Commands are the instructions, also called directives, which are conveyed to a computer or an associated device. A commands specifies the performance of a task.

There are various types of commands. Some commands are certain words, called keywords, which a program can understand and execute. Function keys specify other commands. Striking the keys will initiate the execution of a pre-set command. Still other commands can be selected by scrolling down a menu of choices and selecting one, typically by using the mouse. Additionally, some commands are keyed to graphical objects, such as buttons, on the user's screen. By clicking on the graphical object, the particular command can occur.

Every program that interacts with a user has a set of commands to facilitate the interaction. This set is typically known as the user interface. The nature of these sets of commands varies from one program to another.

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