A clock may refer to any of the following:
1. In general, the clock refers to a microchip that regulates the timing and speed of all computer functions. In the chip is a crystal that vibrates at a specific frequency when electricity is applied. The shortest time any computer is capable of performing is one clock, or one vibration of the clock chip. The speed of a computer processor is measured in clock speed, for example, 1 MHz is one million cycles, or vibrations, a second. 2 GHz is two billion cycles, or vibrations, a second.
2. Another name for the internal clock or RTC (real-time clock).
3. A system clock or system timer is a continuous pulse that helps the computer clock keep the correct time.