Transcript Computer Component

Chapter 2
The development of computers
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Learning outcomes
• Outline the history of computers
• Explain Von-Neumann Architecture
• Explain the advantage of using the binary system in computing
and not the decimal one.
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Additional reading
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Essential
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Stallings (2003): Chapter 2.1
Further reading
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Brookshear (2003): Chapter 0.2
Schneider and Gersting (2004): Chapter 1.4
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Lesson plan
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Introduction
Definition of a computer
History of computer machines.
Hardware and software
Compilers
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Introduction
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Modern computers are:
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Small,
Fast,
Can do different things
To understand how modern computers work
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It is useful to know their development history
How is information represented ?
How is information stored?
How is information processed?
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What is a computer?
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What is a computer?
1.
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Human who performs calculations
Calculating machine
General problem solver
Machine that performs repeated
operations
Machine that can be programmed to
perform different operations
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Navigation problem
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Originally, a word computer was assigned to
humans who were employed to solve difficult
equations such as computing tabulated values
that could be used by navigators.
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Humans implies mistakes.
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Large fortune can lost.
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A computer is something that
does arithmetic sums
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Charles Babbage (mathematician) realised that
a fortune can be saved if the production of
these tables can mechanised.
There were a limited mechanic machines at
that time
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such as abacus (limited in its precision)
A Computer becomes:
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Something that does arithmetic sums.
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A computer is something that can
perform repeated operations.
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In 1822 C. Babbage proposed:
• A mechanical calculating device designed to
repeatedly add large number.
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A computer becomes:
• something that can perform repeated
operations without error.
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A computer is machine that can
perform different tasks
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1833
• C. Babbage designed a machine that could
perform different operations. Order of
operation can be changed after.
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A computer becomes:
• A machine that can be programmed to
perform different tasks.
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Abacus machine (1)
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First computer: Abacus
A rack with a sliding beads.
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Abacus machine (2)
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Emerged about 5,000 years ago in China.
Not an automated computer
Allows users to perform computations using a
system of sliding beads arranged in a rack.
Only helps to remember the current state of
calculation.
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Pascal’s System Gear
Blaise Pascal(1623-1662)
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It was developed by Blaise Pascal in 1642.
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If is also known as
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It is an 8 figure calculating machine
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Limitations: addition and subtraction only.
• Pascal mechanical calculator
• Pascaline
• Pascal’s adder.
• adding,
• subtracting, and
• carrying 10's, 100's, and 1000's
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Pascal’s System Gear
8 movable
dials
• Uses a base of 10
• add sums up 8 figures.
• When the10’s dial moves one revolution, the 100’s dial moves one notch.
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Gottfried Von Leibniz
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Leibniz developed Pascal’s ideas.
In 1671, he introduced a new device
called Step Reckoner.
The device can performs the followings:
• Addition and subtraction
• multiplication and division.
• Evaluation of square roots by series of
stepped additions.
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Babbage’s Difference Engine
Charles Babbage(1791-1871)
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It could compute tables of numbers for naval navigation,
e.g. x2 for any value of x. This machine punched the result
into a copper plate.
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For more information about Babbage’s work go to:
http://www.maxmon.com/1830ad.htm
http://en.wikipedia.org/wiki/Charles_Babbage
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Electronic Numerical Integrator
and Computer (ENIAC)
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(1943-1946) by John Mauchly
ENIAC used vacuum tubes for number
computation.
• The switches between the vacuum tubes
were able to represent 2 states: ON and OFF.
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However, programming was done
manually.
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17,468 vacuum tubes
70,000 resistor
6,000 manual switches
30 tones weight
Covers 167 square metres
160 kilowatts of electric power
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Von Neumann Machine
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Invented in 1943 by John Von Neumann
First machine that could perform all operations
electronically.
No manual switching between states is needed
It consists of :
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A central processing unit
Memory as well as Input/Output devices
These were connected through a system bus (set of
wires)
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Von Neumann architecture
CPU
Main
memory
Add. bus
Data bus
Control bus
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Industry Standard Architecture
ISA & Binary System
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John von Neumann’s architecture was also
referred to as ISA machine
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The ISA used vacuum tubes that were based
on the binary system.
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The invention of transistors in 1947 (semiconductor with 2 states) favoured the binary
system to the decimal one.
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Computers since the 1940’s
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1st generation (1943-59): Bulky machines using vacuum tubes.
2nd generation (1959-65): Transistor-based machines with magnetic
core memory, programmed with high level languages (e.g. Fortran
or Cobol).
3rd generation (1965-75): Integrated circuits. Operating systems
permitting shared use of machines.
4th generation (1975-85): Machines built with large-scale and very
large-scale integrated circuits (VLSI), e.g. Microcomputers.
Graphical User Interfaces (GUIs), networks
5th generation (1985-present): Multimedia interfaces, mobile
computing, parallel processing. Most of today’s computers also
inherit the properties of 4th generation devices.
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Hardware and Software
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Hardware:
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Software:
• the physical components of a machine.
• Touchable
• Instructions performed by a computer
• Sequence of instructions that include
• Conditional statements
• Block of statements that are to be repeated
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Software Terminology
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Program:
• Set of instructions or rules that a computer can apply
• Software consists of a set of programs
Application program:
• An end-user employs, such word processor, web
browser, etc..
System programs:
• Manages the running of applications, such as operating
system.
• Link between the application software and the hardware
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Compilers
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Executable/Object Code:
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It is expressed in machine code.
A language the machine hardware can understand
Source Code:
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The text of a program written in high-level language.
Compiler:
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Translates from source code to object code, machine
code.
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Basic Process of Compilation
Source code
compiling
Compiler
Executable
Code
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Files and directories
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A file is collection of data (e.g. plain text
document)
Directories:
• A means of organizing files
• Usually form a hierarchy
• Root:
• is the top directory in the hierarchy
• (/ Unix and \ in Ms-dos).
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Computer Component
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Most computers consist of:
• Input/output devices: keyboard, mouse
• Visual display units: screen
• Graphical user interfaces: display on the screen that allows you to interact,
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e.g. by pointing, clicking, dragging. Objects that you see on screen, e.g.
wastebasket, folders, symbols such as disk, scissors, etc.
CPU: processor (e.g. INTEL, ) – made out of silicon
Hard-drive (magnetic disk, now more than a Terabyte)
RAM (working memory, now more than a Gigabyte)
Cards, such as graphic cards, sound cards, Ethernet cards
Operating systems, e.g. UNIX, Linux, Windows, etc
Programmes (written in assembly language, Java, C, C++, Visual Basic,
Python, Perl etc.)
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