4.2.3. The do-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 Structures

4.2.3. The do-while loop

• The do-while loop is used to execute one or more statements repeatedly as long as the given condition is TRUE.
• It is similar to a “while loop” but in the do-while loop, the body of the loop comes before the condition.
• In a do-while loop, the body of the loop executes at least once even if the given condition is FALSE.

Syntax:

do
{
        statement 1;
        …………
        …………
}
while ( condition );

Working of do-while Loop

1. The block of statements following the keyword do is executed.
2. The condition at the end of the loop is evaluated. If the condition is true, control is transferred back to the beginning of the loop.
3. The loop is executed once again and then the condition is also checked again. This process continues till the condition becomes false.
4. When the condition becomes false, control is transferred to the next statement.
5. If the body of the loop consists of a single statement then braces are not required.

Flow chart of “do-while” loop

Example # 1:

Write a program that displays the first five numbers with their cubes.

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

Example # 2:

Write a program that reads the current state of a telephone line. The user should enter ‘w’ for working and ‘d’ for dead. Any other input will be invalid.

#include <iostream.h>
#include <conio.h>
void main()
{
        clrscr();
        char ch;
        do
        {
                cout<<“ \n Enter the state of phone: w for working and d for dead: “;
                ch = getche();
        }
        while ( ch != ‘w’ && ch != ‘d’);
        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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