They're executable files for MS-DOS systems, similar to .exe but in a somewhat different internal format, generally smaller in size. On a compatible system, you should be able to run them by clicking on them in Windows or typing their name from a DOS command line. They may or may not work in modern Windows systems, which emulate old-fashioned DOS in the command line mode but aren't always 100% compatible with old stuff.
MS-DOS
Widespread
Categories
