isblank() Function Example in C Programming

In this source code example, we will see how to use the isblank() function in C programming with an example.

isblank() Function Overview

The isblank() function determines if the given character is a blank character, which includes space (' ') or a horizontal tab ('\t').

Key Points: 

- Requires the inclusion of the <ctype.h> header. 

- The function accepts an int (typically a character) as its argument. 

- It returns a non-zero value (true) if the character is blank; otherwise, it gives back 0 (false).

Source Code Example

#include <stdio.h>
#include <ctype.h>

int main() {
    char ch;

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

    if (isblank(ch))
        printf("'%c' is a blank character.\n", ch);
        printf("'%c' is not a blank character.\n", ch);

    return 0;


Enter a character:
' ' is a blank character.


1. We begin by including the necessary header files: stdio.h for input/output functions and ctype.h for character functions.

2. Inside the main() function, we initialize a character variable named ch.

3. The user is prompted to enter a character.

4. The isblank() function is used to test if the provided character is a blank.

5. Depending on the function's result, the program prints a relevant message to the console.