C Tutorial/ctype.h/isalnum
isalnum
Item Value Header file ctype.h Declaration int isalnum(int ch); Return returns nonzero if its argument is either a letter of the alphabet or a digit. returns zero if the character is not alphanumeric.
#include <ctype.h>
#include <stdio.h>
int main(void)
{
char ch;
printf(". to exit:");
for(;;) {
ch = getc(stdin);
if(ch == ".")
break;
if(isalnum(ch))
printf("%c is alphanumeric\n", ch);
}
return 0;
}