C Library - isprint() function

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The C ctype library isprint() function checks whether the passed character is printable. A printable character is a character that is not a control character. Printable characters include all visible characters (letters, digits, punctuation marks, and symbols) as well as the space character.

This function declared in the <ctype.h> header.

Syntax

Following is the C library syntax of the isprint() function −

int isprint(int c);

Parameters

This function accepts a single parameter −

• c − This is the character to be checked, passed as an int. Although the parameter is of type int, it typically represents an unsigned char value or EOF.

Return Value

It returns Non-zero(True), if the character is a printable character and it returns Zero(False) if the character is not a printable character.

Example 1: Checking Alphanumeric and Space

This example checks if the characters 'A', space (' '), and tab ('\t') are printable. 'A' and space are printable, but tab is not.

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

int main() {
   char c1 = 'A';
   char c2 = ' ';
   char c3 = '\t';

   printf("isprint('%c'): %d\n", c1, isprint(c1));
   printf("isprint('%c'): %d\n", c2, isprint(c2));
   printf("isprint('%c'): %d\n", c3, isprint(c3));

   return 0;
}

Output

The above code produces following result −

isprint('A'): 16384
isprint(' '): 16384
isprint('	'): 0

Example 2: Checking Extended ASCII Character

This example checks extended ASCII characters. Some extended ASCII characters (e.g., 176 and 255) are printable, while others (e.g., 128) are not.

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

int main() {
   char c1 = 128; // Extended ASCII character
   char c2 = 176; // Extended ASCII character
   char c3 = 255; // Extended ASCII character

   printf("isprint('%c'): %d\n", c1, isprint(c1));
   printf("isprint('%c'): %d\n", c2, isprint(c2));
   printf("isprint('%c'): %d\n", c3, isprint(c3));

   return 0;
}

Output

After execution of above code, we get the following result

isprint('PAD'): 0
isprint(''): 1
isprint(''): 1