File type: Windows System
The SYS extension is used mostly on Windows and MS-DOS platforms by SYStem. Generally, the files with the SYS extension contain executable codes for most hardware device drivers, such as the 1394bus.sys.
These files and documents execute on kernel-mode. This is the highest possible privilege for Microsoft Windows systems. This only means that errors or loopholes can cause great damage to the documents and in worst cases; errors may lead to data loss.
How to Open SYS Files
Category: System Files
With Windows: May be viewed with a text editor, Should not be opened manually
With Linux: N/A
Two notable and widely used with this extension are the msdos.sys and config.sys.
However, these two are not the same as the other SYS as these two contain configuration parameters not in executable codes but in text form.
These two are commonly used in MS-DOS with the autoexec.bat for controlling the ways the system is boot up. However, with the modern Windows systems, these are already considered obsolete are now only utilized for backward compatibility only.