1 Computer technology [email protected] Vrije Universiteit Brussel Informatie- en Bibliotheekwetenschap, Universitaire Instelling Antwerpen

1

Computer technology

[email protected]

• Vrije Universiteit Brussel

• Informatie- en Bibliotheekwetenschap, Universitaire Instelling Antwerpen

België

For UNESCO-ODINAFRICA-MIM

June 2001

2

Computer technology: overview

• Automation

• Computers hardware

• Character encoding

• Output in general;Output to a printer

• Scanners

• Computer-peripheral interfaces

• Computer ergonomics

****

3

Computer technology

Automation

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4

Information processing: an introduction

• For an introduction to the broad subject of information processing and computer-supported information processing in particular, see encyclopedia articles like the one on “information processing” in Encyclopedia Britannica, available online and free of charge from http://www.britannica.com/

**--

http://www.britannica.com/

5

Computer technology:product segments

• Large-scale systems

• Midrange systems

• Workstations

• Personal computers

• Peripherals

• Software

• Services

• Maintenance

• Data communications

**--

6

Computer technology: phases of automation

Planning / aims /purpose / goals

Software

Hardware

Hardware

Planning / aims /purpose / goals

Software

**--

7

Components and costs of automation:initial costs

• System planning and acquisition

• Personnel + consulting + visits of other users + participation to conferences + ...

• Personnel costs during initial training + teacher(s) + ...

• Software

• Hardware

• Installation; cables

**--

8

Components and costs of automation:recurring costs

• Continuous training of personnel concerning automation

• Support and services

• Maintenance of hardware

• Software updates

• Insurance

• ...

**--

9

General evaluation criteria for computer products

• History and quality 1. of the producer? 2. of the dealer?

• Time required for delivery?

• Technical support, help, assistance

»by phone; by fax; by e-mail; (via a BBS); via WWW; via a user group; on site?

»during installation? in the future? during the weekend?

• Warranty: how long? In the case of hardware:

»Repair work and required parts free of charge?

»On-site or only carry-in?

**--

10

Computer technology: some information sources

• Journals (on microcomputers)

»PC Magazine (USA, ...)

»PC World (USA, UK, ...)

• Usenet newsgroups

»comp.*

• World-Wide Web, for instance with dictionaries:http://dir.yahoo.com/Computers_and_Internet/Information_and_Documentation/Computing_Dictionaries/

http://www.foldoc.org/

• ...

**--

http://dir.yahoo.com/Computers_and_Internet/Information_and_Documentation/Computing_Dictionaries/

http://www.foldoc.org/

11

Computer technology

Microcomputers

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12

Hardware components:the computer

• Main computer system: CPU, power supply, ports, ...

• Video/graphics card/board

• Additional RAM

• Disk drives and controllers

• Video display monitor

• ...

***-

13

Hardware components:peripherals

• Local area network hardware

• Printer

• Modem

• Power supply in the computer room + backup

• Floppy disks

• Cables

• Mouse

• Suitable furniture

• ...

***-

14

The microcomputer market shares

Intel-processor - based (Compaq, Dell, IBM, Toshiba,...) Apple

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15

Intel microprocessors:evolution

• 8088 8086

• 80286

• 80386DX 80386SX 80386SL

• 80486DX 80486SX 80486SL

• Pentium; Pentium + MMX

• Pentium II = PII

• Pentium III = PIII; Celeron

• Pentium 4

• ...

**--

16

Intel microprocessors: growing number of transistors

0500000

100000015000002000000250000030000003500000

1975 1980 1985 1990 1995

80286 80386 80486 Pentium

**--Example

17

Intel microprocessors: increasing power (in MIPS)

0

20

40

60

80

100

1975 1980 1985 1990 1995

80286 80386 80486Pentium

**--Example

18

Computer memory chips: ROM versus RAM

• Types

»ROM = Read-Only Memory (used in the BIOS, expansion cards, ...)

»RAM = Random Access Memory

»Flash-ROM = Flash-Memory = upgradeable memory, is not really ROM but RAM

• ROM is slower than RAM

**--

19

Computer memory chips: types of RAM

• DRAM = Dynamic RAM, slow but cheap

(used in main computer memory)

• SRAM = Static RAM, fast but expensive

(used for instance in memory caches)

• VRAM = Video RAM

(used in video cards)

• ...

**--

20

!? Question !? Task !? Problem !?

List and discuss criteria for the evaluation of a microcomputer.

List and discuss criteria for the evaluation of a microcomputer.

**--

21

How to buy/choose/evaluate/select a computer?

• See for instance:

»http://buy.com/

»http://cmp.shop.goto.com/

»http://computers.cnet.com/

»http://www.zdnet.com/computershopper/

• For reviews/evaluations/opinions on all kinds of products:

»http://www.epinions.com/

**--

http://buy.com/

http://cmp.shop.goto.com/

http://computers.cnet.com/

http://www.zdnet.com/computershopper/

http://www.epinions.com/

22


Read Chapter 1 about “Computer hardware “ in Part one:

Fundamental aspects of computing and related technologies, in William Saffady,

Introduction to automation for librarians, Chicago : ALA, 1999.

Read Chapter 1 about “Computer hardware “ in Part one:

Fundamental aspects of computing and related technologies, in William Saffady,

Introduction to automation for librarians, Chicago : ALA, 1999.

**--

23

Computer technology

Character encoding schemes

***-

24

Character encoding schemes: some important standards

01 ?

***-

• EBCDIC ( 8-bit)

• ASCII 7-bit 2**7 = 128

• ISO 646 8-bit 2**8 = 2**7 * 2 = 256

• Unicode 16-bit 2**16 = 256*256 = 65 536

25

Character encoding schemes: ASCII and extensions

ASCII = American Standard Code for Information Interchange:

• 128 codes, each of 7 bits, that represent the uppercase and lowercase letters of the alphabet, numbers, and some standard keyboard characters and control codes

• Many systems implement an 8-bit, extended ASCII code, which allows 2*128 = 256 characters. However, there is no standard for the upper 128 codes; the upper 128 characters vary from system to system.

***-

26

Character encoding schemes: Unicode

• 16 bits per character.

• Provides room for 2**16 = 65 536 characters.

• Universal: designed to meet the needs of the international community

• Uniform: fixed-length codes for efficiency and simplicity of programming

• Unique: with minimal duplication of character codes (important for Chinese characters)

**--

27

Computer technology

Output

**--

28

Computer graphics boards and displays: scheme

Program Program for Windows

Windows

Driver software Driver for Windows

Computer graphics board

Computer display

**--

29


Which types of computer display

do you know?

Which types of computer display

do you know?

**--

30

Computer displays: various types

• CRT = Cathode Ray TubeTraditional displays based on the same principle as television and video monitors

• Gas-Plasma displayThin display screen used in some older portable computers, also new way to build flat video and computer monitors, thin and light enough to hang on any wall

• LCD = Liquid Crystal Display A translucent glass panel using a matrix of tiny liquid crystal displays, most likely technology to replace CRT

**--

31


Which evaluation criteria do you know for displays?

Which evaluation criteria do you know for displays?

**--

32

Computer displays: some desirable properties

High contrast

High brightness

Sharp display; small dot size

Large size of the display screen

Small physical size

Low heat generation

Low power consumption

Low distortion of images

Lack of “ghosting” in the case of LCD displays

Low emission of radiation that may harm the user

Low price

**--

33

Computer displays: comparison of various types

Display type

CRTLCD

Response time

+from - to +

Heat generation

HighLow

**--

More than 1 resolution setting

yesno

34

Computer displays: ergonomics

**--

35

Computer graphics boards and displays: resolution

• Number of picture elements ( = pixels)

»horizontal

»vertical

• Colour depth (= number of colours or gray levels on the display chosen from a palette with a larger number of colours)

Example: Classical VGA: 640 horizontal x 480 vertical x 256 colours

**--

36

Computer graphics boards and displays: desirable properties

High spatial resolution

High number of colours displayable at the same time

High refresh rate = no flicker

High speed of display

**--

37

Computer graphics boards: factors determining their quality

**--

• Amount of video RAM

• Speed of the video microprocessor

• Software (“drivers”) for the communication between programs and the display

• ...

38

Computer graphics boards for microcomputers with Intel processors

Abbreviated nameMDA HGCCGAPGAEGAMCGAVGA8514/ATARGASVGAXGAXGA-2...

Origin / Creator

IBMHerculesIBMIBMIBMIBMIBMIBMAT&TconsortiumIBMIBM...

Year

1981

198719871987

1991

...

Name

Monochrome Display AdapterHercules Graphics CardColor / Graphics AdapterProfessional Graphics AdapterEnhanced Graphics AdapterMulticolor Graphics ArrayVideo Graphics Array8514/ATARGASuper VGAExtended Graphics ArrayExtended Graphics Array-2...

**--Example

39

Computer graphics boards and displays: evolution

• Many variations

confusing subject

compatibility problems

• Fast evolution to higher quality

**--

40

How to buy/choose/evaluate/select a computer display?


»http://buy.com/






**--

http://buy.com/

















41

Printer types

Type price noise quality speed Dot matrix low high + + Inkjet low low ++ -Inkjet (+PostScript) high low ++ -Laser / LED high low +++ +Laser (+PostScript) highest low +++ +

Solid ink...

**--

42

Dot matrix printers

• Produce characters by striking pins against an ink ribbon to print closely spaced dots.

• Disadvantages:

»noise

»no high quality output

**--

43

Solid ink printers

• Developed in the beginning of the 1990s by Tektronix.

• Marketed almost exclusively by Tektronix.

• They use solid wax ink sticks instead of toner.

**--

44


Which advantages offer page description languages

(such as PostScript)?

Which advantages offer page description languages

(such as PostScript)?

**--

45

Page description language interpreter in printers: advantages

• Calculates character bitmaps, thus saving space on the hard disk of the computer.

• Frees the microcomputer CPU from bitmap calculations.

• The interpreter adapts the output from the computer to the capabilities of the printer!

• Page description languages are independent of

»the type of CPU in the computer

»computer operating system

**--

46

Page description language interpreter in printers: disadvantages

• Extra costs are due to the required CPU, extra RAM and interpreter software in the printer.

• The calculations by the interpreter slow down the printer.

**--

47


Compare the spatial resolution of common displays and printers

(for black characters only).

Compare the spatial resolution of common displays and printers

(for black characters only).

**--

48

Resolution of displays and printers for

documents with black characters only

In the simple case of only black characters on a plain background:

• Common displays:

»1000 pixels per 30 cm = about 30 dots / cm

• Common printers:

»600 dpi = about 600 dots per 3 cm = about 200 dots / cm

**--

49

Colour ranges supported by video displays and printers

Range of colours supported by various processes = “gamut”

**--

Visible colour gamut

Video display gamut

Colour printer gamut

50

Computer technology

Output of characters

***-

51


Where in the system that you use are the characters (fonts) stored

that will be printed: on the computer or on the printer?

Where in the system that you use are the characters (fonts) stored

that will be printed: on the computer or on the printer?

**--

52

Printing characters: overview of various methods (1)

• Using the fixed=bitmap fonts built into the printer, or downloaded to the printer or added to the printer as an additional cassette

»Limited number of fonts

»Limited variations in size and shape of characters

»Fast

»Computer is free from tasks related to printing

»Costs of a program interpreter in the printer are avoided

**--

53

Fonts / Typefaces Fonts / Typefaces Print-outDisplay

Output of characters using bitmap fonts in the printer

UseUserrMicrocomputer

Application software

Display fonts

Display driver Printer driver

**--

54


• Using fixed=bitmap fonts on the computer system which sends these to the printer

»As many fonts available as put on the computer

»Limited variations in size and shape of characters

»Fast

»Font bitmaps take a lot of disk space on the computer

»Costs of the program interpreter in the printer are avoided

**--

55

Print-outDisplay

Output of characters using bitmap fonts in the computer

UseUserrMicrocomputer


Display fonts Printer fontsDisplay driver Printer driver

**--

56


• Using the scaleable=vectorised fonts in the printer + page description language program interpreter in the printer which creates the character bitmaps (e.g. PS)

»Limited number of fonts

»Many variations in size and shape of characters

»Fast

»Computer is free from tasks related to printing

»Costs of program interpreter in the printer

**--

57

Output of characters using scaleable fonts in the printer

UseUserr

scaleable fonts / typefaces scaleable fonts / typefaces Processing of characters to bitmapsProcessing of characters to bitmaps

Print-outDisplay

Microcomputer


Display fonts


**--

58


• Using scaleable=vectorised fonts on the computer (e.g. TrueType fonts)which creates the character bitmaps and sends these to the printer

»Many fonts


»Slow

»Fonts take some disk space on the computer

»Costs of program interpreter in the printer are avoided

**--

59

Microsoft Windows application software

Microsoft Windows

TrueType display and printer fonts


Processing of characters to bitmaps

Output of characters using TrueTypeprocessed on the computer only

UseUserr

Print-outDisplay

Microcomputer

**--

60


• Using scaleable=vectorised fonts on the computer (e.g. Adobe, TrueType) + page description language program interpreter in the printer which creates the character bitmaps (e.g. PS)

»Many fonts


»Fonts take some disk space on the computer

»Fast

»Costs of program interpreter in the printer

**--

61

Microsoft Windows application software

Microsoft Windows

TrueType display and printer fonts


Processing of characters to bitmaps for display

Output of characters using TrueType processed on computer + printer

UseUserr

InterpreterPrint-outDisplay

Microcomputer

***-

62


List and discuss criteria for the evaluation of a printer.

List and discuss criteria for the evaluation of a printer.

**--

63

How to buy/choose/evaluate/select a printer?


»http://buy.com/






**--

http://buy.com/

















64


Which method do YOU use to print from your computer?

Which method do YOU use to print from your computer?

**--

65

Computer technology

Scanners

**--

66


Which applications do you know of scanners?

Which applications do you know of scanners?

**--

67

Scanners: applications

• DTP = desk-top publishing (pictures)

• OCR = optical character recognition

• FAX

• document imaging, for archives and for document transmission using computer networks

• bar code scanning

• scanning of signatures for on-line comparison with images stored in the central computer

• ...

**--

68


Which types of scanners do you know?

Which types of scanners do you know?

**--

69

Scanners: various types

• Flatbed scanners

• Hand-held scanners

• Sheet feeding scanners

• Drum scanners

• Film scanners

• Photo CD system

• Digital cameras

• Barcode scanners

**--

70


How can a fax system be built from a computer + a scanner + ...?Which hardware and software is required?

How can a fax system be built from a computer + a scanner + ...?Which hardware and software is required?

**--

71

Scanners: number of bits per pixel

bits per pixel

• 1

• 4

• 8

• 24 = 3*8

• 30 = 3*10

• 36 = 3*12

• ...

**--

Result

line art = black or white

16 levels of gray

256 levels of gray

256 levels for each of the 3 primary colours

1 024 levels for each of the 3 primary colours

4 096 levels for each of the 3 primary colours

...

72


When a printed page is scanned at 300 dpi and 256 gray levels,

then how large is the resulting file?

How can this size be reduced?

When a printed page is scanned at 300 dpi and 256 gray levels,

then how large is the resulting file?

How can this size be reduced?

**--

73


256**3 are many colours in comparison with the limited number of colours available to a painter

for instance.

Nevertheless, it can be difficult to achieve an acceptable quality by scanning a work of art for instance.

Explain this paradox.

256**3 are many colours in comparison with the limited number of colours available to a painter

for instance.

Nevertheless, it can be difficult to achieve an acceptable quality by scanning a work of art for instance.

Explain this paradox.

**--

74


How much bigger is the resulting file, when the spatial resolution

is increased from 150 to 300 dots per inch,

without compression?

How much bigger is the resulting file, when the spatial resolution

is increased from 150 to 300 dots per inch,

without compression?

**--

75


If the number of gray levels in scanning is increased

from 2 (black or white) to 256, then how much bigger

becomes the resulting computer file?

If the number of gray levels in scanning is increased

from 2 (black or white) to 256, then how much bigger

becomes the resulting computer file?

**--

76

Scanners: how to handle gray levels

Reality:can be seen as an infinite number of gray levels

scanning and dithering to half tone

Scanned image:limited number of gray levels halftone image

Typical monochrome 300 or 600 dpi printer: output = half tone image:

black dot printed (or not) on white paper, simulating gray levels

**--

77

Scanners: the TWAIN standard

**--

• TWAIN = a standard in image acquisition

• Developed by Hewlett Packard, Kodak, Aldus, Logitech, Caere

• Advantages:

»Producers of an image acquisition device must create and deliver only one device driver file for their device.

»Developers of application software need only make their program TWAIN compliant to be able to access and control any TWAIN devices.

78

Scanners: the TWAIN standard scheme

A p p lica tio n so ftwa re 1(T W A IN co m p lia n t)

Scanner

D evice d r iver(T W A IN co m p lia n t)

(p ro v id ed b y sca n n er p ro d u cer)



U ser

**--

79


Make a scan at the highest possible resolution 1) in black and white, 2) in 256 gray levels,

of your passport, student card, or another personal document that shows text as well as a photograph.

Save the data to disk.

Prepare a sheet of paper with A) the chosen file format,

B) the resulting size of the files, C) print-outs 2 times larger than the original size.

Make a scan at the highest possible resolution 1) in black and white, 2) in 256 gray levels,

of your passport, student card, or another personal document that shows text as well as a photograph.

Save the data to disk.

Prepare a sheet of paper with A) the chosen file format,

B) the resulting size of the files, C) print-outs 2 times larger than the original size.

**--

80

How to buy/choose/evaluate/select a scanner?


»http://buy.com/






**--

http://buy.com/

















81

Computer technology

Computer-peripheral interfaces

**--

82

Computer-peripheral interfaces: general

• Terminology: interface / bus / host adapter

• Standards to control the flow of data (Input / Output) between the computer’s processor and its peripheral devices such as printers, scanners, disks, CD-ROMs, file servers (and networks in general)

• Consist of hardware + software

• Many types and sub-types

• Evolution goes on; no stability

**--

83


Which types of computer - peripheral interfaces

do you know?

Which types of computer - peripheral interfaces

do you know?

**--

84

Computer-peripheral interfaces: internal I/O buses

• ISA = Industry Standard Adapter

• MCA = Micro Channel Adapter (IBM only)

• EISA

• VESA = VL = VESA Local Bus

• PCI = Peripheral Component Interconnect;is overtaking ISA, EISA, VESA

• PC Card (was named PCMCIA earlier)

**--

85

Computer-peripheral interfaces: external I/O buses

• Parallel = Centronics

• Serial

• IDE = Integrated Drive Electronics; IDE - ATAPI

• EIDE = Enhanced IDE

• SCSI = Small Computer Systems Interface

• USB = Universal Serial Bus (since 1996)

• proprietary interfaces

**--

86

Computer-peripheral interfaces: parallel

• Mainly used to connect a printer.

• Also to connect other peripherals, including SCSI devices, by using a “shuttle”, but performance is poor.

• Enhanced version allows higher transfer speed.

**--

87

Computer-peripheral interfaces: IDE and EIDE

**--

• Proposed in 1983.

• For hard disk drives only.

• Available at low cost (in comparison with PC-cards and SCSI).

• EIDE = Enhanced IDE, proposed in 1993, supports faster data transfer rates and larger hard disk drives.

• ATAPI = Attachment Packet Interface, finalised in 1994, supports devices other than hard disk drives, for instance CD-ROM drives.

88

Computer-peripheral interfaces: SCSI

• Supports up to 7 peripherals in a daisy chain arrangement from a single host interface.

• Defines a set of software commands which allows to mix peripheral types.

• Is more expensive than EIDE.

**--

89

Computer-peripheral interfaces: USB

• Supports peripherals in a daisy chain arrangement from a single host interface.

• Defines a set of software commands which allows to mix peripheral types.

• Is less expensive than SCSI.

• Maximum data transfer rate is higher than with parallel or serial interface, but is lower than with SCSI.

**--

90

Computer technology

Computer ergonomics

**--

91

Computer ergonomics:factors determined by the system

• Radiation emitted by the display (frequency spectrum and level)

• Display quality (number of colours, resolution, size, refresh rate,...)

• Keyboard quality (size, tactile feedback, audible click or not, repeat rate,...)

• Mouse quality (grip, buttons,...)

• Audio output (volume level, usefulness,...)

**--

92

Computer ergonomics:factors determined by the user

• Lightning

»level and direction

»avoid reflections

• Position of components relative to each other

»desk, chair, computer, display, mouse, light sources,...

• ...

**--

Documents

1 Computer technology [email protected] Vrije Universiteit Brussel Informatie- en Bibliotheekwetenschap, Universitaire Instelling Antwerpen