Compile Software from Source Code

Photo Artonice via Flickr / CC BY-SA 2.0

Most of the time, especially in the Windows and Mac OS X world, end users don't have to compile software. The programmers of the software write the code and then compile it into a "binary executable" for you.
However, thanks to the popularity of open-source software, where the source code is available for one and all to read and enjoy, the impetus has been put on the end-user to compile their own code if they want to use the software.
If you find yourself having to (or wanting to) compile a piece of software, don't panic. The process is fairly simple. Every piece of software is different, but here is a summary of the most common scenario for Unix-based OS such as Linux or Mac OSX. These instructions are not so useful for Windows, as apps are usually built with special GUI development tools, not command line tools.
First, you'll need a command line and a compiler.