Decision making in C involves controlling the flow of a program based on certain conditions or criteria. This control flow allows the program to execute different sets of instructions or take specific actions based on the evaluation of conditions.

Decision Making can occur in these forms:

• if statement

• switch statement

• conditional operator statement (? : operator)

• goto statement

 

 

if statement:


The if statement may be implemented in different forms depending on the complexity of conditions to be tested. The different forms are,

1. Simple if statement

2. if. else statement

3. Nested if. else statement

4. Using else if statement

 


Example:

The marks obtained by a student in 5 different subjects are input through the keyboard. The student gets a division as per the following rules:

 

Percentage above or equal to 60 - First division

Percentage between 50 and 59 - Second division

Percentage between 40 and 49 - Third division

Percentage less than 40 - Fail

 

A program to calculate the division obtained by the student using if else is as follows:

 


# include <stdio.h>

void main( )

{

 

int m1, m2, m3, m4, m5, per ;       //declaring variables

printf ( "Enter marks in five subjects " ) ;

scanf ( "%d %d %d %d %d", &m1, &m2, &m3, &m4, &m5 ) ;      //input

per = ( m1 + m2 + m3 + m4 + m5 ) * 100 / 500 ;

if ( per >= 60 )

printf ( "First division\n" ) ;

else

{

if ( per >= 50 )

printf ( "Second division\n" ) ;

else

{

if ( per >= 40 )

printf ( "Third division\n" ) ;

else

printf ( "Fail\n" ) ;

}

}

}

 

 


Switch Statement:


the ‘switch’ statement is a control flow statement that allows a program to evaluate the value of a variable or expression and execute code blocks based on different possible values of that variable or expression.

 

Here is a code to clear the concept-


#include<stdio.h>

int main()

{

int i=2;

 switch (i)

{

    case 1:

    printf("Case1 ");

    break;

 

case 2:

    printf("Case2 ");

    break;

 

case 3:

    printf("Case3 ");

    break;

 

case 4:

    printf("Case4 ");

    break;

 

default:

    printf("Default ");

}

return 0;

}

 

 

Output:

Case 2