if..else..if Statement In C

An if statement can be followed by an optional else if...else statement, which is very useful to test various conditions using single if...else if statement.

When using if...else if..else statements, there are few points to keep in mind −

• An if can have zero or one else's and it must come after any else if's.
• An if can have zero to many else if's and they must come before the else.
• Once an else if succeeds, none of the remaining else if's or else's will be tested.

Syntax

The syntax of an if...else if...else statement in C programming language is −

if(boolean_expression 1) {
   /* Executes when the boolean expression 1 is true */
} else if( boolean_expression 2) {
   /* Executes when the boolean expression 2 is true */
} else if( boolean_expression 3) {
   /* Executes when the boolean expression 3 is true */
} else {
   /* executes when the none of the above condition is true */
}

Example:

#include <stdio.h>

int main() {

 int n1, n2, n3;

 printf("Enter three numbers: ");
 scanf("%d %d %d", &n1, &n2, &n3);

 // if n1 is greater than both n2 and n3, n1 is the largest
 if (n1 >= n2 && n1 >= n3)
 printf("%d is the largest number.", n1);

 // if n2 is greater than both n1 and n3, n2 is the largest
 else if (n2 >= n1 && n2 >= n3)
 printf("%d is the largest number.", n2);

 // if both above conditions are false, n3 is the largest
 else
 printf("%d is the largest number.", n3);

 return 0;
}

OUTPUT:

Enter three numbers: 5 15 10
15 is the largest number.