chisdigit

Chisdigit is a function name used in various programming libraries to check whether a given character represents a decimal digit. It is conceptually equivalent to testing whether the input character is one of the ten ASCII digits '0' through '9', though some implementations may be locale-aware and recognize other digit characters in other scripts.

Typical usage is to pass a character or its integer code to chisdigit; the function returns a boolean value or an integer flag (commonly true/false or 1/0) indicating digit status. In C-like environments, the input must be representable as an unsigned char and the result may be affected by the active C locale via setlocale.

From a portability perspective, many projects rely on the standard isdigit function from ctype.h rather than chisdigit, because isdigit is part of the C standard and well-documented. Some codebases implement chisdigit as a wrapper around isdigit to provide a uniform API across languages or to enforce unsigned-char input.

Related concepts include the isdigit family (isxdigit, isalpha) and, in higher-level languages, methods like String.isdigit (Python) or Character.isDigit (Java).

History and naming: chisdigit is not a universally standardized function name; it appears in some libraries, educational materials, or custom utility modules. The exact signature and behavior can vary by language and library.