COMMAND 

Any order you give to the computer by entering something on the keyboard.  
A command can make changes to files or what you see on the screen of your 
computer. Some commands always do the same thing, some commands do different 
things to different files each time you use the command, depending on what 
you type on the keyboard. Many commands you give the computer are executed 
by software that comes with DOS. The INTERNAL_COMMAND and EXTERNAL_COMMAND 
definitions list these commands.

Different manufacturers call commands different things. For example, Zenith 
documentation uses the term function when talking about commands.
