A device that writes instructions and data into PROM chips. The bits in a new PROM are all 1s (continuous lines). The PROM programmer creates only 0s by "blowing" the middle out of the 1s.

Luckily I do this enough that buying a usb eeprom/prom programmer is cheap and trivial. Made money with it by copying a performance chip for a 1980’s Grand National for a friend.