Functions

Character classification routines
These functions perform character classification. They return true or false status depending whether the character passed to the function falls into the function's classification (i.e. isdigit() returns true if its argument is any value '0' though '9', inclusive). If the input is not an unsigned char value, all of this function return false.

int isalnum (int __c)
int isalpha (int __c)
int isascii (int __c)
int isblank (int __c)
int iscntrl (int __c)
int isdigit (int __c)
int isgraph (int __c)
int islower (int __c)
int isprint (int __c)
int ispunct (int __c)
int isspace (int __c)
int isupper (int __c)
int isxdigit (int __c)

Character convertion routines
This realization permits all possible values of integer argument. The toascii() function clears all highest bits. The tolower() and toupper() functions return an input argument as is, if it is not an unsigned char value.

int toascii (int __c)
int tolower (int __c)
int toupper (int __c)