isdigit Function

Test for a decimal digit.

Include

<ctype.h>

Prototype

int isdigit(int c);

Argument

c

The character to test.

Return Value

Returns a non-zero integer value if the character, c, is a digit; otherwise, returns zero.

Remarks

A character is considered to be a digit character if it is in the range of ‘0’-‘9’.

Example

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

int main(void)
{
  int ch;

  ch = '3';
  if (isdigit(ch))
    printf("3 is a digit\n");
  else
    printf("3 is NOT a digit\n");

  ch = '#';
  if (isdigit(ch))
    printf("# is a digit\n");
  else
    printf("# is NOT a digit\n");
}

Example Output

3 is a digit
# is NOT a digit