SYS, Windows System File (.sys)
The SYS System file format
The Windows operating system as well as Microsoft DOS use files with the SYS extension. They are used to save different information about important Windows components and functions such as drivers. The most commonly known SYS file is "config.sys" which contains all necessary data and configurations that are used to run Microsoft DOS.
Technical details of SYS files
Saved in a binary text format, SYS files contain different variables, settings and functions. Those are vital for the Windows operating system to run and execute necessary programs properly. SYS files are prone to be infected with viruses and malware. Thus, it's advised to check them thoroughly before opening or executing one of them.