 C Program Learning Part-7 - Engineer Simple

# DECISION MAKING AND LOOPING

### Looping:

In looping a sequence of statements are executed until some conditions for termination of the loop are satisfied. A program loop consists of two segments, one known as the body of the loop and the other known as the control statement. The control statement tests the certain conditions and then directs the repeated execution of the statements contained in the body of the loop.

Entry Controlled Loop:
In the entry controlled loop, the control conditions are tested before the start of the loop execution. If the conditions are not satisfied then the body of the loop will not be executed.

In the case of exit controlled loop, the test is performed at the end of the body of the loop and therefore the body is executed unconditionally for the first time.

When we know in advance exactly how many times the loop will be executed, we use a counter controlled loop. We use a control variable known as counter. The counter must be initialized, tested and updated properly for the desired loop operations. Sentinel Loops: In a sentinel controlled loop, a special value called a sentinel value is used to change the loop control from true to false. For example when reading data we may indicate the “ end of data” by a special value, like -1 and 999. The control variable is called sentinel variable. A sentinel controlled loop is often called indefinite repetition loop because the number of repetitions is not known before the loop begins executing.

### THE WHILE STATEMENT:

The basic format of the while statement is:

sum = 0;

n = 1;

while ( n <=10)

{

sum = sum + n * n;

n = n + 1;

}

printf(“sum = %d”, sum);

### Write a program to evaluate the equation: y =xn .

#include<stdio.h>

main()

{

int count, n;

float x,y;

printf(“Enter the values of x and n.\n”);

scanf(“%f %d”, &x, &n);

y = 1.0;

count = 1;

while( count <= n);

{

y = y * n;

count++;

}

printf(“x = %f; n= %d; x to power n = %f”, x,n,y);

}

#### THE DO STATEMENT:

The basic format of do statement is:

do

{

body of the loop

}

while(test condition);

### do....while Example

#define colmax 10

#define rowmax 12

main()

{

int row, column, y;

row = 1;

printf(" MULTIPLICATION TABLE\n");

printf("-----------------------------------------------\n");

do

{

column = 1;

do

{

y= row * column;

printf("%4d",y);

column = column +1;

}

while(column <= colmax);

{

printf("\n");

row = row + 1;

}

}

while(row <= rowmax);

printf("--------------------------------------------");

}

### THE FOR STATEMENT

The basic format of for statement is :

for( initialization; test condition; increment)

{

body of the loop;

}

For loop example:

main()

{

int sum;

for(n=1; n<=10; i++)

{

sum = sum + n;

}

printf(“Sum = %d”, sum);

}

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