[VS2005] error C3861: 'exit': identifier not found

when I try to use some example codes of OpenGL, I'll sometimes get the compile error
"error C3861: 'exit': identifier not found" from the keyboard subroutine:

• void keyboard(unsigned char key, int x, int y){
• switch(key){
• case 27:
• exit(0);
• break;
• }
• }

Finally, I found the solution that is to add the include information on the top of the cpp file.

#include < stdlib.h >

The original discussion thread is from Windows Forums, and solution is provided by Brian Kramer.