Provided by: libsdl3-doc_3.2.8+ds-1_all 

NAME
SDL_isalpha - Query if a character is alphabetic (a letter).
HEADER FILE
Defined in SDL3/SDL_stdinc.h
SYNOPSIS
#include "SDL3/SDL.h" int SDL_isalpha(int x);
DESCRIPTION
WARNING : Regardless of system locale, this will only treat ASCII values for English 'a-z' and 'A-Z' as true.
FUNCTION PARAMETERS
x character value to check.
RETURN VALUE
Returns non-zero if x falls within the character class, zero otherwise.
THREAD SAFETY
It is safe to call this function from any thread.
AVAILABILITY
This function is available since SDL 3.2.0. Simple Directmedia Layer SDL 3.2.8 SDL_isalpha(3)