Command in IT Glossary

An instruction to a computer or device to perform a specific task.
Commands come in different forms. They can be:
special words (keywords) that a program understands.
function keys choices in a menu buttons or other graphical
objects on your screen Every program that interacts with people
responds to a specific set of commands.
The set of commands and the syntax for entering them is
called the user interface and varies from one program to another.

The DOS operating system makes a distinction between internal
and external commands. Internal commands are commands,
such as COPY and DIR, that can be handled by
the COMMAND.COM program. External commands
include the names of all other COM files,
as well as EXE and BAT files.

Another word for command is directive.