02 iec t1_s1_plt_session_02

Installing WindowsLogic and Techniques
Programming XP Professional Using Attended Installation
Objectives

In this session, you will learn to:
Identify variables and constants
Use data types
Use operators
Represent decisions in a flowchart

Ver. 1.0 Session 2 Slide 1 of 35

Variables and Constants

Example:
Flowchart to display the sum of two numbers
Start

Accept the
First Number

Accept the
Second Number

Add the two Numbers
and Store the Result

Display the Result

Stop


Variables and Constants (Contd.)

The internal memory consists of different locations in which
data is stored.
A computer needs to identify the memory locations to be
able to retrieve values from or store values in them.
The value of a variable changes each time the set of
instructions is executed.



The values stored in the variables are known as constants.

Constants

10 15 25

nNum1 nNum2 nSum

Variables



Example:
Flowchart to display the sum of two numbers using variables
Start

Accept nNum1

Accept nNum2

nSum = nNum1 + nNum2

Display nSum

Stop


Just a minute

Each day, the courier service delivers some letters. The
number of letters is different each day. Regardless of the
number of letters delivered by the courier service, they are
paid a carrying charge of $5. Identify the variable and
constant data in this situation.
Variable:
Constant:

Answer:
Variable: Number of letters
Constant: Carrying charge $5


Just a minute

Identify the variables and constants from the following list:
1. Age
2. Address
3. 21
4. “10, Kingsway Camp”
5. “Henri”
6. Name
7. “185”

Answer:
Constants: 21, “10, Kingsway Camp”, “Henri”, “185”
Variables: Age, Address, Name


Numeric

Numeric variables can contain only numbers.
These variables can be used in arithmetic operations.


Character

Character variables can contain any combination of letters,
numbers, and special characters.
These variables cannot be used for calculation.


Declaring Variables

Example:
Start

numeric nNum1, Declaration
nNum2, nSum of Variables

Accept nNum1

Accept nNum2

nSum = nNum1 + nNum2

Display nSum

Stop


Variable Naming Conventions

The first letter of the variable may indicate the data type
used.
The variable name should clearly describe its purpose.
In case of multiple words, the first letter of each word could
be capitalized for better readability.


Using Operators

Operators are symbols for some predefined operations.
The operators that are used in flowcharts are:
Arithmetic operators
Relational operators
Logical operators


Arithmetic Operators

Arithmetic operators are used to perform arithmetic
calculations.
The symbols that represent arithmetic operations are called
arithmetic operators (*, /, +, -, %).


Relational Operators

Relational operators are used to test the relationship
between two variables or the relationship between a
variable and a constant.
There are six relational operators (=,>,<,!=,>=,<=).


Logical Operators

Logical operators (AND, OR, NOT) are used to combine
expressions containing relational operators:
nNum1 = 7 AND nNum2 > 5
nNum1 = 7 OR nNum2 > 5
NOT nNum2 <= 5
The order of precedence for the execution of logical
operators is NOT, AND, and OR.


Just a minute

Draw a flowchart to accept item name, price, and quantity.
You need to calculate the value as the product of price and
quantity, and display the calculated value and the item
name using variables.


Just a minute (Contd.)

Answer:
Start

character cltemName
numeric nPrice, nQuantity, nValue

Accept cItemName

Accept nPrice

Accept nQuantity

nValue = nPrice * nQuantity

Display cItemName, nValue

Stop


Representing Decisions in a Flowchart

Many problems require decisions to be made.
All decisions may or may not state an action to be taken if
the condition is false.
Following is a flowchart segment to compare two numbers
and check for equality.

Is nNum1 = No
nNum2 ?

Yes

Display “The Display “The
numbers are numbers are
equal” not equal”


Representing Decisions in a Flowchart (Contd.)

Example:
Accept two numbers and print the larger of the two numbers

Start

numeric nNum1,
nNum2

Accept nNum1

Accept nNum2

A



Example (Contd.):
A

Is Yes Display “ The
nNum1=nNum2?
numbers are equal”

No

Is Yes
nNum1>nNum2? Display nNum1

No

Display nNum2

Stop



Example:
Print the value of nX only if the value of nX is greater than 10
and nX is an even number
Start

numeric nX

Accept nX

Is
No
nX>10 AND
nX%2=0?

Yes

Display nX

Stop



Example:
Accept the year and then determine whether the year is a leap
year or not. A leap year is one that is divisible by 4, other than
a century year, such as 1900. A century year, which is divisible
by 400, such as 2000, is also a leap year.
To evaluate the given condition, we can interpret this as:
• If year is divisible by 4 AND not divisible by 100 OR divisible by
400, it is a leap year.



Flowchart to determine a leap year

Start

numeric nYear

Display “Please
enter a year”

Accept nYear

A



Flowchart to determine a leap year (Contd.)

A

Is
nYear % 4=0 AND
No Display “This is
(nYear % 100 !=0 OR
nYear % 400=0) ? not a leap year”

Yes

Display “This is
a leap year”

Stop



Example:
To decide about the discount percentage on a TV, the sales
person needs to check the type of TV. If the TV is Black and
White [B], the discount will be 5 percent of the selling price. If
the type of TV is colored[C], then he has to verify the size of
TV screen. For 14 inches screen, discount is 8 percent of the
selling price and for 21 inches screen, the discount is 10
percent of the selling price.



Flowchart to calculate discount
Start

numeric nScreen, nDiscount
character cType

Accept cType
Accept nScreen

Is Yes
cType=‘B’? nDiscount=5% of SP

No

Is Yes Is Yes
nDiscount=8% of SP
cType=‘C’? nScreen=14?

No No

Is Yes
nDiscount=10% of SP
nScreen=21?

No

Stop



Exercises


Exercise 1

Study the given flowchart and answer the following
questions.
Start
What will be the output when:
nNum=7 numeric nNum

nNum=3 Accept nNum
nNum=11
Is Yes
nNum>10? Display “ GOOD”

No

Is Yes
nNum>5? Display “OK”

No

Display “REJECT”

Stop


Exercise 2

Study the flowchart and answer the following questions.
Start

numeric nX, nY

Accept nX

Accept nY

Is Yes Is Yes
nX > 100 ? Display “ GOOD”
nX > nY ?

No No
Is No
nY > 100 ?

Yes
Display nY

Stop


Exercise 2 (Contd.)

What will be the output when:
nX=150 and nY=75
nX=90 and nY=50
nX=40 and nY=80


Exercise 3

Draw a flowchart to accept a number and then find out
whether or not the number is divisible by 5.


Exercise 4

Draw a flowchart to accept three numbers and display the
largest number.


Exercise 5

Candidates have to enter their age. The age cannot be
negative. If a negative age is entered, an error message
has to be displayed, otherwise the age is displayed.
Represent the error checking logic for this situation using a
flowchart.


Summary

In this session, you learned that:
Data can be categorized as a constant or variable.
Data types can be:
• Numeric
• Character
The operators are:
• Arithmetic
• Relational
• Logical
– Arithmetic operators are used to perform arithmetic
calculations. The symbols that represents arithmetic operations
are called arithmetic operators (*,/,+,-,%).


Summary (Contd.)

– Relational operators are used to test the relationship between
two variables. The symbols that represent relational operations
are called relational operators (<,>,=,!=).
– Logical operators (AND, OR, NOT) are used to combine
expressions containing relational operators.
– The decision box is used to apply conditions by asking a
question in a flowchart.


02 iec t1_s1_plt_session_02

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