73

1.7.3 Modular Design and Programming

In industry and commerce, the problems that are to be solved

with the help of computers need thousands or even more number

of lines of code. The importance of splitting up the problem into a

series of self-contained modules then becomes obvious. A module

should not exceed about 100 or so lines and should preferably be

short enough to fit on a single page.

Advantages of modular design

(a) Some modules will be standard procedures used again and

again in different programs or parts of the same program.

(b) Since module is small, it is simpler to understand it as a unit

of code. It is therefore easier to test and debug, especially if

its purpose is clearly defined and documented.

modules can be quickly identified and changed.

(d) In a very large project, several programmers may be working

on a single program. Using a modular approach, each

programmer can be given a specific set of modules to work

on. This enables the whole program to be finished sooner.

(e) More experienced programmers can be given the more complex

modules to write, and the junior programmers can work

on the simpler modules.

(f) Modules can be tested independently, thereby shortening

the time taken to get the whole program working.

(g) If a programmer leaves part way through a project, it is easier

for someone else to take over a set of self contained modules.

(h) A large project becomes easier to monitor and control.

1.8 Structured Programming

In the 1960s in the USA a number of surveys confirmed what

most data processing managers had believed for a long time

that there is a substantial variation in programmer abilities and

that too much time is spent on debugging programs and on

maintenance activities. The surveys generated much controversy,

but the effect they had was dramatic. Suddenly everyone

became concerned with the programmer’s productivity and the

74 Flowcharting Concepts and Algorithms

way in which he actually programmed. In 1965, Professor Dijkstra

of Eindhoven University in Holland presented a paper at the

IFIP Congress in New York suggesting that the GOTO statement

should be eliminated from programming languages altogether,

since a program’s quality was inversely proportional to the number

of GOTO statements in it. In the following year, Bohm, and

Jacopini showed that any program with single entry and exit

points could be expressed in terms of three basic constructs:

(a) Sequence or carrying out a process

(b) Iteration or looping

This was the beginning of structured programming. This

dramatically improved the quality of programming and of programmer

productivity. The above three constructs have been

explained in sections 1.2 and 1.6.2.

There is no doubt that structured programming has been

successful, but it does not solve all our problems. Poorly constructed

system designs can still negate the benefits provided by

structured programming. It was not surprising then that similar

principles were applied to the tasks of analysis and design and a

full range of structured methods came into being.

1.8.1 Why Structured Programming ?

In computer programming, the spaghetti code is the method of

coding that confuses the program flow because of the excessive

use of GOTO or jump statements. Hence one of the major

improvements has been the shift from spaghetti code to TOPDown

modular design and structured programming methods.

The reason for the evolution to structured programming is the

need for well organized programs that are ultimately easier to :

(a) Design

(b) Read and understand

(d) Test and Debug

(e) Combine with other programs

Writing programs that are clear for any programmer to read

and understand is a very important consideration, particularly if

there is a change in programming personnel.

Flowchart Techniques 75

1.8.2 Characteristics of Structured Programs

In general terms, structured programming is the development of

computer programs that are well organized. Here is a list of

characteristics of structured programs.

(a) The programs are based on top-down modular design. In

other words, the problem at hand is analysed or broken

down into major components, each of which is again broken

down if necessary. Therefore, the process involves working

from the most general down to the most specific. The design

of the modules is reflected in hierarchy charts such as the

one shown in Figure 1.47.

Figure 1.47 Top-Down modular Design

Driver

module

INPUT pay

Gross

pay

Net OUTPUT

FET FICA NJIT

Title

INPUT monthly

Calculate

module

Driver

Data Column heads payment

Calculations

for detail

lines Totals

Detail

lines

76 Flowcharting Concepts and Algorithms

(b) Each module has one entry point and one exit point. The

GOTO statement is never used to jump from one module in

the program to another. (Pure structured programs do not

use GOTO). The following program in BASIC is an example

of structured programming:

340 REM * * * * * * * INPUT DATA * * * * * * * * * * *

350 PROMPTS WILL SHOW ON THE SCREEN DATA WILL BE ENTERED

AT KEYBOARD

360 CLS : ′ CLEAR SCREEN

370 OK$ = "N"

380 WHILE OK$ = "N"

390 INPUT "ENTER THE EMPLOYEE NAME"; EMPNAME$

400 INPUT "ENTER THE HOURS WORKED"; HOURS

410 INPUT "ENTER THE RATE PER HOUR"; RATE

420 INPUT "ENTER THE NUMBER OF EXEMPTIONS"; EXMP

430 INPUT "ENTER THE SALARY TO DATE"; SALDATE

440 PRINT: PRINT

450 INPUT "ENTRIES OK (Y OR N)"; OK$

460 WHILE OK$ <> ‘‘Y’’ AND OK$ <> ‘‘N’’

470 INPUT "PLEASE ENTER A ‘Y’ OR AN ‘N’ " ; OK$

480 WEND

490 WEND

500 RETURN

one half page long. If they are longer than this, they should

preferably be split into two or more submodules.

(d) Two-way decision statements are based on IF..THEN,

IF..THEN..ELSE, and nested IF statements.

(e) Loops are not custom designed with the use of the GO TO

statement, but are based on the consistent use of

WHILE..WEND and FOR..NEXT. In WHILE..WEND, the

loop is based on the truth of a condition, and in FOR..NEXT,

on a counting process, and the number of repetitions that

can easily be predicted. (See Figure 1.48)

1.8.3 Other Characteristics of "GOOD" Programs

Readability

The ease with which some one can read a program is based on the

Flowchart Techniques 77

Figure 1.48 GO TO statements are removed

manner in which it has been typed. This includes printing gaps

between the modules.

Documentation

The documentation is greatly improved if the variable choice is

descriptive. This serves as a mnemonic device to aid in remembering

the meaning of the variables.

Efficiency

The speed of execution is something to consider, but it is not a

primary concern when using a particular programming language.

In terms of the manipulation of numbers, integers are the fastest,

followed by single precision, with double precision being the

slowest.

1.8.4 Importance of Structured Programming

Structured programming is important for the following reasons:

(a) It is much easier for students to debug structured programs

and for instructors to grade them.

Title

INPUT monthly

Calculate

module

Driver

Data Column heads payment

Calculations

for detail

lines Totals

Detail

lines

GO TO

78 Flowcharting Concepts and Algorithms

(b) Students who learn top-down modular design retain what

they have learned over a much longer period of time.

and/or structured COBOL are better prepared for these languages.

1.9 Modularity

One way to improve the structure of a program is to break down

the original problem to be solved into independent tasks (*called

modules in pseudocode and subroutines in BASIC) and then

execute these modules in a predefined sequence. The resulting

design consists of a network of modules.

Breaking down a problem into smaller pieces (modules)

allows you to focus more easily on a particular piece of the problem

without worrying about the overall problem. The tasks

become easier to solve and are more manageable since each

performs a very specific function. Typically, you can code each

module independently of the others and test or debug each module

separately. Once all modules are working properly, you can

link them together by writing the coordinating code (generally

called the root segment or the main code). The coordinating code

activates the various modules in a predetermined sequence. Consider

Figure 1.49, which illustrates these principles. Note that

the resulting program consists of five modules: the coordinating

module and the four modules A, B, C, and D. It is, of course,

conceivable that a particular module itself might be broken down

into other modules.

By breaking down a problem into independent modules, a

programmer in charge of a very complex problem can easily

assign various members of a team the responsibility for developing

one or more modules. Such modules can be run and tested

independently of one another. Making one change in one module

is a very local intervention that does not require an understanding

of all other modules. In contrast, making one change in a

nonmodular program held together by myriads of GOTO

statements not only requires an understanding of the whole program

but can also produce masses of error messages and a lot of

unwanted output.

Another advantage of a modularized design is that you will

find yourself using the GOTO statement less frequently. This in

Flowchart Techniques 79

Figure 1.49 Program Decomposition

itself is very important, since the undisciplined use of the GOTO

statement can often give rise to the ‘‘spaghetti code syndrome’’,

which makes it very difficult for the program reader to remember

where in the program he/she is coming from and where he/she is

going!

In a modular environment, each module can be respecified as

a sequence of smaller modules describing what is to be done at

increasing levels of detail. The technique of expanding a program

plan into several levels of detailed subplans and presenting the

program structure as a hierarchy of tasks is sometimes referred

to as top-down design. A hierarchy chart, sometimes called a

structured diagram, is a useful tool for illustrating module relationships

and hierarchies. Figure 1.50 shows a hierarchy chart

for the problem shown in Figure 1.49

In summary, modularization helps the programmer write

better structured programs that are generally more compact and

thus easier to work with and more readable. A subroutine can

also reduce the code required for writing tasks that are to be performed

repeatedly at different places in a program.

Problem

Coordinating code

Module B

Module D

Module A

Module C

Carry out A

Carry out B

Carry out C

Intial problem Carry out D

(task) Decomposition into

unrelated subtasks

A,B,C, and D

Independent modules are activated

by the coordinating module.

Each module returns control

to the coordinating module.

Coordinating Module

80 Flowcharting Concepts and Algorithms

Figure 1.50 A Hierarchy Chart

1.10 Programming Tools

These are the programs specially designed for the benefit of programmers

so that they can formulate the instructions to solve a

problem properly and easily. One of the important tools is editor.

This is explained in the following paragraphs.

1.10.1 Editors

An editor is a piece of software which enables the programmer to

enter and edit a program. The different kinds of editors are as

follows:

(a) Screen editor

(b) Line editor.

(d) Text editor

Screen editor

A screen editor allows the programmer to position the cursor

anywhere on the screen and insert or delete text.

Line Editor

A line editor allows lines of text to be entered and edited only

Coordinating

Module

A B C D

Flowchart Techniques 81

by entering commands which refer to a particular line or block of

text. This type of editor was used in the days before VDU screens

were common, when the lines typed in were printed out on a

piece of paper as well as being stored in the memory. An example

of a line editor is EDLIN which is supplied with MS-DOS. This

editor is suitable for typing in small amounts of text such as

batch files. Typical commands include:

Line Number Edits the line specified

A Appends the line

D Delete line

I Insert line

L List text

E End editing

Linkage Editor

The linkage editor is a utility program which adapts a program

that has just been assembled or compiled into a particular computer

environment. It formally links cross references between

separate program modules, and it links the program to various

libraries containing prewritten subroutines. The output of a

linkage editor is a load module, a program ready to run in the

computer.

Text Editor

A text editor is a software program that creates and manages

text files. Text editors are used to create and edit source language

programs, data and text files. Unlike word processors, text

editors do not have elaborate formatting and printing features.

For example, there is usually no automatic word wrap or underline,

bold face and italics printing in text editors.

1.10.2 Other Program Development Aids

Some of the other aids for a programmer may include

(a) An on-line help facility giving information about any command,

standard function or procedure.

(b) Utility programs enabling the user to design input screens

and have the code automatically generated.

82 Flowcharting Concepts and Algorithms

to build up a precompiled tested code.

(d) An integrated development environment combining a text

editor and a compiler with pull down menus, windows, help

facility and debugger.

(e) Application generators These are the software programs

that generate application programs from a description of the

problem rather than from detailed programming. Application

generators are one or more levels higher than the programming

language, whose source code they generate, but

still require the user to input basic mathematical

expressions in order to state complex processing on their

business data. For example, a complicated pricing routine

will require that the pricing algorithms be stated just as

they would be in any programming language.

1.10.3 Types of Program Errors

Once a program has been typed in, different types of errors may

show up. These include:

(a) Syntax/semantic errors

(b) Logic errors

Syntax/semantic errors

Syntax is a set of rules governing the structure of and relationship

between symbols, words and phrases in a language statement.

A syntax error occurs when a program cannot understand

the command that has been entered.

Logic errors

Logic refers to a sequence of operations performed by a software

or hardware. Software logic or program logic is the sequence of

instructions in a program. Logic errors are the errors that have

been entered in the instructions created because of the mistake

made by a programmer. Suppose you wanted to do the sum of A

and B and put the result in the variable C. This is accomplished

by typing:

C := A + B

Flowchart Techniques 83

But while typing, the programmer has typed the following

expression:

C := A - B

Such a program will run properly but will give erratic result

because the value of C will not be the sum of A and B but it will

be the difference of A and B which is quite different. Such errors

can only be detected with the help of test data that will give the

input values of A and B and the resultant value that should come

out of the program as a result of the operation performed on A

and B. If the result given by the computer and the result calculated

manually with the help of a calculator are the same, then

you can say that there is no logical error. Otherwise a logic error

may be present in the program.

Runtime error

Runtime errors occur when a program is run on the computer

and the results are not achieved due to some misinterpretation of

a particular instruction. This could be some thing like dividing a

number by zero which results in a very large value of quotient. It

may also be any other instruction which a computer is not able to

understand. To overcome this problem, there is a built-in error

detector in the language interpreter or compiler which will give

the message and that will reflect the reason for the run time

error.

1.10.4 Program Testing

It is the job of the programer to test, as far as possible, that all

parts of the program work correctly. It should be realised that

complete testing is not possible except in the case of the most

trivial program; one can never be completely certain that all

errors have been removed, but sufficient tests can be performed

to give a reasonable measure of confidence in the program.

The situation is analogous to testing children on multiplication

tables; once a child has answered a certain number of multiplication

table tests correctly, at some point or other the teacher

assumes that all other tests will be answered correctly and

testing ceases.

84 Flowcharting Concepts and Algorithms

1.10.5 Designing a Test Plan

Good testing requires the following:

(a) A thorough knowledge and understanding of what the program

is supposed to do.

(b) Plan out in advance what ought to be tested.

(d) Writing out the test plan.

Since we cannot test everything, each test must be carefully

planned to provide more information about the program. A major

benefit of preparing a comprehensive test plan with expected

results is that it forces the programmer to think carefully about

the program and often errors are spotted even before running the

test.

1.10.6 Methods of Testing

The objectives of testing can be stated in two basic questions:

(a) Does the logic work properly? This means, answering the

following:

(i) Does the program work as intended?

(ii) Can it be made to crash?

(b) Is the necessary logic present? This means answering the

following:

(i) Are there any functions missing?

(ii) Does the program or module do everything specified?

There are two different ways of testing. These are:

(a) Functional testing

(b) Logical or structural testing

1.10.7 Functional Testing

Functional testing is carried out independently of the code used

in the program. It involves looking at the program specification

and creating a set of test data that covers all the inputs and outputs

and program functions. This type of testing is also known as

"black box testing". For example, to test the program that

calculates check digits we could draw up the following test plan:

Flowchart Techniques 85

Table 1.1 Test Plan for Check Digits

Serial Test for numer- Purpose Expected Actual

Number ical data result result

1 Enter 1234 Test validity of data 1234 Digits 3

2 Enter 8 digits Test extreme case are printed 3

as it is

3 Enter 123W Testing invalid data Data not Error

accepted

From Table 1.1 we will be able to make out whether the software

is testing the data correctly or not. If it is not testing properly,

then we may have to correct the program.

1.10.8 Logical ( Structural) Testing

Logical testing (white box testing) is dependent on the code

logic, and derives from the program structure rather than its

function. In other words, we study the program code and try to

test each possible path in the program at least once. The problem

with logical testing is that it will not detect the missing functions.

One method of devising a test plan is to start with a set of

functional test cases, and then add additional tests to exercise

each statement in the program at least once, making sure that

each decision is tested for all outcomes.

1.10.9 Debugging Aids

Once the presence of logic errors has been detected with the help

of test runs, there are various ways of finding where the error or

errors lie. These include the following:

(a) A dry run through the program, building up a trace table

while manually following the program steps.

(b) The inclusion of extra "write" statements to examine the

contents of variables at various points in the program.

(d) An ‘On line debugger’ which allows a programmer to step

through the program line by line and examine the values of

variables at any point in the program.

86 Flowcharting Concepts and Algorithms

1.10.10 Assembler

A program which translates an assembly language program into

a machine language program is called an assembler. An assembler

which runs on a computer for which it produces object codes

(machine codes) is called a self assembler (or resident assembler).

A less powerful and cheaper computer may not have enough software

and hardware facilities for program development and convenient

assembly. In such a situation, a faster and powerful

computer can be used for program development. The programs so

developed are to be run on smaller computers. For such program

development a cross assembler is required. A cross assembler is

an assembler that runs on a computer other than that for which

it produces machine codes.

1.10.11 Compiler

A program which translates a high-level language program into a

machine language program is called a compiler. A compiler is

more intelligent than an assembler. It checks all kinds of limits,

ranges, errors etc. But its program execution time is more, and

occupies a larger part of the memory. It has low speed and low

efficiency of memory utilization. If a compiler runs on a computer

for which it produces the object code, then it is known as a self or

resident compiler. If a compiler runs on a computer other than

that for which it produces object code, then it is called a crosscompiler.

1.10.12 Interpreter

An interpreter is a program which translates one statement of a

high-level language program into machine codes and executes it.

In this way it proceeds further till all the statements of the program

are translated and executed. On the other hand, a compiler

goes through the entire high-level language program once or

twice and then translates the entire program into machine codes.

A compiler is nearly 5 to 25 times faster than an interpreter. An

interpreter is a smaller program as compared to the compiler. It

occupies less memory space. It can be used in a smaller system

which has limited memory space. The object program produced

by the compiler is permanently saved for future reference. On the

Flowchart Techniques 87

other hand, the object code of the statement produced by an

interpreter is not saved. If an instruction is used next time, it

must be interpreted once again and translated into machine code.

For example, during the repetitive processing of the steps in a

loop, each instruction in the loop must be reinterpreted every

time the loop is executed.

1.10.13 Data Description Language

Data description language(DDL) is a language used to define

data and their relationships to other data. It is used to create

files, databases and data dictionaries.

Hierarchical and network database management packages

are used in large computers such as mainframes or mini computers.

In these systems, large database packages are controlled by

the database administrator whose job is to identify the logical

relationships that exist in an organization’s records. A special

data description language is used to retrieve the stored information.

Programming skills are needed by those who work with

these software products and DDL helps them to do the job more

efficiently.

1.11 What is Program Maintenance?

User requirements from a specific program do not remain static.

They change frequently in response to such factors as new laws,

new ideas, new products, or new computer facilities. Program

maintenance covers a wide range of activities including correcting

coding and design errors, updating documentation and test

data, and upgrading user’s support. In other words, maintenance

may be viewed as enhancement i.e. adding, modifying, or developing

the code to support changes in the specifications.

1.11.1 Why Program Maintenance?

Although software does not wear out like a piece of hardware, it

"ages" and needs to be updated for the following reasons:

(a) Errors are found that were not detected when the system

was tested initially. Even though the system was thoroughly

tested, errors or bugs often appear after the system has been

in use for some time.

88 Flowcharting Concepts and Algorithms

(b) A new function may have to be added to the system. For

example, the school management had initially asked for the

preparation of monthly report of those students who had not

paid their fee in time. But at a later date, the auditors or the

principal of the school needs a report of those students who

are defaulters in paying their fee for more than three

months so that their names can be struck from the school. In

such a case, the report format will need a change.

in the program and detected later. This will require

modifications in the program.

(d) The final reason for program maintenance is that the

requirements of the user change with time. For example,

programs that produce income tax returns have to be modified

almost every year because of changing tax laws.

1.11.2 Problem Areas in Program Maintenance

Two problem areas in program maintenance are:

(a) high cost of software, and

(b) errors caused due to modification in the original program.

High Cost of Software

Major problem with software maintenance is that the program

writing is labour intensive in nature. Human beings who write

programs are likely to make errors. For example the programmer

who was originally assigned the task of solving and coding the

program may not be available to modify this program at a later

date. Therefore, the new person who is given the job of modification

will have to study and understand the logic of the original

program and then only he can modify the program. This process

may involve more time, money, and there are more chances of

making errors. In such cases, it may be easier and economical to

rewrite a new program rather than amending the old one.

Errors Caused due to Modification in the Original Program

Alteration in the original program, no matter how slight, must be

manually introduced. There is no easy way of making sure that

the modifications made will not cause any errors elsewhere in

any of the subprograms or the main program. Using the old codes

Flowchart Techniques 89

depend mostly on the programmer’s ability to judge what the

code can and cannot do. Hence the program is to be thoroughly

tested after modification before implementation.

1.11.3 Impact of Software Errors

The quality of a software system depends on its design, development,

testing, and implementation. An important aspect of software

quality is its reliability. A program is reliable if, when used

in a reasonable manner, it does not produce failures that are

dangerous or costly. Software errors can cause failure of the system

or produce inaccurate results. Programmers should therefore

strive to design error free programmes. The software errors are

mainly due to design errors or specifications. Hence these are

also to be rechecked before studying the impact caused by the

errors.

1.11.4 The Problem of Software Modification

The basic problems of modifying software can be attributed to

time schedule and the user-need satisfaction. These are as follows:

Time schedule

Modification of a program may not be feasible within the time

schedule because of several reasons. The reasons may be nonavailability

of the right kind of manpower, improper documentation

of the old program or testing data. For such cases, the earlier

version of the software will have to be used till all the errors are

removed in the newer version after it has been tested thoroughly.

User-need Satisfaction

People who are using the program are the final evaluators of the

modification. Hence it should be found out whether these users

are now satisfied with the new version of the software or not.

Further how useful is the new software for them? How enthusiastic

are they about the friendliness and ease of working with

the new software? Answers to all these questions are to be

evaluated and implemented.

90 Flowcharting Concepts and Algorithms

1.11.5 Software Life-cycle

Every software has a life cycle, just as a living organism or a new

product. Commercial programs such as payroll, accounts, stock

control and other software share a common life cycle pattern. One

method of doing things may work well for a period of time. This

may last for several years. However, owing to expansion or

changes in the nature of the business, the economic environment,

the need to keep up with new technology or other factors, the

program may seem to be inadequate for future use. At this point

investigations are made, requirements are analyzed, and a new

specifications are proposed and a new program is developed. The

life cycle of the new program thus starts again.

Stages in Software Life cycle

Analysis of the Problem and laying down Specifications The problem

must be first defined and analyzed and the specifications of

input and the output should be prepared. Sometimes a systems

analyst is asked to prepare a feasibility study and the cost benefits.

Once these are accepted, the software design starts.

Design and Development The design stage involves a number of

tasks such as designing the output, input, files, database if

applicable, system controls and test plan. Input forms must be

designed, clerical procedures laid down and all aspects of the

design must be documented. In the development stage, there are

two aspects. First the program development and next the equipment

acquisition. The senior programmer will rewrite program

specifications to describe what each program in the system will

do and how it will do it. The equipment will be acquired and the

program will be tested on the computer system.

Testing and Debugging The program so developed will be tested

for conforming the specification laid down and the results

achieved. At the same time, if there are any bugs in the system,

these will be removed and programs are re-tested.

Implementation This is the stage when the new software becomes

operational. It is a critical phase of the project, requiring careful

timing, coordination and training of all the user departments.

Maintenance All software need to be maintained. It means, performance

monitored, modifications made if required, errors corrected,

documents kept up-to-date. If the system needs

Flowchart Techniques 91

major modification then the life-cycle starts again. It means, the

changes are done and the software development is once again

carried out.

Training the User

Since one purpose of the new software system is to change existing

procedures, training is crucial. All individuals have to

understand what is required by the new software system. After

the problems of installation have been resolved and the organization

has adjusted to the changes created by the new software

system, the operational stage begins. That is, the system now

operates on a routine basis. However, this routine does not mean

that it remains unchanged. There is a constant need for maintenance

and enhancements. Maintenance is required because programs

inevitably have errors that must be corrected when they

appear. As users work with the new software system, they will

learn more about it and will develop ideas for change and

enhancements. The system continues to evolve throughout its life

cycle.

1.11.6 Documentation and its Importance

Documentation provide a general outline as well a few specific

details of the overall program structure. The documentation of a

program is a continuous process. After successfully completing

the program, we must ensure that documentation is complete

and is in a finished, usable form. This includes both technical

documentation for the programmers who may be working with

and modifying the completed program and user-level documentation

for the users of the program.

A good user documentation is essential if a program is to be a

useful tool. Good technical documentation is essential for maintaining

a program. We may decide at a future date to add features

to the program, or we may have to find and correct errors in

the program, both of which can be virtually impossible if the

technical documentation is inadequate.

1.11.7 Aim of Program or System Documentation

The aims of documentation are:

92 Flowcharting Concepts and Algorithms

(a) To help in the design of the system by working to a set of

standards and having available a clear description of the

work done so far. The documentation needs to be kept upto-

date throughout the project.

(b) Good documentation ensures that everyone involved in the

system (system designers, programmers, and users) fully

understand how their aspect of the system will work. For

example, what data will be inputted and how, and what

information will be available from the system. This allows

any misunderstandings or disagreements to surface before

they become deeply entrenched in the system.

even though the programmers involved in the original

design or programming of the system may not be available.

It is essential that proper documentation is kept to enable a

newcomer to make necessary corrections, alterations or

enhancements.

1.11.8 Contents of a Document of a System

The following are the parts of a document of the system:

(a) An accurate and up-to-date system specification.

(b) System flowchart(s) or data flow diagrams showing the

inputs to the system, files required, processes to be carried

out, and output from the system.

system.

(d) Organization, contents and layout of each file used.

(e) Layout and contents of all output prints and displays.

(f) Current version of each program listing.

(g) Test data and expected results.

In addition, the following items of documentation will need to

be prepared.

(a) Clerical Procedure Manual

(b) Operating Instruction

Clerical Procedure Manual

This manual details the activities that the clerical staff will

undertake in preparing data for input to the system. For examFlowchart

Techniques 93

ple, batching documents and calculating hash totals. It will also

describe what action is to be taken when errors occur for

example, when a validation program reports errors.

Operating Instructions

This document gives the details to the computer operator of how

to run the program. It may include:

(a) Details of the procedure for starting the program.

(b) Details of disks and tapes required.

(d) The number of copies of each report, and who is to receive

the output.

(e) Backup procedures to be followed.

(f) Recovery procedures in the event of hardware failure.

Data Preparation Instructions

This will contain instructions on data entry, showing if necessary

how each field should be entered. For example, a date field may

be entered in various formats and the correct one needs to be

specified.

In a small system, written perhaps for a single user working

on a micro-computer, these three manuals may be combined into

one User Manual.

1.12 Data Flow Diagrams (DFD)

Data flow diagrams are used to emphasize the logical flow of data

through a system. The basic symbol is a circle or bubble and is

called a ‘transform’ since it identifies a function that transforms

data. Figure 1.51 illustrates a data flow diagram for a small

organization.

Data flow diagrams can be made at different levels. Symbols

are also used to denote logical conditions such as AND or an

exclusive OR. Figure 1.52 shows the logical AND and the exclusive

OR symbols used in a data flow diagram concerned with validating

input. Both the transaction input and the master file

input are required for the transform VALIDATE INPUT. One of

the inputs by itself is insufficient. As a result of VALIDATE

INPUT, either a rejected transaction or a valid transaction will

be produced. However, both cannot be produced since the output

94 Flowcharting Concepts and Algorithms

Figure 1.51 Data flow diagram for a small business organization

Figure 1.52 Data flow diagram for validating input data

form the transform is an exclusive OR.

The data flow diagrams shows the inputs and outputs clearly.

A data flow diagram for customer enquiry system is shown in

Figure 1.53. This data flow diagram has the basic elements

namely SOURCE, DATA, STORE and DESTINATION.

1.13 Structure Charts

A flowchart is a blueprint or a logical diagram of the solution of a

problem. As explained earlier, flowcharts use a standard set of

CUSTOMERS

SALESFORCE

FINANCE

Customer

information

CUSTOMERS

MANAGEMENT

EVERYTHING

Reports

Response

Enquiries

Financial

history

VALIDATE

INPUT

Master file

input

Rejected

transaction

AND OR

Accepted

transaction

Transaction

input

Flowchart Techniques 95

Figure 1.53 Data Flow Diagram for customer enquiry system

symbols and the actual operation to be performed is written

inside the symbol. The arrow coming out of the symbol indicates

which operations is to be performed next.

There are special types of flowcharts, called structure charts,

that restrict the types of allowable operations and inter connections

in order to produce well organized and readable diagrams.

Structure charts are thus pictorial representation of the design of

a system.

The flowcharting technique is useful primarily for macrolevel

or system flowcharts level where we are concerned with the

most general level of operations needed to solve a large problem.

Each element of a system flowchart would typically represent a

fairly large and complex manual, clerical or computer procedure

DATA STORE

SOURCE DESTINATION

PROCESS

Data

element

Dataflow 1

Dataflow 2

Dataflow 3

Dataflow 4

96 Flowcharting Concepts and Algorithms

for which an algorithm must be developed and implemented.

These individual procedures could be developed and represented

using an algorithmic language. However in a structured chart,

there is a sequence of process shown along with the hierarchy of

the process. These structure charts are used at the system design

phase. Table 1.2 highlights the differences between data flow

diagram and structure chart.

Table 1.2 Difference between data flow diagram and

structure chart

Sl. No. Data Flow Diagram Structure Chart

(1) In a data flow diagram only the In a structure chart the

process is shown but the sequence in which process is

sequence is not important to be done is also important

(2) In this case, the hierarchy or In this case, hierarchy of the

the ladder in which the process process is important

is to be executed is not important

(3) A data flow diagram is nor- A structure chart is normally

made at the system anal- mally made at the system

ysis phase. design phase.

1.13.1 Elements of Structure Chart

Structure charts have three basic elements. These are :

Module

It is a rectangular shape with the process name written in it.

Figure 1.54 shows a module. The box represents a module and

the alphabets such as A, B, C written inside the box are the

names of the processes performed.

Connectors

Connectors connect any two modules with the arrows drawn in

the downward direction. Figure 1.55 shows the arrow which is a

connector.

Flowchart Techniques 97

Figure 1.54 Module

Figure 1.55 Connector

Couple

The carriers of data are called couples. These indicate the data

flow between the modules. Figure 1.56 shows a couple. Couple

can be of two different types.

(a) Data couple

(b) Control couple

Module

(Process)

(Process) (Process)

Module

Connecter

(Process)

Connector

98 Flowcharting Concepts and Algorithms

Data Couple and Control Couple

Data couple carries data between two modules and it can have

upward or downward direction. But control couple only carries

information about data couple and does not carry any data. Control

couple is always directed upwards because it shows the module

which is to be evoked. Figure 1.56 show the two different

types of couple. The arrows with a blank circle at the tail is called

data couple. The arrow with a completely filled circle at the tail

end is called a control couple.

Figure 1.56 Couple (data and control)

How to Draw Structure Chart ?

In order to draw a structure chart, you will need to identify the

inputs, process and the outputs. You should draw different modules

for different processes in a system. This will be more clear

with the help of the example given below.

Example 1.20

Draw the structure chart for calculating the amount of scholarship

(a cut in the tuition fee) to be awarded to a student. The

conditions are as follows:

(a) If marks are 90, give 15% cut in the fee

(b) If marks are 85, and < 90, then give 12% cut in the fee

(Process)

B C

(Process)

Control

Couple

Data

Couple

Data

≥

Flowchart Techniques 99

Solution

The structure chart is shown in Figure 1.57.

Figure 1.57 Structure chart for example 1.20

Example 1.21

Draw a structure chart for searching a record as roll no. and then

print the record.

Solution

The structure chart for example 1.21 is shown in Figure 1.58. The

diagram is self-explanatory.

Looping in a Structure Chart

Looping means the repetitions of a set of statements in a

Scholar Ship

of Student

Validate Fee

Get Validated

Marks

Compute

Scholarship

Print Name of

Student get

Scholarship

Get Validated

Fee

Get Marks Get Validated

Marks

Compute

15% of Fee

Compute

12% of Fee

Get Fee

Fee

Marks

Valide

Flag

Fee

Valide

Flag

Marks

Flag

Valide

100 Flowcharting Concepts and Algorithms

program. In a structure chart, looping is shown by an angle with

the arrow mark. See Figure 1.59.

Figure 1.58 Structure chart for example 1.21

Conditional in Structure Chart

Conditional is a term which describes one action or operation

which takes place only when the condition is true and the other

action or operation which takes place when the condition is false.

Figure 1.59 gives the representation of the condition by a rectangular

polygon.

We have used the concepts of looping and conditional in

examples 1.20 and 1.21 as shown in Figure 1.57 and 1.58. (See

the angular arrows and the rectangular polygon).

1.14 Context Analysis Diagram

This type of diagram is made in the system analysis phase and it

gives a graphic representation of the system as a whole. In this

Search the

Record

Get Valid Find

Record

Print the

Record

Validated

RollNo.

Get Student

RollNo.

RollNo. Valide

Flag

RollNo.

Valide

Flag

Student RollNo.

Flowchart Techniques 101

Figure 1.59 Looping and conditional in structure chart

diagram entire system is shown as a single process. This diagram

identifies the external entities, the inputs and the outputs.

1.15 System Manual

The system manual is a statement of requirements which defines

specifically what is to be accomplished by the proposed computer

system. It is a fairly detailed document. Most of the data needed

for it is collected in the feasibility study. The document serves

both as a summary of the proposed system for internal purposes

and as a statement used in inviting equipment proposals from

vendors of data processing equipment.

On the basis of a preliminary screening, four or five vendors

may be invited to submit proposals. Each vendor is provided

with a copy of the manual of specifications and the rules for submitting

proposals. These may be followed-up by interviews with

vendors to clarify any misunderstandings or uncertainties in the

specifications. When the proposals are ready, the manufacturer’s

representative is usually provided with an opportunity for a

Conditional

Looping

Input Process Output

102 Flowcharting Concepts and Algorithms

presentation to the study group. This group studies the manual

and decides the selection of equipment and the supplier.

1.16 Source Code

The source code is the language in which a program is written by

the programmer. Source code is translated into object code by

assemblers and compilers, or a line at a time by an interpreter. In

some cases, the source code may be automatically converted into

another dialect or language by a conversion program. The source

code is not executable by the computer directly. It must be converted

into machine language first.

1.16.1 Command File

The command file is a machine language program that can be

loaded and executed in the computer. For example in Microsoft

DOS operating system, the Command.Com is one such file which

is used to boot the computer. Command files have a suffix .COM.

These files are designed to work only in specific memory locations.

They contrast with .EXE files, which can be relocated anywhere

in memory.

1.17 Input/Output Report Formats

The reports that are generated for the management or for the

working of an organization should be different from the data format

which is entered at the input stage of the processing cycle.

Thus the system analysis shows the relationship between the

individual items on each output and the items available as inputs

to the system.

The output reports and input documents should be documented

in terms of data contents and approximate layout. It is

possible to work back from the output contents, through the

system, to the inputs required. This is done by determining which

output data items are derived by calculation or by logical deduction.

All other items can then be broken down into those which

require fresh input every time, as part of input transaction

documents, and those which can be stored on file because they

are historical or relatively static.

Flowchart Techniques 103

1.18 Data-item Dictionaries

Data-item dictionary is used to define data, including identifiers,

location, and format for storage characteristics. It holds the

name, type range of values, source, and authorization for access

of each data element in the organization’s files and databases. It

also indicates which application program what data, so that

whenever a change in a data structure is contemplated, a list of

the affected programs can be generated. The data dictionary may

be a stand-alone information system used for management and

documentation purposes, or it may be an integral part of database

management system where it is used to actually control its

operation. Data integrity and accuracy is better insured in the

latter case. The data-item dictionary will contain the following

type of information:

(a) What tables and columns are included in the present structure.

(b) The names of the current tables and columns.

and data type.

(d) Any restrictions on the value of certain columns.

(e) The meaning of any data fields that are not evident.

(f) The relationships between items of data.

1.19 Testing Results

In order to completely test the program logic, the test data must

test each logical function of the program. The test data selected

for testing a program should include:

(a) Normal data which will test the generally used program

paths.

(b) Unusual but valid data, which will test the program paths

used to handle exceptions. Such data might be encountered

occasionally in running the program.

of the program.

104 Flowcharting Concepts and Algorithms

If a program runs successfully with the test data and produces

correct results, it is normally released for use. However,

even at this stage errors may remain. There are certain errors in

complex systems that remain hidden for months and years

together.

1.20 Review Reports and Management Decisions/Orders

Once the computer run system has become operational, it will

need to be examined to see if it has met its objectives. For example,

the costs and benefits will be compared with the estimates

produced at the system inception. This particular activity is often

known as "Post Audit"

The new system will also need to be reviewed and maintained

periodically for the following reasons:

(a) To deal with unforeseen problems arising in operation. For

example, programs may need to be modified to deal with

unforeseen circumstances.

(b) To confirm that the planned objectives are being met and to

take action if they are not.

requirements of business.

The results of a systems review would be used in future systems

analysis assignments.

1.20.1 Management Decision/Orders

In the event of adverse remarks given by the post audit team in

the functioning of the new computer system, it may be necessary

for the management to take some bold decision or issue orders for

the change/review of the system. For example, if the system is not

able to cope with the load of the work for which it was originally

designed, then it may not be worthwhile to continue with the

automatic new system. Let us take the case of the system

designed for the school fee collection. The system may be required

to meet the immediate collection of the fee. But if the system does

not meet this need as the working of the software is not reliable

or there is some other inherent defect in the system created, then

it will be necessary for the management to look into the new system

and ask for the review or change of the earlier system.

Flowchart Techniques 105

Test Paper Based on Chapter 1

Time allowed : 3 hr

Max.Marks : 100

Answer all questions

Q 1. Answer the following

(a) What are the advantages and limitation of pseudocodes ?

(b) List the program preparation techniques that are often included

under the term ‘Structured Programming’.

Q 2. What is a Flowchart ? List the flowcharting rules.

Q 3. What are the advantages and limitations of flowcharts ?

Q 4. Differentiate between the following

(a) Pseudocode and Flowchart

(b) Compiler and Interpreter

(d) Testing and Debugging

Q 5. What do you understand by structured programming ? State the characteristics

of structured programs.

Q 6. Write short notes on the following

(a) Data flow diagram (DFD)

(b) Compiler

(d) Algorithm

Q 7. What is modular concept in programming ? Mention a few essential

requirements of modular programming.

Q 8. What are the two broad types of programming errors ? How are they

detected?

Q 9. What do you understand by documenting a program ? Why is it

necessary ?

Q 10. (a) What is meant by program maintenance ? How can proper program

design make it easier to maintain programs ?

(b) What are the different ways of debugging and testing a program ?

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