Computer Architecture

Computer system:

A system of interconnected computers that share a central storage system and various peripheral devices such as printers, scanners, or routers is called computer system. Each computer connected to the system can operate independently, but has the ability to communicate with other external devices and computers.

Computer architecture and its feature

All computers, no matter what their size, represent and process data using the same basic principles. All computers are built on architecture originally proposed by Dr. Von Neumann. The basic components of a computer system are similar.

Computer architecture can be defined as the arrangement or construction or design of different components of a computer. It defines how the different components of the computer are connected with each other. A contemporary computer system consists of input devices, output devices, central processing unit, primary storage, and secondary storage. Different components of the computer are given below:

1.Input Unit: Input Unit is connected to the CPU and is used by human beings to interact with a computer. It is responsible for providing data and instructions to the CPU. It accepts input, converts it into computer’s format and provides it to system memory. Input refers to the process of entering data, programs, commands and user responses into memory. The keyboard is the most common input device. Some other input devices include mouse, joystick, trackball, graphic tablet, light pen, touch screen, scanner, webcam, Magnetic Ink Character Recognition (MICR), Optical Character Recognition, Optical Mark Reader (OMR), voice recognition, sensor, point of sale and microphone, touch pad and so forth.

2.CPU (Central Processing Unit): CPU is responsible for processing the inputs for generating the outputs. It controls all the component of the computer. CPU executes machine instruction, manipulation of symbols, numbers, and letters and also controls the other parts. CPU contains three sub-components. They are:

-

ALU (Arithmetic and Logic Unit): It performs arithmetic and logical operations. It performs its entire task according to the control signal from CU. It comprises numbers of accumulators and registers. The arithmetic operations performed are an addition, subtraction, multiplication, and division. The logical operations performed are logical AND operation, logical OR operation, Logical NOT operation.

CU (Control Unit): CU is responsible for controlling all the components of the computer including input devices, output devices, memory devices and other components of CPU. This unit directs all operations inside the computer. It performs the data processing operations and sends control signals to various parts of the computer system.

Set of registers: Register is a temporary memory present in CPU. It is used for storing data instructions while it is being processed by CPU. CPU contains registers like MAR, MBR, TR, etc.

3. Memory Unit: Memory unit is a part of CPU where all the given instructions, data, and results are stored during the processing period. By using the unique address we can identify the location of memory. It is responsible for storing data and instructions either for a short or longer period of time. Memory is of two types:

-Primary Memory: Primary memory is used for storing data and instructions during processing .

It is the only memory which is directly accessible to CPU. It is a semiconductor memory. In memory hierarchy, it is placed in higher position due to high speed and small size. It can be directly accessed by the processor. It is expensive, faster and used in a small capacity. Examples: RAM, ROM, Cache memory

-Secondary Memory: It is the additional memory used for storing huge amount of data for a longer period of time. It is also used for transferring data from one computer to another. It is a magnetic and optical memory. In memory hierarchy, it is placed in lower position due to low speed and large size. It is usually cheaper, slower and used in a larger capacity. It is not directly accessible to CPU. Examples: CD, Floppy disk, Magnetic tape, DVD, Hard disk, pen drive, etc.

4.Output Unit: The unit which displays, records and prints the information generated by a computer is known as an output unit. The output is data that has been processed into a useful information. The output unit is responsible for providing the result after processing. It converts the output from computer’s format into user understandable format before providing it to the user.

The outputs generated by the computer are of two types.

-Soft copy Output: The output from the monitor, speaker, projector, etc. is termed as soft copy output. The user cannot touch or feel this output. This output remains with the user till the computer is in ON state. The user can modify the output .

-Hard copy output: The output from printer and plotter is termed as hard copy output. The user can touch or feel this output. After the output is generated, it remains with the user even if the computer is in OFF state. The user cannot modify the output.

Reference

Ghishing, Er.Ashim. Computer Science. Kathmandu, Nepal: Benchmark , 2008.