isdigit function checks whether a character is decimal digit character or not.
Set of decimal digit(numeric) characters : 0 1 2 3 4 5 6 7 8 9.
Function prototype of isdigit
int isdigit(int c);
Function isdigit takes a character as input in form of an integer. When we pass a value of type char to isdigit function, corresponding ASCII value of that character is passed.
Return value of isdigit
If passed character is a decimal digit character, then isdigit function returns non-zero integer otherwise 0.
C program using isdigit function
The following program is to check whether a character is decimal digit character or not.
#include <stdio.h>
#include <ctype.h>
int main(){
char string[] = "1a. A";
int index = 0;
while(string[index] != '\0'){
if(isdigit(string[index])){
printf("'%c' is a digit\n", string[index]);
} else {
printf("'%c' is not a digit\n", string[index]);
}
index++;
}
return 0;
}
Output
'1' is a digit 'a' is not a digit '.' is not a digit ' ' is not a digit 'A' is not a digit