IT 1108: computing and information

Technology
By
Joan Nakajigo
 Lecture 1
• Introduction to IT and Computing
• Computer Hardware and Software
• Computer Components
• Computer Storage, Speed and Memory
 What is information technology?
 The term Information Technology is used to describe the use
of computers in business, education and everyday life.
• In very simple terms, a computer is an
electronic machine operating under the
control of instructions stored in its own
memory
– Accepts data
– Manipulates data
– Produces results
– Stores results
• Each computer system consists of both hardware and software.
 Computers
Hardware

 is the generic name for all the pieces of physical equipment used in

computing.

 Includes all electronic and mechanical equipment

Software

 Instructions that tell hardware how to perform tasks.

 is the generic name for the different programs that enable you to use a

computer to carry out a variety of tasks and includes applications and

operating system software. Examples of operating systems, DOS, Windows
XP, Windows 7, Vista, Windows 8.
 Data Information
 Raw facts, Data that is
 figures, and • organized,
 symbols • meaningful,
• and useful
A user
Person who
communicates with a
computer or uses the
information it generates
Information Processing Cycle
 Computers
Types of Computers
 This lecture deals mainly with personal computers but most of the principles that you will
learn apply to all types of computers.

A mainframe
the largest and most
expensive of these computer
types, capable of storing vast
quantities of information
and serving many terminals.

Mainframes are used by large enterprises such as banks, insurance companies, universities and
government departments.
 Computers
A mini computer

 Is smaller, less expensive and less powerful than a mainframe, can usually

perform similar processes to a mainframe but on a smaller scale.

• is none-the-less capable of

serving a considerable number

of terminals. Mini computers
are used by medium to large
enterprises.
 Computers
 Modern PCs can be very powerful and capable of running many different

applications but are considerably smaller, cheaper and less powerful than
either mainframe or mini computers.

 A desktop model is usually significantly

cheaper than a laptop but laptops do have

the advantage of portability.
 Both types are capable of being
networked to other computers or used as
stand-alone units.
• A network computer, while similar to a standard PC, is slightly cheaper as
9

it does not have its own hard disk.

• Instead, it is linked as part of a network to a computer called a server,
which holds all the applications used by the network computers
connected to it.

• This is intended to reduce the cost of software support.

• Network computers are used in education and business but because
they are not stand-alone they are not used in the home.
1
Types of Computers

Intelligent Terminal
• A Personal Computer can be referred to as an intelligent terminal because it
can calculate and process information and control external devices.

• It can be programmed to perform various tasks and can store data on both a
temporary and a permanent basis.

1
Types of Computers

Dumb Terminal
• A dumb terminal does not have its own Central Processing Unit (or CPU)
and therefore, cannot calculate and process information and control
external devices. • It can only receive data from or
11

send data to a central system.

Dumbterminals are used in
businesses such as banks, offices
and commercial sites.

• In travel agencies, for example, they can be used to access flight and
12

tourism information and to

1
Mainparts of a Personal Computer

A typical personal computer

• Here is a typical PC or Personal Computer system that is possibly similar
to the one you are using to study this course.
11

12

1
 4/19/2016

The Central Processing Unit

The Central Processing Unit (CPU) is a silicon chip that is the real brain
of the computer. It sits inside the system unit.

13

Input devices

To put information into your PC, you need an input device. Two of the most
commonlyused are shownhere, the keyboard and the mouse.

14
Output devices

Computer systems can have many different output devices. These convert computer
data into a form that you can read and two of the most common are a screen and a
printer.

Auxiliary storage devices

When you have entered information into your computer you may need to save it for
future use. For this you need either a floppy disk or one of a variety of internal or
external auxiliary storage devices, some of which are shown here.

16

1
You have now seen that the components of a basic personal computer system
fall into four categories:

All of the pieces of hardware that are attached to the basic system unit and
controlled by the CPUare called peripheral devices or simply peripherals.

18

1
Hardware
Central Processing Unit
The CPU is the silicon chip which functions as the real 'brain' of the computer. The
system case, which contains the computer's chips and circuits, is often incorrectly
referred to as the CPU.

The CPUis responsible for the control and execution of all the computer's operations. It
accesses data from memory, carries out the intended operations and stores the result
into memory. This diagram shows how the CPU broadly communicates with other parts
of the computer.

20

17
For this lecture, you only need to understand the broad concepts of the CPU's
control unit, arithmetic and logic unit (ALU) and internal (register) memory.

Control Unit - The control unit is responsible for the control and timing of all the
tasks being performed by the CPU.

• The instruction to be carried out is decoded so that the computer

knows what action to take. Asignal to carry out this operation is then sent out
22

to the ALU. 18
Arithmetic and Logic Unit - The ALU carries out the current operation or
calculation.
• The result from the operation is temporarily stored in a special memory location
or register known as the accumulator.

Internal Memory - The Memory cells inside the CPU, called registers, are used
for the temporary storage of data needed for the current operation.
• Values to be operated on and results obtained are stored in these registers,
while the operation is being carried out.
• Once this is completed the result is moved into the computer's main memory
so that the registers can be cleared for the next operation.
24

19
• The speed at which the CPU operates is referred to as the clock speed
and is expressed in Megahertz (Mhz).
• For example:60 Mhz = 60 million cycles per second. 400 Mhz = 400
million cycles per second.

Input devices- Keyboard and Mouse

• The keyboard is the most common input device used with personal
computers to pass information to the central processing unit.

13
• A mouse can be used to control the pointer on the screen and it usually has one or
more buttons on top.
• The left mouse button is the one that is most commonly used for selecting text or
graphics on screen.
• Pressing the right mouse button displays a shortcut menu containing commands that
are relevant to the item that is selected. 27

28

21
• A single click on the left-hand button will insert the I-beam into the text
or select an icon or graphic.
• A double click on the left-hand button will open a file or select a word
for editing.
27

• Using the left-hand button will select a menu item, select and move a
graphic, create elements in a graphics program or select a range of text.
• When the right-hand mouse button is clicked a shortcut menu appears
containing commands that are specific to the item that is selected.
Clicking away from the menu closes it.
28

22
 4/19/2016

The pointer canchange shapedepending on the task being performed.

Pointer:
This type of pointer enables you to select menu items, files, icons,
graphics etc.
I-beam:
This type of pointer enables you to select, insert or edit text.

Crosshair:
This type of pointer is used to draw lines, boxes, circles etc.

30

23
Other Input devices

A scanner is used to input text, graphics and photographic material.

• If OCR (Optical Character Recognition) software is used, text is fully editable,

just as if it was keyed directly into the computer.

• Scanners are widely used in graphic studios but are also used in offices and
libraries to archive large volumes of paper-based information.

30

24
Touch screen computer systems are sometimes found in shopping malls, tourist
centers, art galleries, airports and museums.
• Pressing your finger on the specially adapted screen lets you select from
available options.
• The CPU, which is usually hidden, converts the coordinates at the point of
31

pressure and then issues necessary instructions.

• On non-touch screen systems, a mouse could achieve the same results.
Touch screens are used for POI (Point Of Information) and POS (Point Of
Sale) systems.

32

25
A digitizing or graphics tablet comprises of a flat plate, which
senses the XY co-ordinates of a pen-like unit touching its surface.

This is converted to control the movement of the pointer on the screen to

enable the input of marks, lines or data at any point.

Users of digitizing tablets could include designers, architects and

31

engineers.

32

26
Joysticks
• Similar to the ones shown below, they are mainly supplied with dedicated
electronic game systems as an alternative to a traditional keyboard or
mouse.
• The input point is controlled by swiveling the handle or by pressing buttons.

34

27
Barcode reader
• Mainly seen at supermarket and store checkouts uses either optical or
magnetic sensing methods to scan barcodes.
• They enable the quick entry of pricing and stock information.

• A barcode is a unique combination of vertical lines

together with a numeric code that is printed onto a
small label on a product's packaging.
• This carries information on the article, its country of
origin and the manufacturer for example.
• Striped bar codes are now found on most products in
our shops. 34

28
A trackball
• Is rather like an upside down mouse. The ball is rolled with the fingertips and
this moves the pointer on screen.
• Similarly a touch pad is a touch sensitive area that senses the movement of a finger
over its surface.
• Moving one finger on the trackball or the touch pad, while at the same time
35

pressing the left button with another, enables you to click and drag an item.

• These input devices are commonly found in small laptop computers where the
space both to store and use a traditional mouse is not easily available. 29
A light pen is an input device, which uses a light sensitive stylus to select
itemsor drawdirectly onto a screen or digitizing tablet.

35

36

30
Amicrophone
• Can be used to input speech and save it as digital files on a computer. The files
canthen be used in multimedia presentations.
• Speech recognition software can be used to convert these digital files into
text format.
37

Output devices-

Monitors

• Acomputer monitor may also be called a screen or Visual Display Unit, (VDU).

• The monitor on your computer is an output unit converting computer data

into human readable form. 38

31
• This makes it one of the communicating links between you and the
information in your computer, letting you see data in a way that you can
understand it.

• Like conventional TV screens, computer monitors are measured

diagonally from corner to corner.
• The standard monitor
has a size ratio of 4:3,
width to height.

40

32
• Screen resolution is a measure of the clarity of the computer
display and is usually expressed in pixels.

• A pixel (picture element) is the smallest dot that can be displayed

on a monitor.

• Low resolution gives a jagged look to text and graphics as a result of the
smaller numberof large pixels used to form the picture.

• High resolution gives greater clarity and sharpness by displaying text and
graphics using many smaller pixels.

• This is particularly important for design and graphic work.

40

33
• Graphics standards for screen resolutions (in pixels to the inch) include the
ones shown here:
• A high resolution (e.g. SVGA 1280X1024) will result in a smoother
appearance for both text and graphics.
• However, the text and graphics will appear smaller than on a monitor
43

with a lower resolution (e.g. VGA 640X480).

VGA 640X480 640X480

SVGA 800X600 800X600
SVGA 1024X768 1024X768
SVGA 1280X1024
40

1280X1024
34
• The scan rate of a screen measures the number of times the screen is
refreshed per second.
• Here you can see a simulation of how a low scan rate causes flickering and can
cause eyestrain.

40

35
• A printer is an output unit which converts computer data into printed
characters or graphics on paper.
• It's one of the most commonly used peripheral devices in general business.
• Printers can be categorized into two main types:
 Impact printers and 45

 Non-impact printers.

46

36
• Impact printers have a carbon ribbon and characters are 'hammered' onto
the paper through that carbon ribbon, just like with a typewriter.
• Non-impact printers use heat-sensitive or electrostatically charged paper to
create a printed character (as with thermal and laser printers), or a spray of
ink (in the case of ink-jet or bubble printers).

• A Dot matrix is an inexpensive impact

printer, which has lines of pins
programmed to hammer carbon
ribbon onto paper to make a dot.

• This is a noisy and slow process and produces medium quality text
46

and graphic output. With the addition of a colour ribbon, colour

output can be achieved. 37
• Dot Matrix line printers have a horizontal row of pins and the paper moves
up seven or nine times in order for a character to be printed.
• Because Dot Matrix printers work within a matrix of dots to produce the
characters, different patterns will produce different type styles (fonts) or
simple graphics. 47

48

38
• A Thermal Printer is an inexpensive non-impact printer with a stylus that is
electrically heated at the tip.
• This makes a dot on special heat- sensitive paper. Thermal printers are reliable
and cheap but slow.
• An Ink-jet or Bubble printer is also a non-impact printer. A jet of quick drying
47

ink is forced from a nozzle and acquires an electrical charge.

• The jet then passes between charged plates,

which deflect it to the correct position on
the paper. These printers can produce
inexpensive colour output.
48

39
• A laser printer is a fast, quiet but more expensive printer that produces
high quality text and graphics. In the lower price range they print single
color only.
• During the printing process, a toner cartridge inside the printer releases
fine powder that sticks to the paper wherever it is electrically charged
during the printing process.
• Colour laser, Colour Thermal Transfer
and Dye Sublimation printers are
mainly used in design studios and
publishing companies for producing
high-quality colour printed materials.
50

40
• There are a number of different ways of feeding paper into a printer and
these are the three main categories.
• Friction Feed: As with a typewriter, a single sheet of paper is gripped
between two rollers.

Cut Sheet Feeder or Tray Feed: With this type of

feed the paper is automatically drawn one sheet at a
time through the printer.
Traction Feed: Specifically designed paper (with
holes along the edges) fits over wheels with
52

corresponding spokes for the holes. As the wheels

revolve, the paper is pulled through the printer. 41
• It may be necessary to provide temporary memory storage for data being
transferred between the CPUand the peripheral.
• The device used for this is called a buffer. For example, a printer could
have a buffer where the second page of a document is stored while the
first page is still being printed.

• Plotters are mainly found in architects' or engineers'

offices for the production of large technical
drawings that are created on the computer using
one of the many specialist CAD programs.
• CAD is an acronymfor Computer Aided Design.
27
• Machine tools are sometimes controlled by computers during
certain manufacturing processes.

• Specialist Computer Aided Manufacturing

(CAM) applications or programs are used
to do this.

• LCD or LED displays are used on ATMs or cash dispensers, video recorders,
microwaves, ovens, calculators and digital watches.
• This means that a lot of us use information from tiny computers throughout
the day, without necessarily realizing it.
• LED is an acronym for Light Emitting Diode and LCD for Liquid Crystal
56

Display.
43
• Most modern PCs include an audio card combined with either headphones or
speakers, which enable them to play existing digital audio files.

Audio cards are usually available in:

• 8 bit (low quality), 16 bit (medium quality) or 32 bit (highest quality).
• Speech Synthesis software converts basic text files into digital audio output
that tries to mimic the human voice.

Uses for this technology include:

• Conversion of text based materials for computer users who are visually
impaired and telephone messaging systems.

58

44
 Memory Versus Storage
Storage
 Media and devices used to store and retrieve data, instructions, and
information.

How does storage differ

from memory?

• Stores items for future use,

rather than temporarily
• Storage is non-volatile,
rather than volatile
 Memory Versus Storage
How does volatility compare?

Contents of storage
retained when power is
off contents of storage
retained when power is
off
Screen display and contents of most RAM
(memory) erased when power is off
 Memory Versus Storage
Reading and writing
 Memory Versus Storage
Access time
• Amount of time it takes device to locate item on disk

• Defines speed of disk

storage device Memory
(RAM)

Hard Disk

Compact Disc

Floppy Disk

Tape
 Memory Versus Storage
Capacity
• Number of bytes (characters) Storage medium can hold
• The storage capacity of computers (RAM and ROM) and that of
auxiliary storage units like disks are generally given in bytes.

• A bit is 1 unit of memory represented by 1 or 0.

• Eight little bits make one BYTE.

• One BYTE stores approximately one character
(e.g. Z)
Storage devices

• Auxiliary storage devices provide permanentstorage for your data, enabling

you to name and save files and access them again later.

• There is a wide variety of media available for this purpose and new
technologies are being developed all the time.

• Stored data can usually be erased if it is no longer required and the storage
space used again.

58

50
• A disk or tape is inserted into an appropriate drive, enabling the
user to work with the files stored on it.
• This can be inside the computer or attached to it by a cable.

60

51
• A hard disk (either internal or external) is the fastest option for mass data
storage.
• However each disk has a fixed size limit depending on it's specified capacity
and cannot be expanded. The only option, if you need more storage, is to buy
another disk.
• Large capacity hard disks are becoming more common and less expensive all
the time.

60

52
 A floppy disk is an extremely cheap option
for saving small to medium amounts of
data.

• Original floppy disks were 5½" in diameter enclosed in a case but these have
now been replaced by 3½" diskettes where the actual floppy media is
61

enclosed in a rigid plastic case.

• As most PCs have floppy drives, documents can be easily transferred from
one non-networked PC to another.

• Most floppies can store up to 1.44Mb of uncompressed data (nearly 1.5

million characters).

31
 • Zip and Jaz disks, which can be internal or
external, provide reasonably economical,
fast, removable, expandable storage
options.
61

• Zip and Jaz disks come in various capacities depending on the type that is
purchased. Zip disks have a lower capacity, usually 100-250 Mb of
uncompressed data, while each Jaz disk will store 1-2Gb or more.

• The cost of each Jaz disk is not very different to the cost of a hard disk of
similar capacity. The Jaz disk has the advantage of being removable, which
enables the transfer of large amounts of data between remote systems.
31
A CD drive is needed in the PC to read the data.

• Each CD-ROMand CD-R disk can hold a vast

amount of data. Currently standard CDs hold
approximately 650Mb.
63

• The data can be audio, text, graphics and video or a combination of all of
these.

• To play audio files the PC needs a sound card and speakers or headphones.
With these in place audio disks can also be played.

64

55
 • CD-R is the acronym for Compact Disk
Recordable.
• While special CD drives known as CD writers
are needed to write to CD-R disks, they can
also be read by most standard CD-drives.

• As the actual media is inexpensive, CD-R technology provides

relatively low cost archiving for large files.
• Data on these disks cannot be erased.

56
 • DVD is the acronym for Digital Versatile Disk, though it is
sometimes also said to be short for Digital Video Disk.
• DVD technology offers a vastly superior data capacity to that of
standard CD- ROMs, enabling the playback of full feature-
length movies.
• However, to do this you also need to add a piece of hardware called a
DVD drive to your PC.
• DVD disks are sometimes encoded for specific regions, so check
before purchasing a disk that it will play on your system.
• While early versions of the technology suffered with compatibly
issues there have been improvements and the latest drives offer
68

high-speed access to both DVD and CD-ROM disks. 57

• Each media type has different characteristics in terms of cost, speed of
access to your data and storage capacity. Useful information is usually
included in the drive specification and it is important to make the right
choice depending on your needs.
• For example, if the time that it takes to access your data is critical, a tape
drive would usually offer the slowest access time and hard disks the fastest,
with removable storage devices somewhere in between.

68

58
Types of Memory
A computer uses three main types of memory.

Auxiliary Storage Memory:

This provides permanent storage for data that you wish to access again at a
69

later date. Storage media includes hard disks and

floppy disks.
Random Access Memory (RAM):
This is often referred to as main memory or working memory.
Read Only Memory (ROM):
Data held in ROM can be referenced but not changed. 70

59
• RAM is a read and write computer memory used to store temporary
data. This means that data can be written to or placed, in RAM.
• RAM contains all the work in progress, since the user last saved to
disk, so it changes constantly as the computer is used for different
69

tasks.
• Information that is held in auxiliary storage is slower to access than
data in RAMand is loaded into main memory (RAM) as it is required.
• RAM is volatile, meaning its contents are lost when the computer is
switched off.
70

60
• The typical size of RAM for a PC today is 1 to 8GB or more
and the amount of RAM can affect the speed of some
operations.

• While part of available RAM is used by the operating

system, RAM is also needed to temporarily hold any data
that you enter until that data is permanently saved to
disk.

• By increasing the amount of RAM you can improve the

performance of your PC, process more data and run more
72

complicated programs. 61
• ROM can be read repeatedly but not changed.

• The contents are fixed during the manufacture of the

computer and this non-volatile memory stays the same even
when the computer is switched off.

• ROM is used to store permanent data such as the

instructions needed to get the computer working properly
as soon as it's switched on.
Modern operating systems can use spare storage space on the
hard disk as if it is working memory and this is referred to as
Virtual memory or Virtual RAM.

74

63
• Units of computer memory are measured in bits and bytes but how does that
relate to your files?
• What if you were using a database?

77

• The speed at which the CPU operates is referred to as the clock speed. It is
expressed in Megahertz (MHz).

• For example 300 MHz = 300 Million cycles per second.

78

64
• The speed of a computer is dictated by the speed and power of the elements inside
it.
• For simple applications, speed may not be of great importance and the extra cost of
a faster computer may not be justified.
• However with some applications, particularly those dealing with large graphics, the
faster yourcomputer, the more efficiently they will run.
• It is the speed of the processor chip in your computer, which is the main
factor in determining the overall speed of your computer. Some common
processor types are shown here.

80

65
• A powerful graphics card will improve your computer performance by
displaying the screen contents faster andmore clearly.
• Increasing the amount of RAM in your computer improves its
performance and speed.
• With more RAM, more information can be held at any time in
working memory and less swapping is needed.

82

66
• Somehard disks are faster at accessing information than others.
• The amount of free space on your hard disk can also influence speed.
• If your hard disk is almost full you may find that your machine works very
slowly. This is because there is no free space for the operating system to
utilize as virtual memory.
83

84

67