Like human beings, computers too have a ‘brain’ that processes raw information into usable data. Users input data into the computer system and it is then processed by the central processing unit or the CPU. The results of the processed data are then sent to an output device as usable data.
THE CENTRAL PROCESSING UNIT (CPU)
A Central Processing Unit or CPU is a microprocessor (or processor for short). It is an integrated circuit chip that is capable of processing electronic signals. The CPU is the most important element in a computer system.
A CPU interprets instructions given by the software and carries out those instructions by processing data and controlling the rest of the computer’s components.
Nowadays, processors are found in all kinds of electronic devices such as cell phones, calculators, automobile engines, and even industrial and medical equipment. They process information so that humans can enjoy their effective and efficient operation.
A CPU consists of two subcomponents; the Control Unit (CU) and the Arithmetic Logic Unit (ALU).
1) CONTROL UNIT (CU)
Basically the Control Unit’s main function is to direct the CPU to process data. The Control Unit extracts instructions from memory and decodes and executes them.
Under the direction of a program, the Control Unit manages a four-step basic operation which is called a machine cycle or processing cycle.
Fetch and decode is in the instruction cycle whereas execute and store is in the execution cycle. Today’s microprocessor can go through this entire four-step process billions of times per second.
FETCH
Retrieves the next program instruction from the computer’s memory.
DECODE
Determines what the program is telling the computer to do.
STORE
Stores the results to an internal register (a temporary storage location or to memory).
EXECUTE
Performs the requested instruction, such as adding two numbers or deciding which one of them is larger.
2) ARITHMETIC LOGIC UNIT (ALU)
The Arithmetic Logic Unit (ALU), as its name implies, can perform all arithmetic and logical operations. Arithmetic operation is an operation that forms a function of two numbers. This function is usually one of the class of operations: add, subtract, multiply and divide.
Logic operation is an operation on logical values, producing a Boolean result.
In general there are 16 logic operations over one or two operands; they include AND, OR, NOT, NAND, NOR, XOR and equivalence.
HOW DATA IS PROCESSED BY THE CPU
When a user starts a program, its instructions are transferred from the storage device to the memory. The user enters the data needed by the program.
The Control Unit then interprets and executes instructions in the memory. The Arithmetic Logic Unit then performs calculations on the data in the memory. As a result, information is then stored in the memory. Information can then be sent to an output device or a storage device.
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