The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI) and is defined as one cycle per second. The hertz is an SI derived unit whose expression in terms of SI base units is s1, meaning that one hertz is the reciprocal of one second. It is named after Heinrich Rudolf Hertz (18571894), the first person to provide conclusive proof of the existence of electromagnetic waves.
In computers, most central processing units (CPU) are labeled in terms of their clock rate expressed in megahertz or gigahertz. This specification refers to the frequency of the CPU's master clock signal. This signal is a square wave, which is an electrical voltage that switches between low and high logic values at regular intervals.
