Halt and Catch Fire

"Halt and Catch Fire" (HCF) originated as programmer humor in the 1970s to describe machine code that causes a CPU to stop functioning, requiring a reset to recover. The term was coined by Gerry Wheeler in a 1977 BYTE magazine article documenting undecumented opcodes in the Motorola 6800 processor, where certain bit patterns ($9D and $DD) would cause the chip to sequentially read through all memory without executing normal operations. While the "catch fire" part was initially a joke referencing some IBM systems that literally overheated, the term became a catch-all label for invalid opcodes and hardware bugs that lock up processors.