C not Cpp, nor C++
Modified 2025-09-24
External Variables
The external variables can only be defined once, outside of any
function. The external variables must be defined with extern in each
function which needs these variables. Usually the extern
declarations are collected in a header file, and then the extern
definitions prepare them for usage in the functions.
Preprocessor
__FILE__, __func__ and __LINE__ are useful to report errors to devs.
There's so many directives I haven't heard before: #error#, multiline
#define's, ## (concatenation), ...