putcharunsigned

Putcharunsigned is a non-standard C library function concept used in some codebases to output a single character to standard output, explicitly treating the input as an unsigned value. It is not defined by the C standard library, and its availability varies by platform and implementation.

Definition and behavior

In implementations that provide it, putcharunsigned is typically declared as int putcharunsigned(unsigned int c) or int putcharunsigned(unsigned char c). The function writes the character corresponding to the least-significant 8 bits of the argument to stdout. It returns the printed character promoted to int on success, or EOF on error. The emphasis of the name is on unsigned interpretation, which can be relevant when dealing with values that would be negative if treated as signed.

Rationale

Some environments use signed char by default, which can lead to sign-extended or negative values being propagated in character output routines. putcharunsigned aims to make the unsigned nature of the input explicit and predictable, providing a wrapper that masks to 8 bits and outputs the result as an unsigned value.

Relation to standard functions

Putcharunsigned is analogous in purpose to putchar and fputc, but with a focus on unsigned input. Because it is non-standard, recommended practice for portable code is to rely on the standard interfaces (such as putchar, fputc, or an explicit cast to unsigned char) rather than assuming putcharunsigned exists in the environment.

Portability and usage notes

If your project depends on putcharunsigned, you should document its presence and provide fallbacks for non-supporting platforms. For portable code, consider using putchar((int) (unsigned char) c) or fputc((unsigned char) c, stdout) to achieve the same unsigned-output behavior.

See also

putchar, putc, fputc, putchar_unlocked.