Transcript Introduction to Computing and the Internet

Introduction to Computing and
the Internet
CIS 110
http://homepages.gold.ac.uk/spiegel/supervisions.htm
The course organisation is based on the
University of London study guide
“Introduction to Computing and the
Internet”, published by Francis Lin (2004).
Useful textbooks:
Stallings, W. (2003). Computer Organization and Architecture:
Designing for Performance. Upper Saddle River, N.J.:
Prentice-Hall.
White, R. (2002). How Computers Work. 6th Edition. Indianapolis:
QUE.
Useful Lab exercise:
Adrian Passow’s html tutorial which is
available at:
http://doc.gold.ac.uk/~ma901ajp/HtmlLab/
1st Module: General Introduction:
Binary numbers: 01101000101010…
Bits, bytes, kilobytes, megabytes…
1 bit = either a zero or a one, e.g. 0 or 1
1 byte= 8 bits, e.g. 01101101
1 Kilo = 1000 (but 1 kilo byte = 8 bits * 1024)
1 Mega = 1 million
1 Giga = 1 billion
1 Tera = 1 trillion
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, e.g. by pointing,
clicking, dragging. Objects that you see on
screen, e.g. wastebasket, folders, symbols such
as disk, scissors, etc.
CPU: processor
Most computers consist
of…
Hard-drive
RAM
Cards, such as graphics cards, sound cards,
ethernet cards
Operating systems, e.g. UNIX, Linux, Windows,
MacOS
Programmes (written in assembly language,
Java, C, C++, Visual Basic, Python, Perl etc.)
History: 4 Major
Developments
Batch Systems: 1950s to early 60s. Use of
technology was isolated from actual work and
processed at different times (e.g. copying
financial/bookkeeping activities from forms into
the system).
Online Systems: From mid 60s onwards. As
the name suggests, activities can be processed
in real time (e.g. updating account details).
PCs: From early 80s onwards. PCs allow
individual users to develop systems that are
specialised to their own work, and to be mobile,
e.g. work from home. Examples that have
brought advances are relational databases,
spreadsheets, word processing, etc.
Traditionally, however, PCs were isolated from
organisational systems.
Networked Systems: From late 80s onwards.
Networked systems have the advantage of
connecting different individual systems into one
coherent system, e.g. by making use of servers,
letting people log in from their homes.
Prior to modern developments:
1.
2.
3.
The abacus (rows and columns that allow a skilled person
to deal with addition, subtraction, multiplication and
division).
Pascal’s and Leibniz’ computation machines: several
wheels that all carry 10 segments and the position of each
wheel represents a number (0-9) plus a carry-over lever.
The arrangements of the wheels allowed the machine to
calculate a sum and to present this sum through the
particular position of the wheels. Leibniz built a similar
machine with wheels that could do multiplication and
division as well.
Babbage’s difference engine 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. It already
processed simple algorithms and had input/output devices
as well as a mill as the processing unit.
Prior to modern developments:
4. ENIAC: whilst Babbage’s difference engine was made of
cogs, wheels and gears, ENIAC (Electronic Numerical
Integrator and Computer) used vacuum tubes for number
computation. The switches between the vacuum tubes were
able to represent 2 states: ON and OFF (much like modern
computers have switches). Programming was done
manually though.
5. Von Neumann machine: The first machine that could perform
all operations electronically and did not need any manual
switching between states. It consisted of a Central
Processing Unit, Memory as well as Input/Output devices.
These were connected through a System Bus, which is a
set of wires. The majority of present computing
architectures have this structure. John von Neumann
invented it in 1943 at the Institute for Advanced Studies in
Princeton, NJ.
Prior to modern developments:
6. The ISA Computer and the binary system
John von Neumann’s architecture was also referred to as ISA
machine. The ISA used vacuum tubes that were based on a
binary system. Whilst binary arithmetic and calculus were
introduced by Leibniz or Newton in the late 17th Century
(there is an ongoing debate between historians who was
first), the first machine based on the binary system was
developed by Zuse in 1938 (this machine was entirely
mechanical though and did not have the von Neumann
architecture yet).
The binary system was favoured over the decimal system
because transistors were invented in 1947 (at the Bell labs).
Transistors are small semi-conductor devices that have 2
states: open or closed, hence they were suitable to
represent binary numbers.
Technical aspects of
computers since the 1940s
1st generation (1943-59): Bulky machines using
relays and 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.
Technical aspects of
computers since the 1940s
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, artificial
intelligence applications, parallel processing.
Most of today’s computers also inherit the
properties of 4th generation devices.
Recent development: The
Internet
Prior to the mainstream application of the
internet, networks for specialist research groups
and the military existed.
More info: http://www.walthowe.com/navnet/history.html
One such research group is the community of
particle physicists, and there was a project at the
European Particle Physics Laboratory in Geneva
(CERN) where the WWW with its hypertext and
links was invented by Sir Tim Berners-Lee.
Recent development: The
Internet
Website of CERN:
http://public.web.cern.ch/Public/Welcome.html
Other major development under the influence of
CERN: Grid Computing
Website of Tim Berners-Lee:
http://www.w3.org/People/Berners-Lee/
Question to you
What is a server?
An answer to this question is provided in the
lecture. If you miss the lecture, you can find a
good summary at:
http://ask-leo.com/so_just_what_is_a_server_anyway.html
New challenges
Electronic commerce (amazon, easyjet, etc.)
Security threats and protection issues (firewalls)
File sharing over the internet (music files,
movies)
Problem of Plagiarism (never copy other
people’s assignments if they are available online
– as this is considered a serious offence)
Legal issues (copyright)
MEMORY
Main memory:
• stores data currently being used
• is made of semiconductor chips
• mostly temporary: data are lost when power is off
Secondary memory:
• for mass storage
• magnetic: hard disks, floppy discs)
• or visual: CD ROM, DVD
• cheap
The following demonstration is based on Francis
Lin’s lecture notes. The demonstration can be
found in full length by downloading the file from
the following links:
http://www.doc.gold.ac.uk/~mas01fl/teaching/cis106/week2/memarchit.doc
http://www.doc.gold.ac.uk/~mas01fl/teaching/cis106/week2/memconcepts.doc