C language isalpha() function: determine whether a character is an English letter

Function name : isalpha

Header file : <ctype.h>

Function prototype : int isalpha(int ch);

Function : Determine whether the character is an English letter

Parameters : int ch character to be checked

Return value : If ch is not an English letter, return 0; if ch is an English letter, return non-0

Program example : Determine whether the entered characters are English letters

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

Running results:

 inputacharacter:ffisalpha.