4.2.2. The While loop, Chapter - 4, Control Structures, HSSC-II (12th Class) Computer Science Key Point Notes

12th Class (HSSC-II) Computer SLO Based Key Point Notes

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Unit 4: Control Structure

4.2.2. The While loop:

• While loop is used to execute one or more statements repeatedly as long as the given condition remains TRUE.
• It is useful when the number of repetitions or iterations is not known in advance.
• It is the simplest loop of C.

Syntax:

Where:

Condition: The condition is given as a relational expression that controls the repetition of a loop. If the condition is TRUE, the body of the loop is executed. If the condition is FALSE, the body of the loop is not executed.

Loop Body: It consists of the statements that are to be executed repeatedly as long as the given condition is TRUE.

Working of while Loop

“while loop” is executed as follows:

1. First, the condition is evaluated.
2. If the condition is TURE, the body of the loop is executed. After executing the body, the control goes back to evaluate the condition.
3. Step 1 and step 2 will be repeated until the condition becomes FALSE. When the condition is FALSE, the loop is terminated or exited.

Flow chart of “while loop”

Example 1:

Write a program that displays “Pakistan” five times using a while loop.

#include <iosteam.h>
#include <conio.h>
void main()
{
        clrscr();
        int n = 1;
        while (n<=5)
        {
                cout<<“\n Pakistan”;
                n++;
        }
        getch();
}

Example 2:

Write a program that prints the sum of all the positive numbers up to 15 using a while loop.

#include <iostream.h>
#include <conio.h>
void main()
{
        clrscr();
        int k=1, sum=0;
        while(k<=15)
        {
                sum = sum + k;
                k++;
        }
        cout<<“Sum = “<<sum<<endl;
        getch();
}

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4.1. Control Structure

4-1-1 The if statement

4.1.3. The else-if Statement:

4.1.4. The Switch Statement:

4.1.5. Differentiate between ELSE- IF and SWITCH

4.2. Loop

4.2.1. The for Loop

4.2.2. The While loop:

4.2.3. The do-while loop

4.2.4. Differentiate between while and do-while loop

4.2.5. The break and Continue Statement

4.2.6 Exit() Function

4.2.7. Nested Loop

Chapter 4 (Complete Key Point Notes)

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