CPU is a computer acronym that stands for Central Processing Unit: the part of the computer that actually does the calculations and initiates all other activities. The invention and development of the Microprocessor, defined as a CPU on a Chip (Integrated Circuit, or IC), obsoleted the second meaning of Central Processing Unit: the large stand-alone cabinet that previously housed the Processor’s circuitry, usually adorned with flashing lights indicating the Processor’s activity.

Today, the most common place to see CPU is when using the Windows Task Manager. It displays utilization percentages in columns labelled CPU, Memory, Disk and Network. For its purposes, today’s multi-core processors are considered one CPU; for example, 50% indicates one core of a dual core processor is fully utilized.

CPU Time is another important concept still in use today. It measures how much of a Processor’s capabilities were used to perform one or more tasks, as opposed to how long the task(s) required to complete. This is important, because it indicates if additional tasks might be done at the same time, without adding another Processor.