Lp0 On Fire - History

History

The "on fire" message probably originated in the late 1950s, when high speed computerized printing was still a somewhat experimental field. The first documented fire-starting printer was a Stromberg-Carlson 5000 xerographic printer, installed around 1959 at the Lawrence Livermore National Laboratory and modified with an extended fusing oven to achieve a print speed of one page per second. In the event of a printing stall, and occasionally during normal operation, the fusing oven would heat paper to combustion. This fire risk was aggravated by the fact that if the printer continued to operate, it would essentially stoke the oven with fresh paper at high speed. There is, however, no evidence of the "lp0 on fire" message appearing in any software of the time.

As the technology matured, most large printer installations were drum printers, a type of impact printer which could print an entire line of text at once through the use of a high speed rotary printing drum. It was thought that in the event of a severe jam, the friction of paper against the drum could ignite either the paper itself, or, in a dirty machine, the accumulated paper and ink dust in the mechanism. However, it is unknown if this ever happened as there are no surviving reports of friction-related printer fires.

The line printer employed a series of status codes, specifically ready, online, and check. If the online status was set to "off" and the check status was set to "on," the operating system would interpret this as the printer running out of paper. However, if the online code was set to "on" and the check code was also set to "on", it meant that the printer still had paper, but was suffering an error (but was still running). Due to the potentially hazardous conditions which could arise in early line printers, Unix displayed the message "on fire" to motivate any system operator viewing the message to go and check on the line printer immediately.