Way Back When, Like Before Electric Lights Were Invented, I Worked In An Engineering Department Where The General-use Computer Was An IBM 1130.

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Way back when, like before electric lights were invented, I worked in
an engineering department where the general-use computer was an IBM 1130.
This was a standalone computer of roughly PDP-11/34 power with a disk,
console typewriter, slow line printer. Its primary I/O was a combination
card reader/punch. Some things you ought to know before proceeding futher:

1. The card reader/punch had one input hopper and two output hoppers.
Cards came from the input hopper through the read station, through the
punch station, to whichever output hopper was selected. Cards could be
read, punched, or both as the program saw fit.

2. The CPU had a "bootstrap" mode in which it read one card as the
binary image of a program and executed that program. The standard
"coldstart" card had enough program on it to read in the operating
system's startup block which then got the whole software system going.

3. The user community used the machine mostly for applications written
in FORTRAN and was largely ignorant of the details of computers and
how they work.

Still with me? Good. Naturally, _any_ card without characters printed
on it and with lots of holes all through it looked, to the uninitiated,
like the "coldstart" card that people placed at the start of their decks.
So it was a small matter to leave a few spurious cards around the computer
room and wait for the results.

My favorite was the card that just ran the deck through the reader/punch,
placing alternate cards in the other output hopper. What a delight with
long decks! One fellow was so sure he'd done something wrong that he
took his cards, reassembled them into the right order, and ran them through
_again_ with the same bogus coldstart card.

I never did work up the nerve to write the one that punched all the holes
in all the cards following.

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