What is Digital Computer and How it Works

The Atanasoff Berry Computer (ABC) was the first Electronic Digital Computer

Computer is an Electronic Data Processing machine which receive and stores large volumes of information in the form of digit (binary) and process them as per the instructions at a very high speed and produces the desired result with preselected degree of accuracy.

The internal architectural design of computers differs from one system model to another. The basic organization remains the same for all computer systems. The digital computer is a digital system that performs various computational tasks. The word digital implies that the information in the computer is represented by variables that take a limited number of discrete values. Digital Computers work on the principle of counting of numbers.

The major components of a digital computer are
A) Input Unit
B) Output Unit
C) Central Processing Unit (C.P.U)
D) Memory Unit
E) Arithmetic Logic Unit (ALU)
F) Control Unit

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A) Input Unit:

An input unit is a device which accepts the information from the user and communicates these to the computer. Information is entered in to a computer through input devices. An input device converts input information into suitable binary form acceptable to a computer.

This is the process of entering data and programs in to the computer system. The computer is an electronic machine like any other machine which takes as inputs data and performs some processing giving out processed data. Therefore, the input unit takes data from us to the computer in an organized manner for processing. Input unit present data to the C.P.U in machine readable form.

Commonly used Computer Input Devices :

• Digital camera


• Keyboard


• Microphone


• Mouse


• Scanner


• Web Cam


• Light pen


• Joy stick etc.,

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B) Output Unit:

This output unit receives information from the C.P.U and present it to the user in the desired form. The output unit or output device receive result and other information from the computer and provides them to user. This is the process of producing results from the data for getting useful information. The computer sends information to an output device in the binary form. The output produced by the computer after processing must also be kept somewhere inside the computer before being given to you in human readable form. The output is also stored inside the computer for further processing.

Commonly used Computer Output Devices :

• Monitor


• Printer


• Plotter


• Speaker


• Projector etc.,

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C) Central Processing Unit (CPU):

The CPU is the brain of any computer system. The Microprocessor or CPU is the computer's most important component. It does all the thinking for the p.c. and runs the programs. It receives data and instructions, store them temporarily then process the data as per the instructions. It controls the operation of all other components such as memory, input and output devices.

1) Memory Unit :

It is a device that can accept data or instruction, hold them and deliver then on demand at a later time. The memory unit is also referred as primary storage. The function of the memory is to store information. It stores program, data, results or any other kind of information.

2) Arithmetic Logic Unit (ALU):

This unit is used to perform all the arithmetic and logic operations, such as addition, subtraction, multiplication, division, logic and comparison, etc.,

3) Control Unit:

This unit controls the activities of all other units in the system. It receives the instructions one by one, from the program which is stored in memory. For each instruction, it informs the ALU to execute the operations specified by the instruction. It also controls the parts of computer such as input devices, output devices and secondary memory devices. It’s main function is control the transfer of data and information between various units.

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Memory Types

MEMORY UNIT AND IT'S TYPES:

There are two types of computer memory (1) Primary (2) Secondary. Primary memory is accessible directly by the processing unit. RAM is an example of primary memory. RAM stores data temporarily. RAM will loose its contents when the power is switched off or if there is power failure. Secondary memory is located outside the computer. Primary  memory is more expensive than secondary memory. Secondary storage devices to store large quantity of data for future use.

 

Memory Unit :

It is a device that can accept data or instruction, hold them and deliver then on demand at a later time. The  memory unit is also referred as primary storage.

Memory is of two types.

I. Primary Memory

II. Secondary Memory

(I). Primary Memory:

Primary Memory  is mainly of two types

(a) Random Access Memory (RAM)

(b) Read only memory (ROM)

(a) Random Access Memory (RAM)

During the executing of a program that data required by the program is stored in Ram. It provides a volatile storage, i.e. the data are lost in the even to a power failure. So Ram used to store data temporarily.

RAM is 3 types:

1. Dynamic Ram (DRAM)

2. Static Ram (SRAM)

3. Cache Memory

Dynamic Ram:

This is computer memory, that losses its memory capability once the power source is removed.

Static Ram:

This is Ram of Ram provides a static storage of data.

Cache Memory:

It is very speed memory which used to store portion of a programme from the main memory temporarily. This cache memory is more faster but more expensive. Data is transferred automatically between the buffer and primary storage.

(b) Read only memory (ROM):

In this memory, basic start up routines and BIOS (Basic Input Output Systems) are permanently loaded during the manufacturing time. It provides a non-volatile storage. i.e., the data does not get erased when the power is switched off.

ROM is 4 Types :

(a) ROM (Read Only Memory) :

This is stored at the time of manufacture of the chips

(b) Programmable Read Only Memory (PROM):

Once the chip has been programme, the recorded information can't be changed. i.e. the PROM becomes rom and the storaged information can only be read.

(c) Erasable & Programmable Read Only Memory (EPROM):

It is similar to PROM except that erasing is possible by exposing to ultraviolet Radiation.

(d) Electrically Erasable & Programmable Read Only Memory (EEPROM):

A recently developed type of memory that can be programmed and erased by electrically signals. EEPROM used in many electronic devices.

(II).Secondary Memory:

Secondary memory storage is used to store the data and program permanently.Secondary memory is located outside the computer. Secondary storage devices to store large quantity of data for future use.

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