03 iec t1_s1_plt_session_03

Installing WindowsLogic and Techniques
Programming XP Professional Using Attended Installation
Objectives

In this session, you will learn to:
Use the dry run table
Identify repetitive processes
Identify modular approach to programming

Ver. 1.0 Session 3 Slide 1 of 29

Using Dry Run

Helps you do a logic check
Understand the flow of control in a flowchart
Evaluate the output of the program with a set of sample
values
Provides a step by step evaluation of values in the variables
of the program


Using Dry Run (Contd.)

Example:
All candidates have to take three tests. A candidate is selected
for the interview round based on the scores of all the three
tests. The individual score in each test has to be greater than
75 and the average score across the three tests should be a
minimum of 80. The call letter for the interview is to be sent to
candidates who have been selected and a rejection letter is to
be sent to the rest. Represent the logic for the above process
by using a flowchart.



Flowchart to select a candidate
Start

Declare Variables

Accept Values and
Calculate nAverage

Is
nAverage>= 80 AND No Display “ Rejection
nTest1 > 75 AND letter to be sent”
nTest2 > 75 AND
nTest3 > 75 ?

Yes
Display “Interview
call letter to be sent”

Stop



Dry Run Table:

S.No. nTest1 nTest2 nTest 3 nAverage Output

1. 95 90 88 91 Interview call letter to be sent

2. 80 77 83 80 Interview call letter to be sent

3. 90 92 74 85.33 Rejection letter to be sent

4. 76 76 76 76 Rejection letter to be sent


Iteration

An important characteristic of a computer is its ability to
execute a series of instructions repeatedly.
A loop is a sequence of instructions that will be repeated
more than once.
A loop performs steps in a specified sequence.
There are two types of loops:
fixed loops where the number of repetitions is known
variable loops where the number of repetitions is not known


Iteration (Contd.)

Example:
Flowchart to display the sum of ten numbers
Start

numeric nNum,
nSum, nCounter

nCounter=0
nSum=0

Accept nNum

nSum=nSum+nNum

nCounter=nCounter+1

Yes Is No
nCounter<10 ? Display nSum

Stop


Iteration (Contd.)

Dry Run Table:

S. No. nNum nSum nCounter Output
0. - 0 0
1. 5 5 1
2. 12 17 2
3. 7 24 3
4. 6 30 4
5. 2 32 5
6. 10 42 6
7. 8 50 7
8. 3 53 8
9. 16 69 9
10. 4 73 10 73


Iteration (Contd.)

Example:
You have been assigned the responsibility of generating an
address list of all the people working in your office. For each
person, you will need to accept the name, address, and the
telephone number and print a list containing the collated
details.


Iteration (Contd.)

Flowchart segment to display employee details of 25 people

nCounter = 1

Is No
nCounter<=25?

Yes Stop
Accept cName

Accept cAddress

Accept cTelno

Display cName,
cAddress, cTelno

nCounter=nCounter+
1

Iteration (Contd.)

Example:
Let us look at the same example of preparing the test
performance report in the decision-making section again. Now,
apart from finding out whether a candidate has to be sent a call
letter or a rejection letter, we also have to calculate the number
of candidates who have been sent interview call letters and the
number of candidates who have been sent rejection letters,
using a flowchart.


Iteration (Contd.)

Flowchart to calculate the total number of call letters and rejection
letters sent
Start

Variable Declaration

Accept Values

Is
nAverage >=80 AND No
nTest1 > 75 AND nTotReject=nTotReject+1
nTest2 > 75 AND
nTest3 > 75 ?

Yes

nTotSelect=nTotSelect+1

Process
A B


Iteration (Contd.)

Flowchart to calculate the total number of call letters and rejection
letters sent (Contd.)

B
A

Display “Any more
candidates (Y/N)? ”

Accept cChoice

Is No
cChoice = “Y”?

Yes Display nTotSelect
Display nTotReject

Stop


Iteration (Contd.)

Dry Run Table:

S. No. nTest1 nTest2 nTest3 nAverage Output
1. 95 90 88 91 nTotSelect is incremented by 1.
2. 80 77 83 80 nTotSelect is incremented by 1.
3. 90 92 74 85.33 nTotReject is incremented by 1.
4. 76 76 76 76 nTotReject is incremented by 1.


Identifying Modular Approach to Programming

A program needs to be amended periodically to respond to
changing conditions or requirements.
This encouraged programmers to adopt a more disciplined
approach to program writing.
The techniques that were adopted are known as modular
or structured programming techniques.
Modular programming includes features that are designed
not only to solve the problem at hand but also to make the
logic clear to someone reading the program.


Identifying Modular Approach to Programming (Contd.)

Long, continuous programs can be broken up into a series
of individual modules that are related to each other in a
specified manner.

Main
Program

Module1 Module2 Module3



Example:
Flowchart to show modular programming
Start

numeric nNum1, Add
nNum2, nNum3, nSum

nSum=nNum1 + nNum2
Accept nNum1, + nNum3
nNum2, nNum3

Return
Add

Display nSum

Stop



Example:
Accept the test scores for 10 students and display their
individual averages. The scores of the students cannot be
negative.
The table shows the variables used in the flowchart.
Variable Data Type Variable Name

Student Name character cStudentName

Score of Test 1 numeric nTest1



Average of Test Scores numeric nAverage



Flowchart to calculate average marks of 10 students
Accept

Accept cStudentName

Accept Average
Accept nTest1

nAverage=(nTest1+nTest2
Average Accept nTest2 +nTest3) / 3

Accept nTest3 Return
Display cStudentName,
nAverage
Is
nTest1>=0 AND Yes
nTest2>=0 AND
nTest3>=0 ?

No Return

Display “Test score cannot
be less than zero”



Example:
The total expenditure on salaries for the month needs to be
calculated. As per company policy an employee receives a
minimum of $500. Depict the logic for automating the task by
using flowcharts.
The table shows the variables used in the flowchart.

Variable Data Type Variable Name

Employee code character cEmpCode

Employee salary numeric nSalary

Total salary numeric nTotSalary

Choice character cChoice



Flowchart to calculate total monthly expenditure on salaries

Accept

Is No Summation
cChoice = “Y” ? Accept nSalary

Yes
nTotSalary=nTotSalary+nSalary
Is Yes
Accept nSalary >=500 ?

Return Return
No
Summation Display ”Salary cannot
be less than $500”



Dry Run Table:

S. No. nSalary nTotSalary Output
1. - 0
2. 4500 4500
3. 5500 10000
4. 3400 13400
5. 5600 19000
6. 3000 22000
7. 5000 27000
8. 450 27000 Salary cannot be less than $500
9. 9000 36000
10. 8900 44900
11. 4500 49400 49400



Exercises


Exercise 1

Draw a flowchart to print the product of the first 10 even
numbers.


Exercise 2

Draw a flowchart to accept 50 numbers and also display the
total number of odd and even numbers.


Exercise 3

Draw a flowchart to display the highest of any 10 numbers
entered.


Exercise 4

Draw a flowchart that accepts input from a user and
displays the result, depending on whether the user wishes
to multiply or divide the numbers provided as input. The
Multiply module of the program can multiply maximum of
three numbers. The Divide module of the program should
check that the denominator should not be zero.


Summary

In this session, you learned that:
The concept of dry run will help you perform a logic check and
understand the flow of control in a flowchart.
A loop is a sequence of instructions that will be repeated more
than once.
A loop performs steps in a specified sequence.
There are two types of loops:
Fixed loops where the number of repetitions is known
Variable loops where the number of repetitions is not known


Summary (Contd.)

Statements within a loop will be executed repeatedly
until the condition becomes false.
The structured programming technique is a disciplined
approach to program writing.
A large program can be divided into several modules, where
each module performs a specific task. A module is also called
a procedure.
A procedure or a module is invoked from the main program
and the control is returned from the procedure to the main
program by using the return statement.


03 iec t1_s1_plt_session_03

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03 iec t1_s1_plt_session_03