Computer

Computer :

The “computer” word comes from the word “compute”, which means “to calculate”. Usually consider a computer to be a calculating device that can perform arithmetic operating at high speed. Computer is electronics device that can automatically accept and store input data, process them, and produce output results by interpreting and executing programmed instructions.

Or

Computer is an electronics machine which is capable for the following functions:

·     Accept data and Instructions at Input Device

·      Process the data according to given instructions

·      Store the data as long as required

·     Finally compute or manipulate the data or display the result on Output Devices.   

Characteristics of Computer :

§         Accuracy

§         Atomicity

§         Diligence

§         Memory (Power of Remembering)

§         High Speed

§         Versatility

§         No. I. Q.

§         No. Feelings.

Limitation of Computer :

·        Does not work by its own

·        Does not have intelligence

·        Can not take decisions on its own

·        Computers unlike humans cannot learn by experience.

·        Every instruction must be precisely entered, to make it understand by the computer.

History of Computer :

ABACUS	Originated in China in 3000 BC	Numbers are represented by shifting positions of beads on rock
Adding Machine	French Mathematician  Blasé Pascal in 1642	Consisted of dials and toothed wheels, concept of carry was used like odometer/electricity meter
Calculator	Leibniz Germany -1671	Improvement over adding machine of Pascal, it could solve roots and multiplication
Difference Engine & Analytical Engine	Charles Babbage in 1822 Father of Computer	Based on constant difference to Compute successive value in table.
Punched Cards	Dr. Herman Hollerith of US in 1880, founded  Tabulated Machine Co.	Concept of recording data by punching holes on a card.

Basic Operations :

Inputting    :	Processing of entering data and instructions into a computer system.
Storing        :	Saving data and instructions to make them readily available for initial and additional processing as when required.
Processing  :	Performing arithmetic operations or logical operations on data to convert them into useful information.
Outputting :	Process of producing useful information or results for a user, such as printed report or visual display.
Controlling :	Direct the manner and sequence in which the above operations are performed

Computer Generations :

Generation Period	Key Hardware Technology	Key Characteristics	Representative Systems
First Generation (1945-1955)	Vacuum Tube	Bulky in size, highly un reliable, limited use, costly, difficult to use.	ENIAC, EDVAC, EDSAC, UNIVAC-I, IBM-701
Second Generation (1955-1965)	Transistors	Faster, smaller, more reliable and easier to program than previous generation computer	Honeywell 400, IBM7030, CDC-1604, UNIVAC LARC
Third Generation (1965-1975)	ICs : Integrated Circuit SSI & MSI	Faster, smaller, more reliable and easier to program than previous generation computer, Scientific, commercial and interactive on-line applications.	IBM-360/370, PDP-8,            PDP-11, CDC-6600
Fourth Generation (1975 –1980)	ICs with Microprocessor , LSI Technology	Small, affordable, reliable, and easy to use PCS, more powerful and reliable mainframe systems, general purpose machines, easier to produce commercial	IBM PC, Apple-II, TRS-80, VAX-9000, CRAY-I, CRAY-2, CRAY-X/MP
Fifth Generation (1980 – Present )	ICs with Microprocessor , VLSI Technology + Artificial Intelligence	Portable computer: more powerful, cheaper, reliable, more easier to use, desktop machines: general purpose machine, WWW, Multimedia application, Internet-based application.	IBM, Pentium PCs, SUN workstation, IBM SP/2,  SGI-2000, PARAM-10000

Basic Organization of Computer System (Block Diagram)

Input Unit :

• It accepts (or reads) instructions and data from outside world.
• It converts these instructions and data into computer acceptable form.
• It supplies the converted instructions and data to computer for further processing.

An input device is an electromechanical device that accepts data from outside world and translates them into a form a computer can interpret. Several input devices are available today. These are :

1.      Keyboard

2.      Point and Draw Device

a.      Mouse

b.      Trackball

c.       Joystick

d.     Light Pen (Electronic Pen)

3.      Touch Screen

4.      Data Scanning Device

a.      Image Scanner

                                                                                        i.      Flatbed Scanner

                                                                                     ii.      Hand Held Scanner

b.      Character Reader

                                                                                        i.      Optical Character Reader (OCR)

                                                                                     ii.      Optical Mark Reader (OMR)

                                                                                   iii.      Magnetic Ink Character Reader

c.       Bar Code Reader

5.       Electronic Card Reader

6.      Speech Recognition  Devices

7.      Vision Input System (Camera)

Output Unit :

• It accepts the results produced by computers which are in coded from and hence, we cannot easily understand them.
• It converts these coded results to human acceptable from.
• It supplies the converted results to outside world.

An output Devices is an electromechanical device that accepts data from a computer and translates them into a form of suitable for use of outside world (Users). Several output device are available.  These are :

1.      Monitor

a.      Cathode Rays Tube (CRT)

b.      Liquid Crystal Display (LCD)

2.      Printer

a.      Impact Printer : Hammers typeface against paper and inked ribbon.

b.      Non- Impact Printer : No physical contact between ribbon and printing mechanism.

3.      Speaker

4.      Projector

5.      Speech Synthesizer

6.      Voice Reproduction System

Storage Unit :

·        Data and instructions required for processing (received from Input Devices)

·        Intermediated results of processing.

·        Results for Output, before they are released to an output device.

Primary Storage :

·         It is also known as its main memory, is used to hold pieces of program instructions and data, intermediate result of processing and recently produced results

·         Primary storage scan hold information only while computer system is on as soon as computer system switches off or resets, the information held in primary storage is erased.

·         It has limited amount of storage capacity because it is expensive.

·         Primary storage of modern computer systems is made of semiconductor devices. 

Secondary Storage :

·        It is also known as Auxiliary Memory, secondary storage holds the program instructions, data and information of those jobs on which the computer systems is currently not working but needs to hold them for processing later.

·        Non -Volatile in nature.

·        Large storage capacity.

                                                                                                                   

Arithmetic and Logical Unit :

It is a place where the actual execution takes place during processing; all the arithmetic calculation and comparisons are performed in ALU. During the processing data and instructions required are transferred to ALU from the primary memory. No processing is done in primary memory, almost all ALUs are designed to perform four basic arithmetic operations – addition, subtraction, multiplication and divide and logical comparisons. Finally we can say that, all arithmetic operation s and comparisons are performed. 

Control Unit :

It does not perform any actual processing on the control unit acts as Central Nervous Systems for other components of computer systems.

• It manages and coordinates the entire computer systems.
• It obtains instructions from the programme stored in main memory, interprets the instructions and issue signals causing other units of the systems to execute them.
• All major calculation and comparisons take place inside the CPU and the CPU is responsible for activating and controlling the operations of other units of the computer systems.  CPU= CU + ALU. 

Data  : 

·        A collection of facts in raw form that can become information after proper organization or processing.

·        Data are bits of factual information.

Information :

·        Processed data obtained as output of data processing. Data are arranged in the meaningful or organized form known as information.

·        Information id organized data.

·        Information is a classified and interpreted data that is being used for decisions making information is the result of processing, gathering, manipulating and organizing data in a way that adds to the knowledge of the receiver.

The activity of processing data using a computer is called data processing

Data is raw material used as input and information is processed data obtained as output of data processing

Data Processing :

·        Manual Data Processing (MDP)

·        Electronic Data Processing (EDP)

                                                                                                                       

                                                                                                                                             

Transformation of data into information

Information Systems is a set tools, techniques, procedures and technology that generate information and communication it to the user. 

  Elements of data Processing
·      Input

·        Process

·        Output

·        Storage

Attributes of Information:

• Accuracy
• Relevance
• Complete
• Cost Effectiveness [ Customer Satisfaction, Feasible]
• Timely

Use of Information :

• Specific Knowledge.
• Planning and Decision Making
• To plan day to day activities and immediate recovery actions in case errors and emergencies
• To plan the strategy for a given period, to set targets and determine how they can be met.
• For longer term policy making a company needs to review its performance, capabilities and threats by looking at summary report received from different branches.

Source of Information  :

News Paper / Magazine/Journal/Radio/TV

Quality of Information :  

 The generally accepted list of elements used in assessing information quality is as follows.

1.                  Intrinsic Information Quality :

a.      Objectivity

b.      Accuracy

c.       Believability

d.     Reputation

2.                  Contextual Information Quality :

a.      Objectivity

b.      Relevance

c.       Value-added Objectivity

d.     Timeliness

e.      Completeness

f.        Amount of Information

3.                  Representational Information Quality :

a.      Interpretability

b.      Ease of Understand

4.                  Accessibility Information Quality :

a.      Accessibility

b.      Access Security

Classification of Information :

·        Factual Vs Analytical

o       Factual :  Information supported by direct observation or verifiable facts.

o       Analytical : An interpretation or explanation of facts. 

·        Objective Vs Subjective

o       Objective  :    Information present all sides.

o       Provides opinion or evaluative information on a topic.

·        Primary Vs Secondary

o       Primary : Information presented by its originator, an original document or in its original form. It has not been published elsewhere, put into context interpreted or translated.

o       Secondary : Information that discuss, examines, surveys, restates, summarizes or repackages original primary information.

·        Scholarly Vs Popular or General

o       Scholars : Information presented by researches in a particular field usually aimed at an audiences of fellow researchers and experts in the same field.  It presents either primary or secondary information.

o       Popular or General : Information that is aimed at a wide audience of non-specialist, it is intended to appeal to the lay person more than to the experts.