The C/C++ Theory Q&A Thread

[KYA]

Here is the official unofficial Q&A thread for theory topics in the realm of C and C++. Theory questions (rather then actual code questions) can go here and I'll do my best to answer them.

Example of a theory question: Why do variables that are needed in multiple source files cause .obj linker errors unless they are declared extern?




Example of what NOT to post:

Code: C++ [Select]

1. //this is my program help please

Make a separate thread for that.