They had a thing on the PDP-1 called ‘The Unknown Glitch’ [“Glitch” - a kink, a less-than-fatal but irritating fuck-up]. They used to program the thing either in direct machine code, direct octal, or in DDT, In the early days it was a paper-tape machine. It was painful to assemble stuff, so they never listed out the programs. The programs and stuff just lived in there, just raw seething octal code. And one of the guys wrote a program called ‘The Unknown Glitch,’ which at random intervals would wake up, print out I AM THE UNKNOWN GLITCH. CATCH ME IF YOU CAN, and then it would relocate itself somewhere else in core memory, set a clock interrupt, and go back to sleep. There was no way to find it.
—Alan Kay, in Stewart Brand’s 1972 article for Rolling Stone: “Spacewar: Fanatic Life and Symbolic Death Among the Computer Bums”