High resolution ("real-time") timers

To compile: gcc -lrt time.c
More info: link

C/C++ Show macros

In gcc or g++, to show all of the macros that are defined for a given platform:

gcc -dM -E test.c

or

g++ -dM -E test.cpp

C - Static Keyword

Usage	Effect
inside a function	remains even after the function call is long gone
modify a global variable	private to a certain file
modify a function	making those functions visible only to the file itself