September 9: First Instance of Actual Computer Bug Being Found | This Day in History | Computer...

As a stored program computer, the Mark II read instructions of the program one at a time from a tape and executed them. This separation of data and instructions is known as the Harvard architecture. The Mark II had a peculiar programming method that was devised to ensure that the contents of a register were available when needed. The tape containing the program could encode only eight instructions, so what a particular instruction code meant depended on when it was executed. Each second was divided up into several periods, and a coded instruction could mean different things in different periods. An addition could be started in any of eight periods in the second, a multiplication could be started in any of four periods of the second, and a transfer of data could be started in any of twelve periods of the second. Although this system worked, it made the programming complicated, and it reduced the efficiency of the machine somewhat

Because of the classified nature of my work, all I can say the bugs have only gotten bigger since then.

LCDR Andy Hill - I remember that movie