<character>

(Or "ctrl", "^") One (or a pair) of modifier keys found on all modern keyboards. If the control key is held down while pressing and releasing certain other keys then a "control character" is generated, e.g. holding control and hitting "A" generates control-A (ASCII code 1). The ASCII code for the control character is generally 64 less than that for the unmodified character.

The control key does not generate any character on its own but most modern keyboards and operating systems allow a program to tell whether each of the individual keys on the keyboard (including modifier keys) is pressed at any time.

Control characters mostly have some kind of "non-printing" effect on the output such as ringing the bell (Control-G) or advancing to the next line (Control-J). Most have alternative names suggesting these functions (Bell, Line Feed, etc.).

See ASCII character table.

Abbreviation: ctrl

(01 Mar 1997)

In research, control subjects or control procedures permit comparison with experimental results. The first controlled clinical research was probably done in 1875 by the British naval surgeon James Lind who, on board the HMS Salisbury, gave sailors with scurvy either oranges or lemons or cider or vinegar or nutmeg (or another treatment) and after just six days discovered that the citrus-consuming sailors had recovered from scury, until then the scourge of extended sea voyages, while the sailors who had been given the other treatments remained uncured.

Abbreviation: ctrl

(12 Dec 1998)