Introduction to organization of digital computer: Now a day’s use of computer systems being a basic need for almost all works done surround us. It plays an important role in today hi-tech education system (like; online smart classes, online library etc.) as well as the business processing organization. In short we can say that computer system become the necessity part of our life either direct or indirect. So to understand about the digital computer system we have to better understand about the basic units of digital computer and how they are linked together to perform a given task.

Basically a computer system that capable to store data in terms of digits and proceeds the data in form of discrete (binary i.e. 0/1) steps form one state to the next state. The whole states of digital computer system involved binary digits which means it takes the data in the form of magnetic marker status either presence or absence and/or ON/OFF switches or relay. In these types of computer whole data is represented in the form of binary or digital. Before the use of digital computer we are using analog computers; unlike analog, digital computers can only approximate a continuum by assigning large number of digits to sate description and by proceeding in arbitrarily small steps.

Organization of Digital Computer
Figure 1: Organization of Digital Computer

 Basic units of digital computer:

To perform a task through a digital computer some of the basic units are required. These units are combining together to finish a task as per the user requirement. These are as following;

1. Input Unit: to given the outside world data to the computer system through the input units; some of the other functions perform by the input units are as follows;

  • It is capable to reads the instruction and data form the outer world or user instruction.
  • It’s converts the accepted instruction and/or data in computer acceptable form (binary formate etc.)
  • It’s next task to supplies the converted instruction to the computer system for further processing.

It’s an electromechanical device. Some of the name list of input devices of digital computer system;

  • Keyboard Devices
  • Image Scanner: Optical Character Recognition (OCR) Device, Optical Mark Reader (OMR),Bar-Code Reader, Magnetic-Ink Character Recognition (MICR)
  • Point-and-draw Devices:-Mouse, Trackball, joystick, Electronic Pen, Touch Screen
  • Data scanning Devices
  • Digitizer:-Electronic-card Reader, Voice Recognition Devices, Vision-Input System, Electronic cards based Devices, Voice recognition Devices, Vision based Devices.

2. Output Devices: Some of the following important functions performed by output units are;

  • It’s responsible to accept the resultant value after proceeding and/or produced by the computer, which are in code form; and hence it can’t be easily understood by user.
  • It converts these coded results to human acceptable and/or readable and understandable form.
  • It suppliers the converted results to the outside world.

As input device it’s also an electromechanical device. Below is the name list of output devices;

  • Monitors: LCD, CRT, TFT
  • Printers: Dot-Matrix Printer, Inkjet Printer, Drum Printer, Laser Printer
  • Plotters: Drum Plotter, Flatbed Plotter
  • Screen image projector
  • Voice response systems

3. Storage Unit: To understand the requirement of storage unit we have to know about the function performed by the storage units.

  • The data and instructions required for processing (received from input devices).
  • Intermediate results of processing.
  • Final results of processing, before these results are released to an output device.

Main types of storage units of digital computer system: Broadly we are categorized storage units in two parts;

  • Primary Storage: Sometimes it is also knows as main memory; because it is used to hold pieces of program instruction, data, intermediate results of processing data and recently result produced by processing.
  • Secondary Storage: The secondary storage, also known as auxiliary storage, is used to take care of the limitations of the primary storage. It is used supplement the limited storage capacity and the volatile characteristic of primary storage.

4. Central processing unit: The control unit and the arithmetic logic unit of a computer system are jointly known as the Central Processing unit (CPU). This is the brain of a computer system. In a computer system, all major calculations and comparisons are made inside the CPU, and The CPU is responsible for activating and controlling the operations of other units of the computer system.

  • Arithmetic Logic Unit: The arithmetic logic unit of a computer system is the place, where the actual execution of the instructions takes place, during the processing operation. All the comparisons (decisions) are made in the ALU.
  • Control unit: The control unit acts as a central nervous system, for the other components of the computer system. It manages and coordinates the entire computer system. It obtains instructions from the program stored in main memory, interprets the instruction, and issues signals.

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