control variable

(control systems) One of the input variables of a control system, such as motor torque or the opening of a valve, which can be varied directly by the operator to maximize some measure of performance of the system.

In programming, a variable that keeps track of the number of iterations of a process. Its value is incremented or decremented with each iteration, and it is compared to a constant or other variable to test the end of the process or loop.

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Those variables not being studied that are held constant so as not to influence the experimental outcome. Environmental conditions, intelligence quotients, and social and psychologic variables are examples of variables that must be controlled.

An attribute used for sorting data into categories, usually for subsequent analysis or for sampling. see classification.