ABL electronic PIC Microcontrollers PIC16 - Manual (Page 289)

mikroC provides a set of standard ANSI C library functions for testing and map-
ping characters.
Note: Not all of the standard functions have been included. Functions have been
implemented according to the ANSI C standard, but certain functions have been
modified in order to facilitate PIC programming.
isalnum
isalpha
iscntrl
isdigit
isgraph
islower
isprint
ispunct
isspace
isupper
isxdigit
toupper
tolower
MikroElektronika: Development tools - Books - Compilers
281
page
mikroC - C Compiler for Microchip PIC microcontrollers
mikroC
making it simple...
ANSI C Ctype Library
Library Routines
Prototype char isalnum(char character);
Description Function returns 1 if the
character
is alphanumeric (A-Z, a-z, 0-9), otherwise returns
zero.
isalnum