A COM file is a type of simple executable file. On the Digital Equipment operating systems of the 1970s,.COM was used as a filename extension for text files containing commands to be issued to the operating system. With the introduction of CP/M, the type of files commonly associated with COM extension changed to that of executable files. This convention was later carried over to MS-DOS. Even when complemented by the more general.exe file format for executables, the compact COM files remained viable and frequently used in MS-DOS.