Boolean Type (Using the GNU Compiler Collection (GCC))

#### 6.12.11 Support for the `_Bool` Type ¶

The C99 standard added `_Bool` as a C language keyword naming the boolean type. As an extension, GNU C also recognizes `_Bool` in C90 mode as well as with `-std=c99` and later.

C23 added `bool` as the preferred name of the boolean type, but `_Bool` also remains a standard keyword in the language and is supported as such by GCC with `-std=c23`.

GNU C++ does not support `_Bool` as a keyword, but including `<stdbool.h>` defines it as a macro in terms of standard C++’s `bool` type.