C Program to Check if a Number Is Positive Or Negative

Methods to Check Number Sign

Given an integer input, the objective is to check whether the given integer is Positive or Negative. In order to do so we have the following methods:

• Method 1: Using Brute Force

  Algorithm 1

  For a user input num:

  If the num > 0: it is a positive number.

  If the num < 0: it is a negative number.

  Else the number has to be zero itself

  Same logic we have followed in the below C program.

  #include <stdio.h>
  int main() {
      int num;
      printf("Enter a number: ");
      scanf("%d", &num);
      if (num > 0) {
          printf("The number is Positive\n");
      } else if (num < 0) {
          printf("The number is Negative\n");
      } else {
          printf("The number is Zero\n");
      }
      return 0;
  }

  Output:

  Enter a number: -5
  The number is Negative

• Method 2: Using Nested if-else Statements

  Algorithm 2

  1. Take input from the user.

  2. If the number is greater than zero, print "Positive".

  3. Else, check if the number is less than zero.

  4. If true, print "Negative".

  5. Otherwise, print "Zero".

  #include <stdio.h>
  int main() {
      int num;
      printf("Enter a number: ");
      scanf("%d", &num);
      if (num >= 0) {
          if (num == 0)
              printf("The number is Zero\n");
          else
              printf("The number is Positive\n");
      } else {
          printf("The number is Negative\n");
      }
      return 0;
  }

  Output:

  Enter a number: -8
  The number is Negative

• Method 3: Using the ternary operator

  Algorithm 3

  1. Take input from the user.

  2. Use the ternary operator to check if the number is positive, negative, or zero.

  3. Print the result accordingly.

  #include <stdio.h>
  int main() {
      int num;
      printf("Enter a number: ");
      scanf("%d", &num);
      (num > 0) ? printf("The number is Positive\n") : 
      (num < 0) ? printf("The number is Negative\n") : 
                  printf("The number is Zero\n");
      return 0;
  }

  Output:

  Enter a number: 0
  The number is Zero