In the Good Old Days, computers were equipped not with multigigabyte hard-disk drives but with 9-track, open-reel tape drives. A large part of the Computer Operator's job consisted of putting reels of tape on the tape drives, threading them up, taking reels of tape off the tape drives... and a fair amount of a program's time was spent moving tape back and forth, reading and/or writing a bit of tape, then moving on to another spot.
A faulty program, or faulty Job Control Language statements, could have serious consequences for the tape, for the tape drive, and for the Operator's nerves. A new program wanted to be debugged not merely with test data, but with "scratch" tapes that could suffer the slings and arrows of outrageous misFORTRAN without destroying anything valuable. Woe betide the careless operator (or programmer!) who let a buggy accounting program turn the company payroll records into 2400 feet of tangled, stretched, crinkled spaghetti on the computer room floor.
Whence, this cautionary tale:
It seems that there was a certain university that was doing experiments in behavior modification in response to brain stimulation in primates. They had this monkey with a number of electrodes embedded in its brain, all hooked up to a PDP-11. They had several programs that would stimulate different parts of the monkey's brain, and they had spent over a year training the monkey to respond to certain stimuli.
Well, eventually the PDP developed problems, and Field Service was called. Due to some miscommunication, the Field Service Representative was not informed of the delicacy of this particular setup, and the people running the experiment were not informed that Field Service was coming to fix the machine.
So the Field Service Rep proceeded to boot up the system with a diagnostic system I/O exerciser. Since the monkey was still hooked up, *it* was the "output device" that was exercised. After several minutes of gyrations, the monkey expired, its brain fried. With the monkey's loss, months of data collection were abruptly rendered worthless.
The moral, of course, is "Always mount a scratch monkey".