This document is a series of lecture slides on computer fundamentals. It covers topics like the history of computers from mainframes to microprocessors, operating systems like Windows, Mac OS, Linux, and Sugar OS. It discusses computer hardware components like the CPU, memory, storage, and input/output devices. It also explains key concepts such as bits, bytes, binary notation, and how data is stored on a hard drive in sectors and clusters. The document compares command line and graphical user interface approaches and how operating systems act as intermediaries between users and hardware.

1. Dr Kathy Egea
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2.  More on computers (cont from week 2)
◦ Digitization of data and its storage
 Interface as mediator…
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3.  History of computers
 Computer functions
 Bits and bytes
 Software – application programs and system
programs
 Storage of data – hardware
 Input of data – hardware
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4.  bits
◦ Bits are tiny electrical components that can hold a
very small positive charge (represented as 1) or
negative charge (represented as 0)
◦ speed of processing data is described in bits
 bytes
◦ One byte is divided into 8 bits (binary digit)
◦ A byte can store a letter of alphabet or a small
number, see next page
◦ storage of data (ie in computer memory) is divided
into these tiny storage locations described in bytes
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5.  Bit – 0 or 1
byte = 8 bits
 Eg 10011101
 This represents the number 157, How?
 Using binary notation
◦ Each position is a power of 2, with the lowest power
on the left
◦ Compare with the decimal system 245
◦ 235 = 200 + 30 + 5
= 2 * 102 + 3 * 101 + 5 * 100 ( note that 100 = 1)
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6. 1 0 0 1 1 1 0 1
20 (=1)
21 (= 2)
22 (= 4)
23 (= 8)
24 (=16)
25 (=32)
26 (=64)
27 (=128)
10011101 = 1 * 27 + 0*26+ 0 * 25 + 1 *24 + 1 * 23 + 1 * 22+ 0 * 21 + 1 * 20
= 1 * 128 + 0*64 + 0 * 32 + 1 *16 + 1 * 8 + 1 * 4 + 0 * 2 + 1 * 1
= 128 + 0 + 0 + 16 + 8 + 4+ 0 + 1
= 157
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7. Any digital data
 Numbers
 Characters
 images (Pixels) – see
image
 Music – digitized sound
wave (samples)
◦ Quality CD song is divided
into 44,000 samples per
second
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8. Hard drive disk (Magnetic storage)
– data stored in concentric circles called tracks;
- pie shaded wedges – sectors;
- cluster is a group of sectors on one track
- drive stores an index of all the sector (and track) numbers
in a table
Disk structure:
(A) track
(B) geometrical sector
(C) track sector
(D) cluster
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9. A cross section of the magnetic surface in action.
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10.  Saving a file
◦ Computer looks at the table to see what clusters
are free, record the file information on the available
clusters ( ie writes the bits that make up the file on
one or more clusters of the drive)
 Opening a file
◦ computer searches the table to locate marker for
clusters, locates the file data and reads the file
 Deleting a file
◦ delete only the reference in the table
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11.  First computers were mainframes (eg IBM 360)
 Computers work using programs (set of
instructions)
 CPU or processor executes these programs
 Program entry via
◦ Teletype (line by line interaction with computer)
◦ Batch mode processing (series of cards with holes)
 Process could take all night to get output from the computer
 Ie big calculator.
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12.  Invention of microprocessor – 1972
 Intel 8080 (1973) – 8 bit processor
 First PC - Altair 8800 cost $395
 Video –
◦ How the Altair 8800 started the PC revolution (Part 1)
 So what does the Altair do? How?
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13.  Next stage:
 Video: How the Altair 8800 started the PC revolution (Part 2)
 Outcomes:..
 Operating system
 Software usage
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14.  Jobs and Woznaik – founders of Apple
◦ idea to selling formation processing machines for
use in the home (1982)
◦ Video: advertising campaign for Macintosh
◦ (physical reality)
 Bill Gates and Paul Allen
◦ Idea to sell computer operating systems
◦ Video: foundation of Microsoft
◦ No physical reality – it came in a disk!
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15.  Mac
 Windows
 Linux
 Red Hat
 UNIX
 Sugar OS (XO computer for kids)
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16. COMP1900 week 3 16

17.  Computers platform
 = OS + microsprocessor (CPU)
Introducing the Mac
Classic Mac OS (1984–2001)
1984 –
Mac OS first commercial GUI
 Mac OS X (since 2000)
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18.  Windows PC (Bill Gates)
 1985 – Windows 1.0
 The first version of Microsoft Windows
included
◦ Windows Paint, a simple graphics paint program
◦ Windows Write, a simple word processor
◦ An appointment calendar
◦ A cardfiler
◦ MS notepad
◦ A clock
◦ A control panel
◦ Game called Reversi
◦ Clipboard
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19.  MAC OS vs Windows OS
◦ not interchangeable
◦ Different processors, and software platform
dependent
Mac system better reliability, better documentary
recovery, but more expensive that PCs
◦ Mac OS X Leopard built on UNIX OS with intel chip
Now designed to share same files
◦ Today Mac and Windows – very similar GUI
◦ Video: Microsoft's Vista Copies Apple OS?
Jan 2007, New York Times Technology :
http://www.youtube.com/watch?v=JKuYQwm1yNs&feature=related
19
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20. Linux
 ‘Linux is a free Unix-type operating system
originally created by Linus Torvalds with the
assistance of developers around the world.
Developed under the GNU General Public
License , the source code for Linux is freely
available to everyone’
 See http://www.linux.org/
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21.  One Laptop per child’
 XO computer, uses Sugar OS
◦ focuses on activities rather than applications, first screen has
icons representing home, friends, neighbourhood
 Computer has built in microphone, and webcam for mm
creations
 Emphasis is on learning by exploring and expressing
 collaborate, wireless mesh network
◦ potential for every activity to be networked, browsing, extend
community beyond borders
 Uses a journaling technique for file management –
records what the children have done looking like a scrap
book of events
http://www.olpcnews.com/
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22.  Neil Stephenson (1999) .
 In the beginning there was the command line.
◦ http://www.locusmag.com/2004/Issues/08Stephenson.html
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23.  Intermediated experience
◦ Command line vs GUI cp Disney’s approach
◦ OS, software are intermediaries
 OS is a stack of metaphors and abstractions ..to covert
the information you’re working on.. into the necklace
of bytes that are the only things computers know how
to work with. Stephenson (1999, p7).
 Structure
◦ GUI interface access to OS , hardware, software,
networks, internet
◦ File system access to hard drive (HD)
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24.  Operating system, and application software,
are intermediaries
◦ "Disney does mediated experiences better than
anyone. If they understood what OSes are, and why
people use them, they could crush Microsoft in a
year or two." from "In the beginning".
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25. Result of hardware + software (OS + applications)
◦ Command line vs GUI interaction cp Disney’s approach
◦ Technological perspective:
 Direct control (user) vs system control (GUI) cp Disney’s
immersive process
◦ User’s perspective
 user knowledge/preconceptions/expectation of operation;
 users want meaningful interaction
 Basic rule:
◦ User mental model to match system image (Normal
1988)
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26.  Desktop/GUI gives access to
◦ file system, operating system, network,
internet/www
 different layers of intermediary action
◦ network (OSI), hardware, operating system,
and software
 file system gives access to hard-drives
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27. End
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