GHz is a clock frequency called a clock rate or clock rate, representing a period of time when talking about a PC processor or processor. 

An oscillator circuit offers a little bit of energy to some crystal each minute that’s calculated in MHz or GHz, where “Hz” may be the acronym of Hertz, “M” addressing Super, or one million, and “H” addressing Giga, or a thousand million.

Along with MHz and GHz, there’s 1000 Hz, or KHz. The initial customer 1GHz processors were introduced in 2000.
While gigahertz is most commonly used to measure processor speed, it can also measure the speed of other parts of the computer, such as the RAM and backside cache. 

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The hard disk was invented on September 13, 1956 by IBM team led by Rey Johnson (considered as “father” of the disk drive). Earlier hard disk drives were large and cumbersome devices.