About the autoexec.bat file

It is the acronym for automatically executed batch file which is used in MS-DOS and early versions of Windows like Windows 3.1 and Windows 95. The autoexec.bat file is positioned in the root directory and it automatically executes commands each time the system starts up.

This batch file is mostly used to set environment variables like printer, keyboard, soundcard and location of temporary files.

The autoexec.bat was created together with the config.sys file for MS-DOS and Windows operating systems and was a suitable solution to load the required files for various computer components or hardware devices and make the system run smoothly. This proved to be the best solution for older versions of operating systems until the release of Windows 95. New operating systems do not require this files however there are still cases when they are being edited and configured manually.   

The autoexec.bat file can be easily edited in MS-DOS with the help of the EDIT command while in Windows you can run the SYSEDIT command.
Here is a command in autoexec.bat file which loads the mouse driver into the memory:
LH C:\MOUSE\MOUSE.EXE