compiling

 compiling is the process of converting source code to machine code

but it actually consists of the following steps:

pre-processing

compiling

assembling

linking

(when we say compile, we are actually referring to these four steps, but we wont dwell on such low-level details)

pre-processing - looks for "#" , and then finds-and-replaces, copy-and-pastes

cs50 week 2 video 12:40

source: cs50