Central Processing Unit Part-1

Central processing unit (CPU)is the most important part of computer system and manipulate symbols, numbers,and letters and controls other parts of the computer system. A CPU has three element primary storage, airthmatic logic unit (ALU), and control unit.

Primary storage : -

Primary memory also known as main memory,core memory,or immediate access storage, provides capability to store input data, statements from currently undergoing processing, data resulting from processing, and data in preparation for output. Data and programs are placed in primary storage before processing, between processing step, and after processing has ended,piror to being returned to secondary storage or realesed as output.

Types of semiconductor memory : -

A semiconductor is an integrated circuit made by printing  of numerous transistor on a small sillicon chip. There are several types of semiconductor memory used in primary storage. These may be two categories-Random access memory and read only memory.

Random access memory (RAM): -

RAM is a read/write memory. It is called random access because each seperate location(address) inside the memory can be accessed as easily as any other location and takes the same amount of time. RAM is extremely fast but can also be expensive. RAM is used for short term storage of data or programes instructions.

Read only memory(ROM) : -

ROM provide permanent memory storage, that is, informaton is written permanently into the memory. Data can only be read from the memory but cannot be written there. ROM is normally used to store information that the computer may need frequently for its own operation.

There are two suclasses of ROM-

1. Programmable read only memory (PROM). 

2.  Erasable programmable  read only memory(EPROM).

Arithmatic logic unit: -

Arithmatic logic unit(ALU) is used for arithmatical operations, such as addition,subtractions, multiplication, divisons,etc. In ALU the logic part used for operations ,such as comparing, selecting, matching, and sorting/merging of data.For comparing to numbers by subtracting one numberfrom the other, adder in ALU is used.

Control unit : -

Control unit, also known as nerve center of a computer system, controls and coordinates all the activities of the computer and monitors the execution of any program being processed.The CU controls and cordinates the different components of the components of the computer  inthe same way as the brain directs the action of human body.The CU does not perform the actual processing on the  data  but direct the flow of sequence of operations. The series of operations required to process a machine instruction is called the machine cycle.