A text file used by MS-DOS and 16-bit versions of Microsoft Windows that is used to configure computer hardware at startup. The config.sys file is used to configure a machine’s memory, keyboard, mouse, printer, and other peripherals. The config.sys file is an ASCII file that can be edited with any text editor.
A typical config.sys file includes commands such as device, lastdrive, and dos. Device commands are used to load device drivers for different hardware, such as the extended memory driver himem.sys. Lastdrive specifies the highest available drive letter.
Dos allows you to load MS-DOS into the high memory area and to give programs access to the upper memory area.
After the config.sys file’s commands are executed, the autoexec.bat file is executed. Windows 95 and Windows 98 also include a config.sys file, but it is present only for backward compatibility with 16-bit Windows applications running under Windows 95 or Windows 98.
If a config.sys file exists in the boot partition on a computer running Windows NT, it will be parsed at startup.