isdigit - test for a decimal digit
int isdigit(int c);
[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to the ISO C standard.
The isdigit() function shall test whether c is a character of class digit in the program's current locale; see the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 7, Locale.
The c argument is an int, the value of which the application shall ensure is a character representable as an unsigned char or equal to the value of the macro EOF. If the argument has any other value, the behavior is undefined.
The isdigit() function shall return non-zero if c is a decimal digit; otherwise, it shall return 0.
No errors are defined.
To ensure applications portability, especially across natural languages, only this function and those listed in the SEE ALSO section should be used for character classification.
isalnum(), isalpha(), iscntrl(), isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(), isxdigit(), the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 7, Locale, <ctype.h>
First released in Issue 1. Derived from Issue 1 of the SVID.
The DESCRIPTION is updated to avoid use of the term "must" for application requirements.