<P> 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, but later computer developers who saw the joke created real versions of this instruction for some machines . In the case of real instructions, the implication of this expression is that, whereas in most cases in which a CPU executes an unintended instruction (a bug in the code) the computer may still be able to recover, in the case of an HCF instruction there is, by definition, no way for the system to recover without a restart . </P> <P> The expression "catch fire" in this context is normally facetious, rather than literal, referring to a total loss of CPU functionality during the current session . The imaginative idea is that the CPU chip would be switching some bus circuits so fast that it would cause them to overheat and burn . </P>

What is the meaning of halt and catch fire
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