02 iec t1_s1_plt_session_02

Installing Windows XP Professional Using Attended Installation

Slide 1 of 35Session 2Ver. 1.0

Programming Logic and Techniques

In this session, you will learn to:Identify variables and constants

Use data types

Use operators

Represent decisions in a flowchart

Objectives




Example:Flowchart to display the sum of two numbers

Variables and Constants

Start

Stop

Accept theSecond Number

Add the two Numbersand Store the Result

Display the Result

Accept theFirst Number




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.

10 15 25

nNum1 nNum2 nSum

Variables

Constants





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

Start

Stop

Accept nNum2

nSum = nNum1 + nNum2

Display nSum

Accept nNum1





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




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”

Just a minute

Answer:Constants: 21, “10, Kingsway Camp”, “Henri”, “185”

Variables: Age, Address, Name




Numeric variables can contain only numbers.

These variables can be used in arithmetic operations.

Numeric




Character variables can contain any combination of letters, numbers, and special characters.

These variables cannot be used for calculation.

Character




Declaring Variables

Start

Stop

Accept nNum2

nSum = nNum1 + nNum2

Display nSum

Accept nNum1

numeric nNum1,nNum2, nSum

Declaration of Variables

Example:




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.

Variable Naming Conventions




Operators are symbols for some predefined operations.

The operators that are used in flowcharts are:Arithmetic operators

Relational operators

Logical operators

Using Operators




Arithmetic operators are used to perform arithmetic calculations.

The symbols that represent arithmetic operations are called arithmetic operators (*, /, +, -, %).

Arithmetic 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 (=,>,<,!=,>=,<=).

Relational 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.

Logical Operators




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

Stop

Accept nPrice

Accept nQuantity

Display cItemName, nValue

Accept cItemName

character cltemNamenumeric nPrice, nQuantity, nValue

nValue = nPrice * nQuantity




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.

Representing Decisions in a Flowchart

Is nNum1 = nNum2 ?

Yes

No

Display “The numbers are

equal”

Display “The numbers are

not equal”




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

Representing Decisions in a Flowchart (Contd.)

Start

Accept nNum2

Accept nNum1

numeric nNum1,nNum2

A




Example (Contd.):


A

Is nNum1=nNum2?

Is nNum1>nNum2?

Stop

Display nNum2

Display nNum1

Display “ The numbers are equal”

Yes

Yes

No

No




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


Start

Stop

Display nX

Accept nX

numeric nX

IsnX>10 AND nX%2=0?

No

Yes




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

Accept nYear

numeric nYear

A

Display “Please enter a year”




Flowchart to determine a leap year (Contd.)


A

Is nYear % 4=0 AND (nYear % 100 !=0 OR nYear % 400=0) ?

Stop

Display “This is a leap year”

Display “This is not a leap year”

No

Yes




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

Stop

Accept cTypeAccept nScreen

numeric nScreen, nDiscountcharacter cType

IscType=‘B’?

Yes

No

IscType=‘C’?

IsnScreen=21?

IsnScreen=14?

nDiscount=5% of SP

nDiscount=8% of SP

nDiscount=10% of SP

Yes

No No

No

Yes

Yes




Exercises




Study the given flowchart and answer the following questions.

What will be the output when:nNum=7

nNum=3

nNum=11

Exercise 1

Is nNum>10?

Is nNum>5?

Stop

Display “REJECT”

Display “OK”

Display “ GOOD”Yes

Yes

No

No

Start

Accept nNum

numeric nNum




Study the flowchart and answer the following questions.

Exercise 2

Is nX > nY ?

Is nY > 100 ?

Stop

Display nY

Display “ GOOD”Yes

No

No

Yes

Start

Accept nX

numeric nX, nY

Accept nY

Is nX > 100 ?

Yes

No




Exercise 2 (Contd.)

What will be the output when:nX=150 and nY=75

nX=90 and nY=50

nX=40 and nY=80




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

Exercise 3




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

Exercise 4




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.

Exercise 5




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




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.

Summary (Contd.)

02 iec t1_s1_plt_session_02

Technology

attended installationvariables

attended installationjust

nnum2 nnum2

constants contd

nnum1 nnum2 nsumvariables

flowchart contd

calledarithmetic operators

nnum2 display nsumstop