The Central Processing Unit (CPU), or processor, is a component that acts as the brain of a computer system. Instead of actually thinking, however, it moves data around the system in ways defined by computer programmers. A CPU essentially performs three basic functions. It accepts input, processes data, and provides output. These are critically important to the operation of any computer system.
Input is the process by which external data is entered into a computer. It is mainly provided by common input devices, such as a keyboard, mouse, scanner, or modem. Once the computer analyzes the input, that data is then processed and converted into output.
Output is the end result of the processed data input into the computer system. It refers to a process by which the CPU sends data to installed devices, such as a monitor, printer, or even a running computer program. The output data can either be stored temporarily or permanently, meaning the computer must have a way to contain this data while processing is being performed. This is where memory comes in.
A computer stores data in memory, and retrieves the data it requires from either Read-Only Memory (ROM) or Random Access Memory (RAM). ROM is permanent memory that retains data even when the system is turned off. RAM is temporary memory and, therefore, any data stored there will be deleted when the system is turned off. The CPU uses RAM to store and retrieve data on an as-needed basis. For example, the instructions needed to launch a program would be stored in and retrieved from RAM.
The cache also plays an important role in the functioning of a CPU. A cache is small amount of high-speed memory that holds data. Some processors have a cache that varies in static RAM (SRAM) capacity. SRAM is considerably faster than Dynamic RAM (DRAM), which is designated for the main memory in the computer. The overall purpose of the cache is to increase the speed at which data is processed.
Data requests made by the CPU are handled by a cache controller. This can either be built into the motherboard or the processor itself. Being that cache is an internal component, it can be accessed directly and, therefore, maintain the speed of the processor. Without this component, the computer would run dramatically slower, as the processor would be forced to wait for data to be sent from the main system memory.
The CPU is not only an important element, but a crucial one. Without it, the system would not be able to function at all. This critical component also determines the overall performance any given computer system will provide.