C language isalnum() function: determine whether a character is a letter or number

Function name : isalnum

Header file : <ctype.h>

Function prototype : int isalnum(int ch);

Function : Determine whether a character is a letter or number

Parameters : int ch character to be checked

Return value : Returns 0 if ch is not a letter or number, returns non-0 if ch is a letter or number

Program example : Determine whether the entered characters are letters or numbers

 #include<ctype.h>#include<stdio.h>intmain(){charch;printf(inputacharacter:);scanf(%c,&ch);if(isalnum(ch)){printf(%cisalnum.,ch) ;}else{printf(%cisnotalnum.,ch);}putchar('n');return0;}

Running results:

 inputacharacter:ffisalnum.