Halt and Catch Fire, known by the mnemonic HCF, refers to several computer machine code instructions that cause the CPU to cease meaningful operation. The expression "catch fire" is intended as a joke; the CPU does not usually catch fire.
In early CPUs
The HCF instruction was originally a fictitious instruction, claimed to be under development at IBM for use in their System/360 computers, along with many other amusing instructions such as "Execute Operator".
One apocryphal story about the HCF instruction goes back to the late 1960s, when computers used magnetic core memory. The story go...