Windows Troubleshooter Guide/File Extensions

When troubleshooting problematic issues, knowledge of the various types of files you may come across can be of utmost importance. One way of figuring out which files to suss out as important and not important, besides the name, is the file extension. Aside from the usual file extensions one comes across such as .docx or .jpg, these files are often unreadable using non-programming related computer programs, and even then, may not be readable at all, save for the computer itself. Most issues one finds on a computer tend to originate from a program complaining about some .exe file with a specific reference to some line in code from a .dll file.

List of Common File Extensions for Programs

File Extension	General Functionality
.exe	Double-clicking this file will run some program. Exe files can do all sorts of things, like call .dll's, modify other files, show a window, or run other .exe files. Everything you do often involves an .exe file, be it run your browser or run an app. Most shortcuts are links to these files. This file may contain code or media files.
.dll	These files contains a set of code for which programs may use to do things. The code itself can be anything, from standardized conventions on how to access some functionality of a program to instructions dictating how to use some piece of hardware. The primary purpose of seeing these files is so that the code can be shared among programs.
.bat	Double-clicking this file will run some program. Unlike .exe files, these ones can be open in a text editor and are actually executed through a terminal such as Command Prompt. All code in this file can be typed in manually, if need be.
.txt	Contains human-readable text, which can be opened by most text editors such as Word or Notepad.
.log	Essentially a .txt file with the focus of being a log for some program.
.ini	Essentially a .txt file with assignable properties for some program to read. Modifying the right vaalues in this file will change how a program operates.
.xml	Essentially a .txt file designed for the internet. Values within may be used by a program and contains a mix of code and human-readable text.