CentralNotice Halt and Catch Fire From Wikipedia, the free encyclopedia Jump to: navigation , search For the television series, see Halt and Catch Fire (TV series) . Halt and Catch Fire , known by the mnemonic HCF , refers to several computer machine code instructions that cause a computer's CPU to cease meaningful operation. The expression "catch fire" is intended as a joke; the CPU does not literally catch fire, but it does stop functioning. It is also occasionally referred to as "SDI" for "Self Destruct Immediate". 1 In early CPUs 2 In modern CPUs 2.1 Motorola 6800 3 See also 4 References 5 External links In early CPUs [ edit ] In a computer's assembly language , mnemonics are used that are directly equivalent to machine code instructions. The mnemonics are frequently three letters long, such as ADD, CMP (to compare two numbers), and JMP (jump to a ...