A central processing unit, CPU for short, is the piece of hardware within a computer system that carries out the instructions of a computer program. This is done by performing the basic arithmetical and logical operations of the system. The form and the design of the CPU has changed as computers gets better but the fundamental operation remains the same.
They have been around since at least the 1960’s. All computers can have more than one CPU – this is called multiprocessing.
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Computer Systems 