The New Hacker's Dictionary

A correspondent reports a legend that "Scram" is an acronym for "Start Cutting Right Away, Man" (another less plausible variant of this legend refers to "Safety Control Rod Axe Man"; these are almost certainly both backronyms). The story goes that in the earliest nuclear power experiments the engineers recognized the possibility that the reactor wouldn't behave exactly as predicted by their mathematical models. Accordingly, they made sure that they had mechanisms in place that would rapidly drop the control rods back into the reactor. One mechanism took the form of 'scram technicians'. These individuals stood next to the ropes or cables that raised and lowered the control rods. Equipped with axes or cable-cutters, these technicians stood ready for the (literal) 'scram' command. If necessary, they would cut the cables, and gravity would expeditiously return the control rods to the reactor, thereby averting yet another kind of core dump.

Modern reactor control rods are held in place with claw-like devices, held closed by current. SCRAM switches are circuit breakers that immediately open the circuit to the rod arms, resulting in the rapid insertion and subsequent bottoming of the control rods.

scratch //

1. [from 'scratchpad'] adj. Describes a data structure or recording medium attached to a machine for testing or temporary-use purposes; one that can be scribbled on without loss. Usually in the combining forms 'scratch memory', 'scratch register', 'scratch disk', 'scratch tape', 'scratch volume'. See also scratch monkey.

2. [primarily IBM] vt. To delete (as in a file).

scratch monkey // n.

As in "Before testing or reconfiguring, always mount a scratch monkey", a proverb used to advise caution when dealing with irreplaceable data or devices. Used to refer to any scratch volume hooked to a computer during any risky operation as a replacement for some precious resource or data that might otherwise get trashed.

This term preserves the memory of Mabel, the Swimming Wonder Monkey, star of a biological research program at the University of Toronto. Mabel was not (so the legend goes) your ordinary monkey; the university had spent years teaching her how to swim, breathing through a regulator, in order to study the effects of different gas mixtures on her physiology. Mabel suffered an untimely demise one day when a DEC field circus engineer troubleshooting a crash on the program's VAX inadvertently interfered with some custom hardware that was wired to Mabel.

It is reported that, after calming down an understandably irate customer sufficiently to ascertain the facts of the matter, a DEC troubleshooter called up the field circus manager responsible and asked him sweetly, "Can you swim?"

Not all the consequences to humans were so amusing; the sysop of the machine in question was nearly thrown in jail at the behest of certain clueless droids at the local 'humane' society. The moral is clear: When in doubt, always mount a scratch monkey.