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In this tutorial, you will learn how to write a C program to check whether a given input is a digit or not by using if-else. Along with the program, we will also learn various examples, algorithms, and fully explained program.

Problem Statement

The program should take the input from the user. It should prompt the user to enter a character and determine whether the entered character is a digit or not.

For Example

Enter a character: 7

Output: The input is a digit.

Algorithm

1. Declare a variable input of type char to store the user input.
2. Display a prompt asking the user to enter a character.
3. Read the character entered by the user and store it in the input variable.
4. Use an if-else statement to check if input is between ‘0’ and ‘9’.
5. If the condition is true, print “The input is a digit.”
6. If the condition is false, print “The input is not a digit.”
7. Return 0 to indicate successful execution of the program.

Program to check a given input is digit or not

#include <stdio.h>
int main() {
    char input;

    printf("Enter a character: ");
    scanf("%c", &input);

    if (input >= '0' && input <= '9') {
        printf("The input is a digit.\n");
    } else {
        printf("The input is not a digit.\n");
    }
    return 0;
}

Output 1

Enter a character: aa
The input is not a digit

Output 2

Enter a character: 2
The input is a digit

Program Explanation

The program starts by declaring a variable input of type char to hold the user input. It then prompts the user to enter a character and reads the input using the scanf function. After taking the value from the user it will be stored in the input variable.

Next, the program uses an if-else statement of C to check if the input character is a digit. The condition input >= '0' && input <= '9' checks if the ASCII value of input falls within the range of ‘0’ to ‘9’. If the condition is true, it prints “The input is a digit.” Otherwise, it prints “The input is not a digit.”

Conclusion

This C program allows users to enter a character and check whether it is a digit or not using if-else statements. It provides a simple and straightforward way to determine the digit status of the input character.