C Programming if, if..else and Nested if...else Statement

The if, if...else and nested if...else statement are used to make one-time decisions in C Programming, that is, to execute some code/s and ignore some code/s depending upon the test expression.

C if Statement

if (test expression) {
       statement/s to be executed if test expression is true;
}

The if statement checks whether the text expression inside parenthesis () is true or not. If the test expression is true, statement/s inside the body of if statement is executed but if test is false, statement/s inside body of if is ignored.

Flowchart of if statement

Example 1: C if statement

Write a C program to print the number entered by user only if the number entered is negative.

#include <stdio.h>
      int main(){
      int num;
      printf("Enter a number to check.\n");
      scanf("%d",&num);
      if(num<0) {      /* checking whether number is less than 0 or not. */ 
            printf("Number = %d\n",num); 
      }  
/*If test condition is true, statement above will be executed, otherwise it will not be executed */
      printf("The if statement in C programming is easy.");
return 0;
}