Computer system

It is collection of various components to do a desired job. The job processing consists of three following stages:-

1. Data

2. Processing

3. Information

           A computer can be defined as an electronic data processing device which can read and write, compute and compare, stores and processes large volumes of data with high speed, accuracy and reliability and give us desired result. During processing it has to perform following functions:-

 Accept data from the user (input)

Accept Instruction from the user (input)

Convert data into Information (Processing)

Displays the result (Output)

Block diagram of a computer:-

                                                      The block diagram of a computer includes inputs, Central Processing Unit (CPU) and output devices. We shall discuss. We shall discuss each block in details in succeeding paragraphs.

      Input and output Devices:- These devices are instruments of interpretation and communication between humans and computers. Input devices are used for data entry purposes. Some input devices allow direct human/machine communication, while others require data to be recorded on an input medium such as a magnetisable material. A few commonly used input and output devices and media are given below:-

Input Devices:-

Card Reader

Paper tape reader

Magnetic tape drive

Magnetic disk drive

Floppy disk drive

Keyboard MICR/OCR

Input Media:-

Punched cards (Now obsolute)

Punched paper tape

Magnetic tape

Magnetic disk

Floppy disk

Paper with magnetic tape paper with ink.

Output Devies:-

Printers and plotters

VDU and graphic terminals

Floppy disk drives

Magnetic disk drive

Cartridge drive

Output Media

Paper 

CRT

Floppy disk

Magnetic disks

Cartridge disk (CD)

  

Central Processing Unit (CPU)

             The heart of any computer system is the Centrol Processing Unit (CPU) which consists of storage, Arithmatic and  Logic Unit and control elements.

Primary storage section (Main Memory of RAM):-

                                 The primary storage also called as (main memory) section is used for four purposes. Three of these relate to the data being processed.

(a). Data is fed into an input storage are where it is held until ready to be proscessed.

(b). A working storage space that is like a sheet of scratch paper is used to hold the data being processed and the intermediate results of such processing.

(c). An output storage area holds the finished results of the processing operations until they can be released.

(d). In addition to these data-related purpose, the primary storage section also contains a program storage area that holds the processing instructions.

                The separate areas used for these four purposes are not fixed by built-in physical boundaries in the storage section. Rather they can vary from one application to another.

Thus a specific physical space may store input data in one application, output result in another processing and instruction in a third. The person writing the application instructions determines how the space will be used for each job.

The Arithmatic and Logic Unit (ALU);-

                                                                 The arithmatic logic and control sections together make up the central processing unit (CPU). All calculations are performed and all comparison (decisions) are made in the arithmatic-logic section of the CPU. Once data is fed into primary storage from input device, they are held and transferred as needed to the arithmatic-logic place in primary storage. Intermediate results generated in the arithmatic-logic unit are temporarily placed in a designated working storage area until needed at a later time. Data may thus move from primary storage to the arithmatic-logic unit and back again to storage many times before the processing is completed. Once completed the final results are released to an output storage section and from there to an output device.

The control section:-

                                 

By selecting, interpreting, and seeing to the execution of program instructions, the control section of the CPU maintains order and directs the operations of the entire system. Although the control section does not process data, it acts as the central nervous system for the other data manipulating components of the computer. At the beginning of processing, the first program instruction is selected and fed into the control section from the program storage area. There it is interpreted and from their signals are sent to the other components to execute the necessary action. Further, program instructions are selcted and executed, one after another until the processing is completed.

Primary or main memory can further be divided into following sections:-

1. Read write Memory:- This memory is called as main memory of the computer. In this memory only some important information is stored.

(a). Static Memory:- In this memory a new work is done by removing the old work. It has the capability to store (0) and (1) bit.

(b). Dynamic Memory:- In this memory electricity consumed is very less. A large amount of information is stored in this memory.

(C). Read only Memory (ROM):- It is a permanent memory. It is comluters own memory. It is used to carry out BIOS.

Elements of electronic data processing:-

                       The elements of electronic data processing are as under:-

         Electronic data processing

                               ⬇

⬇                           ⬇                         ⬇  Hardwere         skinwere         softwere

Hardware:- Hardware includes all electric, electronic, mechanical, electromechanical equipments and their interconnections which go on to form a physical computer system and which are used in data processing. Hardware is generally classified ad under:-

1. Central processing unit (CPU)

2. Peripheral equipment (Input/Output and storage devices)

Softwere:- softwere is the collective term used to describe various programs which control the operation of hardware. These programs are fed into computer as strings of bits which are referred to as machine code.

Skinware:- This comprises of all personnel such as EDP Managers, System Analysis, programmer, Operators and Maintenance Engineers.