Documentation

Main article: Software documentation
Most software has software documentation so that the end user can understand the program, what it does and how to use it. Without a clear documentation a software can be hard to use and especially if it is a very specialized and relatively complex software like the Photoshop, AutoCAD, etc.
Developer documentation may also exist, either with the code as comments and/or as separate files, detailing how the programs works and can be modified.