In computer engineering, Halt and Catch Fire, known by the assembly mnemonic HCF, is an idiom referring to a computer machine code instruction that causes the computer's central processing unit (CPU) to cease meaningful operation, typically requiring a restart of the computer. It originally referred to a fictitious instruction in IBM System/360 computers (introduced in 1964), making a joke about its numerous non-obvious instruction mnemonics. With the advent of the MC6800 (introduced in 1974), a design flaw was discovered by the programmers. Due to incomplete opcode decoding, two illegal opcodes...