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1. Dr Kathy Egea COMP1900 week 3 1
2. More on computers (cont from week 2) Digitization of data
and its storage Interface as mediator COMP1900 week 3 2
3. History of computers Computer functions Bits and bytes
Software application programs and system programs Storage of data
hardware Input of data hardware COMP1900 week 3 3
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 COMP1900 week 3 4
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) COMP1900 week 3 5
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 COMP1900 week 3 7
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 COMP1900 week 3
8
9. A cross section of the magnetic surface in action. COMP1900
week 3 9
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
COMP1900 week 3 10
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. COMP1900 week 3 11
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? COMP1900 week 3 12
13. Next stage: Video: How the Altair 8800 started the PC
revolution (Part 2) Outcomes:.. Operating system Software usage
COMP1900 week 3 13
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!
COMP1900 week 3 14
15. Mac Windows Linux Red Hat UNIX Sugar OS (XO computer for
kids) COMP1900 week 3 15
16. COMP1900 week 3 16
17. Computers platform = OS + microsprocessor (CPU) Introducing
the Mac Classic Mac OS (19842001) 1984 Mac OS first commercial GUI
Mac OS X (since 2000) COMP1900 week 3 17
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 COMP1900 week 3 18
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
COMP1900 week 3
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/ COMP1900 week 3 20
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/ COMP1900 week 3 21
22. Neil Stephenson (1999) . In the beginning there was the
command line. http://www.locusmag.com/2004/Issues/08Stephenson.html
COMP1900 week 3 22
23. Intermediated experience Command line vs GUI cp Disneys
approach OS, software are intermediaries OS is a stack of metaphors
and abstractions ..to covert the information youre 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) COMP1900 week 3 23
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". COMP1900 week 3 24
25. Result of hardware + software (OS + applications) Command
line vs GUI interaction cp Disneys approach Technological
perspective: Direct control (user) vs system control (GUI) cp
Disneys immersive process Users perspective user
knowledge/preconceptions/expectation of operation; users want
meaningful interaction Basic rule: User mental model to match
system image (Normal 1988) COMP1900 week 3 25
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 COMP1900 week 3 26