isascii - test for a 7-bit US-ASCII character
The isascii() function shall test whether c is a 7-bit US-ASCII character code.
The isascii() function is defined on all integer values.
The isascii() function shall return non-zero if c is a 7-bit US-ASCII character code between 0 and octal 0177 inclusive; otherwise, it shall return 0.
No errors are defined.
The Base Definitions volume of IEEE Std 1003.1-2001, <ctype.h>
First released in Issue 1. Derived from Issue 1 of the SVID.