4ºESO/4 T H ESO Juan Antonio Pérez 1

A central processing unit (CPU) is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logical, control and input/output (I/O) operations specified by the instructions 2

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 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. 4

 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. 5

 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. 6

 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. 7

 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 8

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 CPUs are located on the motherboard. Motherboards have a socket for this, which is specific for a certain type of processor.  A CPU gets very hot and therefore needs its own cooling system in the form of a heat sink and/or fan. 10

An arithmetic-logic unit (ALU) is the part of a computer processor (CPU) that carries out arithmetic and logic operations on the operands in computer instruction words. The control unit (CU) is a component of a computer's central processing unit (CPU) that directs operation of the processor. It tells the computer's memory, arithmetic/logic unit and input and output devices how to respond to a program's instructions. 11

VON NEWMANN 12