Scratch monkey

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Scratch monkey is a term used in hacker jargon, as in "Before testing or reconfiguring, always mount a scratch monkey", a proverb used to advise caution when dealing with irreplaceable data or devices.[1][2] It is used to refer to any temporary configuration changes to a computer during any risky operation, which include a replacement for some precious resource or data that might otherwise be destroyed.

The meaning is based upon the use in the 1970s of a scratch tape or other storage device, which was available for temporary use, to be loaded in place of other tapes whose valuable contents might be damaged by the operation to be performed. If a problem occurred, it would be the scratch tape that was damaged rather than the more valuable tape that had been removed.

The phrase "always mount a scratch monkey" originated from two tales by technicians about maintenance that was performed on computer equipment.[notes 1] The technicians were unaware that the computer was connected to five laboratory monkeys, and the routine maintenance procedures caused the death of three of the monkeys.[3][notes 2]


  1. ^ One story reads that the University of Toronto had taught a monkey called Mabel to swim using a gas regulator to breathe underwater. A computer technician from the hardware supplier DEC adjusted settings on the regulator that altered the gas mixture and asphyxiated Mabel.
  2. ^ In 1979 or 1980, five monkeys at the University of Toronto in the medicine department were hooked up to brainwave sensors using custom hardware. Part of the interface was a diskdrive located in a different part of the building whose read-only button was activated and taped down with a warning not to remove the adhesive tape. Drive read operations operate at a much lower current than write operations. A maintenance technician from outside the university servicing a fault removed the tape, enabled write mode and performed a drive diagnostic test. The resulting electrical current sent through the sensors stunned two monkeys and killed the other three.

External links[edit]


  1. ^ Raymond, Eric S. (October 11, 1996). The New Hacker's Dictionary (3rd ed.). MIT Press. p. 398. ISBN 0-262-68092-0.
  2. ^ "The Jargon File - scratch monkey". Retrieved December 26, 2017.
  3. ^ "Scratch Monkey Story".