We use the **`isblank()`** function in C++  to determine if a given character is a blank character. A blank character is any of the following characters:
* `' '`: The space character.
* `'\t'`: The tab character.

# Library
To use the `isblank()` function, include the following library:
```C
#include <cctype>
```

# Declaration
The `isblank()` function is declared as follows:
```C
int isblank(int c);
```
* `c`: The ASCII value of the character being checked.

>Note: If `c` is not an `unsigned char` or `EOF`, the behavior of the `isblank()` function is undefined.

# Return value
* The `isblank()` function returns a non-zero value if `c` is a blank.
* The `isblank()` function returns `0` if `c` is not a blank.

# Code
## Example 1
Consider the code snippet below, which demonstrates the use of the `isblank()` function.



#include <cctype>
#include <iostream>
using namespace std;

int main()
{
  char c1 = 'a';
  char c2 = ' ';  

  cout<<"'"<<c1<<"' is blank: "<<isblank(c1)<<endl;
  cout<<"'"<<c2<<"' is blank: "<<isblank(c2)<<endl;
  
  return 0;
}

## Explanation

Two characters `c1` and `c2` are declared in *lines 7-8*. `c1` is not a blank and `c2` is a blank.

* *line 10*: We use the `isblank()` function in *line 10* to check whether `c1` is a blank. The `isblank()` function returns 0, which means that `c1` is not a blank.
* *line 11*: We use the `isblank()` function in *line 11* to check whether `c2` is a blank. The `isblank()` function returns a non-zero value, which means that `c2` is a blank.

## Code 2
Consider the code snippet below, which uses the `isblank()` function to remove the blanks from other characters in a string.



#include <cctype>
#include <cstring>
#include <iostream>
using namespace std;

int main()
{
  char str[] = "H el lo   w o r d!! ";
  int len = strlen(str);
  char withoutBlanks[len];
  int blankCount = 0;

  int ind = 0 ;
  for(int i = 0; i < len; i++){
    if( isblank(str[i])==0 ){
      withoutBlanks[ind] = str[i];
      ind++;
    }else{
      blankCount++;
    }
  }
  withoutBlanks[ind] = '\0';
  
  cout<<"string = "<<str<<endl;
  cout<<"string without blanks = "<<withoutBlanks<<endl;
  cout<<"number of blanks in string = "<<blankCount<<endl;
  return 0;
}

## Explanation
* *line 8*: A string `str` is declared that contains both blank and non-blank characters.
* *line 10*: A string `withoutBlanks` is declared that will contain the non-blank characters of `str`.
* *line 11*: A variable
`blankCount` is declared that will contain the count of the number of blank characters of `str`.
* *lines 14-17*: Loop over the characters of `str` such that if a character is a non-blank, it is copied the character in `withoutBlanks`. If a character is a blank, add one to `blankCount`.

What is isblank() in C++?

The isblank() function determines if a character is blank (' ' or '\t'), returning non-zero if true and zero if false.