PHAS151 – COMPUTER
LITERACY I
BRIEF HISTORY
OF COMPUTERS
BRIEF HISTORY OF COMPUTERS
Definition
What is a Computer? Some Popular Definitions.
1.
A device that
accepts data
then performs arithmetic or logic operations
that manipulate or change the data and finally
produces 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 COMPUTERS
The 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 COMPUTERS
COMPUTER GENERATIONS
ALL current computers are built to the basic
Design postulated by
John von Neumann and known as
Von Neumann Machines
The detailed design of which has now reached five
Generations
Block Diagram of Von Neumann System
INPUT
PROCESS
PRIMARY
MEMORY
SECONDARY
MEMORY
OUTPUT
The key elements in the system
 Input
 Process
 Output
 Store
COMPUTER GENERATIONS
First
 Dating from about 1945
 Technology : 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 power
 Took up a huge amount of physical space
COMPUTER GENERATIONS
First
 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 GENERATIONS
Second
 Invented around 1949
 Technology: Use of transistor technology i.e.
replacement of valves
 Reduced size and power requirements
 Increase reliability though memory was still quite
large and expensive e.g. UNIVAC I
 It was, for the first time, possible to buy a computer
COMPUTER GENERATIONS
Third
 Dating from about 1965
 Technology : used Integrated Circuits( IC) or Small
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Scale Integration (SSI)
Used the first Silicon circuits
Further reduction in size and much less heat output
Evolution of semi-conductor memory helped
reduced the cost of memory.
No more special air-conditioned rooms
Evolution of the minicomputer
COMPUTER GENERATIONS
Fourth
 Dating from 1970s
 Technology: 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 GENERATIONS
Fifth
 Dating from 1980s
 VVLSI
 Further miniaturization
 Involve Ultra fast and powerful computers
 Features : 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
e.g. IBM 1400 series
applications
computers designed for scientific
e.g. IBM 7090 series
applications
TYPES OF COMPUTERS
 MAINFRAME
 MINICOMPUTER
 MICROCOMPUTER
 SUPERCOMPUTER
TYPES OF COMPUTERS
MAINFRAME
 The very first type
 Very expensive in terms of cost
 Memory often organised in words of 64+ bits
 Capacity of memory very high and at the top end
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compared to that of other computers
Often dedicated to multi-access applications
Peripherals tended to be smaller computers and remote
Have many processors (multiprocessor)
Efficiently organised for unlimited upward expansion
TYPES OF COMPUTERS
MINICOMPUTERS
 Designed sometime later than the mainframe, 1970s
 Small in physical size ( compared to mainframe)
 Cheaper than the available Mainframes
 Memory organised in words of 16-24 bits
 Use cheaper, and perhaps slower peripherals
 Have limited upward expansion
 Often dedicated to a single application or range of
applications rather than being ‘general purpose’
TYPES OF COMPUTERS
MICROCOMPUTERS
The starting point is the term
 MICROPROCESSOR
May be defined as
a computer processor on a silicon chip
which has
circuits imprinted on a small wafer of silicon.
TYPES OF COMPUTERS
MICROCOMPUTERS
Note
in some cases the whole computer can be on a silicon
chip
hence the expression
MICROCOMPUTER
TYPES OF COMPUTERS
MICROCOMPUTERS
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)
and
additional chips for
the working storage/ memory
and for the control of data flow to and from the
peripherals
TYPES OF COMPUTERS
MICROCOMPUTERS
 MICROCOMPUTER
Is 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 COMPUTERS
MICROCOMPUTERS
Aspects of Microcomputers
 Quite small in physical size compared to its
predecessors – mainframe, minicomputers
 Portable machines
 Are becoming smaller yet more powerful
 They are machines dedicated to single-access
(personal) applications
 The price is far less than that of its predecessors –
affordable by the individual
TYPES OF COMPUTERS
MICROCOMPUTERS
Kinds of Personal Computers ( PCs)
 Desktop Unit – flat based system unit
 Tower Unit
 Laptops/Notebooks
 Subnotebooks
 Personal Digital Assistants
 Microcomputer and Networks
 Servers
 Microcontrollers
TYPES OF COMPUTERS
MICROCOMPUTERS
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 COMPUTERS
MICROCOMPUTERS
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 COMPUTERS
MICROCOMPUTERS
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 COMPUTERS
MICROCOMPUTERS
Kinds of Personal Computers ( PCs)
 Subnotebooks
are smaller notebooks with
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less display/monitor and keyboard capabilities
enable less weight
they typically have an external floppy disk drive
to
TYPES OF COMPUTERS
MICROCOMPUTERS
Kinds of Personal Computers ( PCs)
 Personal Digital Assistants ( PDAs )
are much smaller that the subnotebooks
they combine
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pen input
writing recognition
personal organizational tools and
communication capabilities in a very small package.
e.g. Palmtops , Electronic Organizers
TYPES OF COMPUTERS
MICROCOMPUTERS
Kinds of Personal Computers ( PCs)
 Microcomputers and Networks
PCs are now found in most businesses
Use
either as
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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 COMPUTERS
MICROCOMPUTERS
Kinds of Personal Computers ( PCs)
 Microcomputers and Networks
Server
In most LANs, one PC is assigned the role of
server
meaning that it stores data and software
for use by the other PCs and/or performs
services for them , such as printing
TYPES OF COMPUTERS
MICROCOMPUTERS
Kinds of Personal Computers ( PCs)
 Microcontrollers
also called embedded
dedicated
hidden computers
they are tiny computers installed in
‘smart’ or ‘intelligent’
appliances
TYPES OF COMPUTERS
MICROCOMPUTERS
Kinds of Personal Computers ( PCs)
 Microcontrollers
like
pocket calculators
microwave oven
traffic light
radios
mobile phones
they are dedicated performing a restricted number of
tasks
TYPES OF COMPUTERS
SUPERCOMPUTERS
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 COMPUTERS
SUPERCOMPUTERS
Aspects
 First developed in the 1970s
 The fastest and highest-capacity computers
 Used for research
 Have hundreds to thousands of processors
TYPES OF COMPUTERS
SUPERCOMPUTERS
Examples
 CRAY
 OPTION 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
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speed
accuracy
reliability
storage capability
productivity
decision-making
cost reduction
CAPABILITIES OF COMPUTERS
 Speed
basically 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
 Accuracy
provide the microprocessor with the correct
instructions
then planned operations can be repeated
millions of times without a single error
Garbage In Garbage Out ( GIGO) concept
applies
errors can occur
make errors only when there is a breakdown in
the computing system
CAPABILITIES OF COMPUTERS
 Storage capability
can 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 capabilities
the above three
speed
accuracy
storage capability
are fundamental capabilities of computers
by-products of computers
CAPABILITIES OF COMPUTERS
 Productivity
can increase productivity
CAPABILITIES OF COMPUTERS
 Decision-making
Complex situations
 Using problem-solving techniques
 Sort things out
 Do analyses
 Make choices

CAPABILITIES OF COMPUTERS
 Cost Reduction
because it improves productivity and aids
decision-making ,
the computer helps to
eliminate wasteful practices
hold down the cost of labour, energy and
paper work