Control statements - nested if statement

 Syntax for Nested If:

if  (condition) {

     if  (Nested if's Condition) {

              <True Block>

     } else {

                 <False Block>

      }

} else {

    

     if  (Nested if's Condition) {

              <True Block>

     } else {

                 <False Block>

      }

}

If statement or if-else statement present inside another if or else block(as shown above) is called nested if statements.

Example C program using nested-if statement:

 
  #include <stdio.h>
  int main() {
        int num1, num2, num3;
        printf("Enter 3 numbers:");
        scanf("%d%d%d", &num1, &num2, &num3);
        if (num1 > num2) {  // expression for if statement
                if (num1 > num3) {   // nested if -> if statement inside another if block
                        printf("%d is greatest\n", num1);
                } else {
                        printf("%d is greatest\n", num3);
                }
        } else {
                if (num2 > num3) {  // nested if -> if statement inside another else block
                        printf("%d is greatest\n", num2);
                } else {
                        printf("%d is greatest\n", num3);
                }
        }
        return 0;
  }

  Output:

  jp@jp-VirtualBox:~/$ ./a.out
  Enter 3 numbers:10 20 30
  30 is greatest