isdigit() ctype Macro (ctype.h) isdigit() Check if a character is a numeral #include <ctype.h> int isdigit(c) int c; isdigit tests whether the argument c is a numeral (0-9). It returns a number other than zero if c is a numeral, and zero if it is not. isdigit assumes that c is an ASCII character or EOF. ***** Example ***** For an example of how to use this macro, see the entry for ctype. ***** See Also ***** ASCII, ctype COHERENT Lexicon Page 1