JargonFile/entries/software rot.txt

software rot

n. Term used to describe the tendency of software that has not been used in
a while to lose ; such failure may be semi-humorously ascribed to bit rot.
More commonly, software rot strikes when a program's assumptions become out
of date. If the design was insufficiently robust , this may cause it to fail
in mysterious ways. Syn. code rot. See also link rot. For example, owing to
endemic shortsightedness in the design of COBOL programs, a good number of
them succumbed to software rot when their 2-digit year counters underwent
wrap around at the beginning of the year 2000. Actually, related lossages
often afflict centenarians who have to deal with computer software designed
by unimaginative clods. One such incident became the focus of a minor public
flap in 1990, when a gentleman born in 1889 applied for a driver's license
renewal in Raleigh, North Carolina. The new system refused to issue the
card, probably because with 2-digit years the ages 101 and 1 cannot be
distinguished. Historical note: Software rot in an even funnier sense than
the mythical one was a real problem on early research computers (e.g., the
R1; see grind crank ). If a program that depended on a peculiar instruction
hadn't been run in quite a while, the user might discover that the opcodes
no longer did the same things they once did. ( Hey, so-and-so needs an
instruction to do such-and-such. We can snarf this opcode, right? No one
uses it. ) Another classic example of this sprang from the time an MIT
hacker found a simple way to double the speed of the unconditional jump
instruction on a PDP-6, so he patched the hardware. Unfortunately, this
broke some fragile timing software in a music-playing program, throwing its
output out of tune. This was fixed by adding a defensive initialization
routine to compare the speed of a timing loop with the real-time clock; in
other words, it figured out how fast the PDP-6 was that day, and corrected
appropriately. Compare bit rot.