C++ isblank function explanation with example

C++ isblank() function:

isblank() function is used to check if a character is blank or not. It is defined in cctype header.

In this post, we will learn how isblank() works with examples.

Definition of isblank:

isblank function checks for a white-space character. A white-space character can be :

  • ’ ’ or space
  • ‘\t’ or horizontal tab
  • ‘\v’ or vertical tab
  • ‘\n’ or newline
  • ‘\f’ or feed
  • ‘\r’ or carriage return

It is defined in header and defined as:

int isblank(int c);

It takes the character to check c as the parameter, casted to an integer. It returns an integer value. If it is non-zero, it is a blank character, i.e. true. Else, it returns 0.


Let’s try to use isblank to count the number of blank spaces in a string. For example:

#include <iostream>
#include <cctype>

using namespace std;

int main()
    char str[100];
    int count = 0;
    int i = 0;

    cout << "Enter a string :" << endl;
    cin.get(str, 100);

        if (isspace(str[i]))
    } while (str[i] != '\0');

    cout << "Total number of blank found :  " << count << endl;


  • We are calculating the total number of blanks in a user given string.
  • str is used to store the user input string.
  • isspace is used to check if a character is blank or not. If yes, we are incrementing the value of count.
  • Finally, it is printing the value of count i.e. total blanks found.

It will print output as like below:

Enter a string :
hello world !!
Total number of blank found :  2

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