Thames & Kosmos Code Gamer Experiment Manual page 61

CodeGamer
CHECK IT OUT
What is
a bug,
anyway?
▲ The logbook page with moth
When a program doesn't do what it's supposed to do, the error is called a bug. You can just call it
an error, but the term bug is used much more often. There's an amazing story behind this term!
Earlier computers, such as the Harvard Mark II, completed in 1947, did not yet have any
microprocessors. Instead, they performed calculations with the help of electromechanical relays.
A relay basically consists of an electromagnet and a magnetically activated switch. If the
electromagnet is turned on, it activates the switch. If the magnet is turned on again, it moves the
switch back to the "off" setting. The important thing is that this kind of relay involves the actual
movement of something, namely the switch.
On September 9, 1947, the
technicians responsible for
the Mark II were looking
for the source of an error.
They found it: There was a
moth that had wedged
itself into a relay! The first
bug in a computer program,
in other words, literally was
an insect. The moth,
meanwhile, was dutifully
taped into the
Mark II logbook.
▲ Harvard Mark II
59
CodeGamer manual inside english.indd 59 7/19/16 12:33 PM