In This Chapter
Two types of lines you see in many C programs are not C commands at all. They are preprocessor directives. A preprocessor directive always begins with a pound sign (
#). Preprocessor directives don’t cause anything to happen at runtime (when you run your program). Instead, they work during the compiling of your program.
These preprocessor directives are used most often:
Every sample program you have written so far has used
#include. This chapter finally takes the secret out of that mysterious preprocessor directive.