isgraphunsigned

isgraphunsigned is a term that appears in some programming contexts as a nonstandard or vendor-specific function or macro intended to test whether a character is graphical, with an emphasis on treating input as unsigned. It is not part of the ISO C standard library, and its exact availability and behavior can vary between environments. In practice, isgraphunsigned is typically described as an unsigned-safe variant of the standard isgraph family of functions.

In terms of signature, platforms that provide isgraphunsigned commonly declare it as an int isgraphunsigned(int ch); or as a macro with a similar interface. Like the standard ctype functions, its argument is expected to be an integer value representing a character code, typically in the range of unsigned char values (0 to 255) or EOF. The function returns a nonzero value if the input corresponds to a graphical character and zero otherwise. A graphical character is any printable character that has a visible representation, excluding white space.

Portability and usage considerations are important. Because isgraphunsigned is not standardized, its exact behavior, locale dependence, and availability can differ. When writing portable code, programmers often rely on the standard isgraph, invoked with an unsigned cast to avoid signed-ness issues, e.g., isgraph((unsigned char)ch). If a codebase uses isgraphunsigned, it should be documented that the function is nonstandard and guarded with platform checks or replaced with a portable alternative where necessary.

Related functions in the ctype family include isgraph, isprint, and isspace, which offer complementary checks for character properties.