brief history of computers phas151 – computer literacy i

BRIEF HISTORY OF COMPUTERS

PHAS151 – COMPUTER LITERACY I

BRIEF HISTORY OF COMPUTERSDefinition

What is a Computer? Some Popular Definitions.1.A device that

accepts datathen performs arithmetic or logic operationsthat manipulate or change the data and

finallyproduces new results ( information) from

the data. (by Rochester – Computers)

Definition

2.a machine that

can be programmed to accept data (input),process it into useful information (output),and store it away ( in a secondary storage device) for safe keeping or later use.The processing is directed by the software, but performed by the hardware.

By – Capron and Perron : Computers and Information Systems

Definition

3.A machine which inputs, processes and outputs data under the control of a stored program.

by Longman Revise Guides : Computer Science

Definition

4.is a device that works under the control of stored programs, automatically accepting, storing and processing data to produce information that is the result of that processing.

BRIEF HISTORY OF COMPUTERSThe Basic Functions of a Computer

So, when the computer processes data it actually performs a number of separate functions as follows:

1. INPUT: the computer accepts data from outside for processing within.

2. Storage: the computer holds data internally before, during and after processing.

3. Processing: the computer performs operations on the data it holds.

4. Output: the computer produces data from within for external use

BRIEF HISTORY OF COMPUTERSCOMPUTER GENERATIONS

ALL current computers are built to the basic Design postulated byJohn von Neumann and known as

Von Neumann MachinesThe detailed design of which has now reached

five Generations

Block Diagram of Von Neumann System

INPUT PROCESS OUTPU

T

PRIMARY MEMORY

SECONDARY MEMORY

The key elements in the system

Input

Process

Output

Store

COMPUTER GENERATIONSFirst

Dating from about 1945Technology : based on valve technology and

used magnetic core memory.Speed : much faster than the earlier

electromechanical machines, but were most unreliable

Consumed vast amounts of electrical powerTook up a huge amount of physical space

COMPUTER GENERATIONSFirst

Needed engineers employed by the manufacturer to be resident on site

Memory was slow and cost a great deal No large scale file store, used drums + tapes

(no disk storage)MAINFRAMES = Monsters

COMPUTER GENERATIONSSecond

Invented around 1949Technology: Use of transistor technology i.e.

replacement of valvesReduced size and power requirementsIncrease reliability though memory was still

quite large and expensive e.g. UNIVAC IIt was, for the first time, possible to buy a

computer

COMPUTER GENERATIONSThird

Dating from about 1965Technology : used Integrated Circuits( IC) or

Small Scale Integration (SSI)Used the first Silicon circuitsFurther reduction in size and much less heat

outputEvolution of semi-conductor memory helped

reduced the cost of memory.No more special air-conditioned roomsEvolution of the minicomputer

COMPUTER GENERATIONSFourth

Dating from 1970sTechnology: extended use of ICs to Large

Scale Integration (LSI) and Very Large Scale Integration (VLSI)

Considerable reduction in Size hence ‘computer on a chip’ technology

This further Miniaturization resulted in the development of the microprocessor

Home computers

COMPUTER GENERATIONSFifth

Dating from 1980sVVLSIFurther miniaturizationInvolve Ultra fast and powerful computersFeatures : parallel architecture and data a

flow rather than instruction flow philosophy.

TYPES OF COMPUTERS

Classification in the early days of the Industry was based on:

computers designed for business applications e.g. IBM 1400 series

computers designed for scientific applications e.g. IBM 7090 series

TYPES OF COMPUTERS

MAINFRAME

MINICOMPUTER

MICROCOMPUTER

SUPERCOMPUTER

TYPES OF COMPUTERSMAINFRAME

The very first typeVery expensive in terms of costMemory often organised in words of 64+ bitsCapacity of memory very high and at the top end

compared to that of other computersOften dedicated to multi-access applicationsPeripherals tended to be smaller computers and

remoteHave many processors (multiprocessor)Efficiently organised for unlimited upward

expansion

TYPES OF COMPUTERSMINICOMPUTERS

Designed sometime later than the mainframe, 1970s

Small in physical size ( compared to mainframe)

Cheaper than the available MainframesMemory organised in words of 16-24 bitsUse cheaper, and perhaps slower peripheralsHave limited upward expansionOften dedicated to a single application or

range of applications rather than being ‘general purpose’

TYPES OF COMPUTERSMICROCOMPUTERS

The starting point is the term

MICROPROCESSORMay be defined as

a computer processor on a silicon chipwhich has

circuits imprinted on a small wafer of silicon.

TYPES OF COMPUTERSMICROCOMPUTERS

Notein some cases the whole computer can be on a silicon chiphence the expression

MICROCOMPUTER

TYPES OF COMPUTERSMICROCOMPUTERS

It is more usual for the main processor to be on a single chip mounted on a circuit board with

one chip containing the Control Unit ( CU ) and Arithmetic Logic Unit (ALU)

andadditional chips for

the working storage/ memoryand for the control of data flow to and from

the peripherals

TYPES OF COMPUTERSMICROCOMPUTERS

MICROCOMPUTERIs most easily defined as

a computer which uses a microprocessor as its Central Processing Unit (CPU).

Office microcomputers are called Personal Computers (PCs) and the top of the range models are referred to as Workstations.e.g. SUN, APOLLO systems

TYPES OF COMPUTERSMICROCOMPUTERS

Aspects of MicrocomputersQuite small in physical size compared to its

predecessors – mainframe, minicomputers

Portable machinesAre becoming smaller yet more powerfulThey are machines dedicated to single-access

(personal) applicationsThe price is far less than that of its

predecessors – affordable by the individual

TYPES OF COMPUTERSMICROCOMPUTERS

Kinds of Personal Computers ( PCs)Desktop Unit – flat based system unitTower UnitLaptops/NotebooksSubnotebooksPersonal Digital AssistantsMicrocomputer and NetworksServersMicrocontrollers

TYPES OF COMPUTERSMICROCOMPUTERS

Kinds of Personal Computers ( PCs)Desktop Unit – flat based system unit

are small computers with system units that can fit next to a desk, on a desk, or can be carried around

TYPES OF COMPUTERSMICROCOMPUTERS

Kinds of Personal Computers ( PCs)Tower Unit – tall system unit

have system units that are higher than they are wide and can be placed on the floor

TYPES OF COMPUTERSMICROCOMPUTERS

Kinds of Personal Computers ( PCs)Laptops / Notebooks

This is a portable PC, may be either AC-powered, battery-powered, or both.these computers are ideal for users who have to work away from home – combines the power of PC with mobility.

TYPES OF COMPUTERSMICROCOMPUTERS

Kinds of Personal Computers ( PCs)Subnotebooks

are smaller notebooks with less display/monitor and keyboard capabilities

to enable less weight they typically have an external floppy disk drive

TYPES OF COMPUTERSMICROCOMPUTERS

Kinds of Personal Computers ( PCs)Personal Digital Assistants ( PDAs )

are much smaller that the subnotebooksthey combine

pen input writing recognition personal organizational tools and communication capabilities in a very small

package.

e.g. Palmtops , Electronic Organizers

TYPES OF COMPUTERSMICROCOMPUTERS

Kinds of Personal Computers ( PCs)Microcomputers and Networks

PCs are now found in most businessesUseeither as Standalone machines Connected to a Network

such as Local Area Network ( LAN )connects, usually by a special cable, a

group of PCs and peripheral devices in an office or a building.

TYPES OF COMPUTERSMICROCOMPUTERS

Kinds of Personal Computers ( PCs)Microcomputers and Networks

ServerIn most LANs, one PC is assigned the

role of servermeaning that it stores data and

software for use by the other PCs and/or performs services for them , such as printing

TYPES OF COMPUTERSMICROCOMPUTERS

Kinds of Personal Computers ( PCs)Microcontrollers

also called embedded dedicated hidden computers

they are tiny computers installed in ‘smart’ or ‘intelligent’

appliances

TYPES OF COMPUTERSMICROCOMPUTERS

Kinds of Personal Computers ( PCs)Microcontrollers

like pocket calculatorsmicrowave oventraffic lightradiosmobile phones

they are dedicated performing a restricted number of tasks

TYPES OF COMPUTERSSUPERCOMPUTERS

These are machines produced with the following philosophy

the machine must run as fast as possible the capacity must be as great as

possible peripherals should be as fast as

possible, consistent with maximum capacity available

there is little or no restriction on price, i.e. money is no object.

TYPES OF COMPUTERSSUPERCOMPUTERS

AspectsFirst developed in the 1970sThe fastest and highest-capacity computersUsed for researchHave hundreds to thousands of processors

TYPES OF COMPUTERSSUPERCOMPUTERS

ExamplesCRAYOPTION RED

have small but significant market, particularly in the area of number crunching i.e. processing large volumes of numeric data.

CAPABILITIES OF COMPUTERS

Characteristics of computers that make them so useful speed accuracy reliability storage capability productivity decision-making cost reduction

CAPABILITIES OF COMPUTERS

Speedbasically the processor speed performing millions and millions of instructions/operations in

nanoseconds 1/100,000,000 seconds

microseconds 1/1,000,000 seconds

CAPABILITIES OF COMPUTERS

Accuracyprovide the microprocessor with the correct instructions

then planned operations can be repeated millions of times without a single errorGarbage In Garbage Out ( GIGO)

concept applieserrors can occurmake errors only when there is a

breakdown in the computing system

CAPABILITIES OF COMPUTERS

Storage capabilitycan store tremendous amounts of data

efficiently sorting, finding, and retrieving at lightning speed

advantage: the capability to store volumes of data is especially important in an information

age

CAPABILITIES OF COMPUTERS

Emergent capabilitiesthe above three

speedaccuracystorage capability

are fundamental capabilities of computers

by-products of computers

CAPABILITIES OF COMPUTERS

Productivitycan increase productivity

CAPABILITIES OF COMPUTERS

Decision-making Complex situations Using problem-solving techniques Sort things out Do analyses Make choices

CAPABILITIES OF COMPUTERS

Cost Reductionbecause it improves productivity and

aids decision-making ,the computer helps to

eliminate wasteful practiceshold down the cost of labour,

energy and paper work