Standard Grade Computing Studies

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Computer Systems
Frank Frame
Standard Grade Computing Studies
STANDARD GRADE COMPUTING STUDIESii
COMPUTER SYSTEMS
First published 2004
© Learning and Teaching Scotland 2004
This publication may be reproduced in whole or in part for educational purposes by schools and
colleges in Scotland provided that no profit accrues at any stage.
ISBN 1 84399 038 5
Acknowledgement
Thanks to Dorothy Tedman for her contribution to the review of the content.
iii
STANDARD GRADE COMPUTING STUDIES
COMPUTER SYSTEMS
Contents
Introduction iv
Types of Computer System Featured on the DVD 1
Hardware Devices 3
Types of Input Device Featured on the DVD 4
Types of Output Device Featured on the DVD 9
Types of Backing Storage Featured on the DVD 13
Questions and Tasks 19
Answers to Questions and Tasks 22
STANDARD GRADE COMPUTING STUDIESiv
COMPUTER SYSTEMS
Introduction
This publication is part of a series of publications to support Standard Grade
Arrangements in Computing Studies (March 2004). The titles in the series are:
• General Purpose Packages
• Communications and Networks
• Computer Systems
• Automated Systems
• Commercial Data Processing.
The first two packs, General Purpose Packages and Communications and
Networks, provide complete coverage of the content as specified in the updated
arrangements for Standard Grade Computing Studies.
The other three packs, Computer Systems, Automated Systems, and Commercial
Data Processing have been produced to support the three programmes featured
on the DVD. The content of these materials has been written to relate directly
to the programmes on the DVD and may not cover all the content as specified
in the course arrangements.
Computer Systems
The materials contained in this pack support the programme on the DVD
entitled The Kickin’ Technology Top 20. The materials describe a number of
items of hardware associated with input, output and backing storage devices.
The materials cover the following content as specified in the course
arrangements.
v
STANDARD GRADE COMPUTING STUDIES
COMPUTER SYSTEMS
Computer Systems – Content Covered In Support Materials
Main aspect F/G/C G/C C
Operating
•sequential and
systems
random/direct
access to data
Low-level
•megabyte (MB),
machine
gigabyte (GB)
Hardware
•backing storage •capacity of
backing storage
•desktop,•mainframe •sequential and
laptop/notebook,random/direct
palmtop access devices
•current input devices
•current output devices
•current backing
storage devices
input devices
•mouse • digital still camera •use of a variety of
(Computer
•trackpad •digital video camera input devices for
Systems)
•graphics tablet •webcam multimedia
•touch-sensitive screen •microphone
•sound card
•keyboard
output devices
•printer:Comparison of •use of variety of
(Computer
– laser Printers in terms of:output devices
Systems)
– inkjet – speed (ppm) for multimedia
•monitor (VDU) – capital costs •sound card
– running costs •graphics card
– resolution (dpi)
•liquid-crystal
display (LCD)
•thin film
transistor (TFT)
•loudspeakers
Backing storage
•magnetic tape
(Computer
•floppy disk
Systems)
•CD-ROM
•DVD-ROM
•CD-Recordable
(CD-R)
•CD-Rewriteable
(CD-RW)
•DVD-Recordable
(DVD-/
+
R)
•DVD-Rewriteable
(DVD-/
+
RW)

USB Flash Drive
•Comparison of
backing storage in
terms of:
– speed
(data transfer)
– cost capacity
STANDARD GRADE COMPUTING STUDIESvi
COMPUTER SYSTEMS
1
STANDARD GRADE COMPUTING STUDIES
COMPUTER SYSTEMS
Types of Computer System Featured on
the DVD
Mainframe
A mainframe computer is a
computer system with:
• very powerful processors
• lots of backing storage
• large internal memory.
Mainframes are designed to
process large volumes of data
at high speed. They are used
by large businesses such as
banks and mail-order
companies as well as by large
organisations such as universities.
Personal computer
A personal computer (PC) is a computer that is small and cheap enough to be
owned and/or used by a single person.
Desktop
A desktop computer is the most common kind of PC. It is a collection of a
number of different hardware devices. This type of computer is sited
permanently on a desk because its design means it cannot be easily moved.
The common components of a desktop PC are:
• the system unit containing the
processor and main memory
• monitor
• keyboard
• mouse
• hard disk drive
• floppy disk drive
• CD/DVD drive
• speakers.
STANDARD GRADE COMPUTING STUDIES2
COMPUTER SYSTEMS
Laptop/notebook
A laptop computer is a small, light computer that you can easily carry about
with you. It can be powered by battery or mains power. A laptop computer
has a keyboard, and comes with specialised input devices, for example
trackballs, touchpads or trackpoints. They are needed because laptop
computers are often operated in places where it is impracticable to use a mouse.
For output the laptop has an
LCD or TFT screen and a
set of small speakers.
‘Laptops’ are often as
powerful as desktop
computers and run the same
range and type of software.
People use laptops for
working when they are on
the move, going to meetings
or attending courses.
Many businesses are replacing desktop PCs with special plug-in workstations
designed round laptop computers because of the flexibility they offer.
Palmtop (or PDA) computer
This type of computer is increasing
in popularity, and is often called a
Personal Digital Assistant (PDA).
A palmtop computer is small
enough to fit in your pocket.
It combines a lot of capabilities,
including organiser features (such
as storing contact numbers, names
and addresses, etc.), e-mail and
wireless internet access.
Palmtops have small keyboards and most let you open menus and select icons
by using a special pen or stylus. Most let you enter data by writing with the
stylus. They are powered by batteries and store their data on removable
memory units called flash cards.
3
STANDARD GRADE COMPUTING STUDIES
COMPUTER SYSTEMS
You can run a wide range of software on palmtops, for example simple word
processing, database and spreadsheet software as well as useful applications
such as electronic diaries. Many modern palmtops:
• are converging with mobile phones to let you access the internet
• have wireless communications to let you access your local area network.
Hardware Devices
There are three categories of device that can be attached to computers we need
to know about:
• input devices
• output devices
• backing storage devices.
The use of input devices and output devices are quite obvious – giving
computers instructions and displaying results. Backing storage is the permanent
record of work completed. Files or programs saved to these devices can be
loaded later.
Input devices
A large number of different devices are to allow users to give information, or
input, to the computer. Text, numbers, sound, graphics, video, movement,
heat, touch, etc., can all be entered using the correct device.
Output devices
Output is usually limited to text, sound and pictures. Permanent paper copies
are produced using printers and plotters.
Printers use different technologies to produce paper hard copies (printouts).
Backing storage
In recent years backing storage devices have increased dramatically in their
variety and also the amount (capacity) of storage. This has dramatically
reduced the cost of storage per gigabyte
1
of information.
1
Gigabyte: a unit of information equal to one billion (1,073,741,824) bytes or 1024 megabytes
STANDARD GRADE COMPUTING STUDIES4
COMPUTER SYSTEMS
Types of Input Device Featured on the DVD
Trackpad
Trackpads are found on laptops. The trackpad does the job of the mouse and
lets you:
• control the cursor by dragging your finger across the pad
• select items from menus or open up files by tapping on the pad.
Keyboard
This is the main input device for desktop and laptop systems.
It has keys for:
• text entry
• entering numbers
• carrying out special functions such as printing the screen display.
5
STANDARD GRADE COMPUTING STUDIES
COMPUTER SYSTEMS
Mouse and trackball
A mouse is the other standard input device supplied with desktop computers.
It is a pointing device that allows the user to move a pointer or cursor across a
monitor screen. The mouse is a very important input device. It helps you to
do many things, such as:
• controlling the cursor or pointer
• opening up menus
• selecting items from menus by clicking the mouse button
• opening up software by clicking the mouse button
• dragging icons to move them into folders, to save files.
Recent changes to improve the functionality of ‘mice’ include cordless mice,
optical mice, scroll wheels and extra buttons.
A trackball is like an upside-down mouse. Instead of moving the mouse round
the desk you move the ball you can see in the picture.
Trackballs were commonly found on laptop or notebook computers, but they
are sometimes replaced with mini-joysticks and trackpads.
Graphics tablet
This has a flat surface that can sense the slightest touch. Artists and designers
use it to enter drawings into a computer system. By dragging a stylus across the
tablet surface you can draw freehand and the drawing is entered exactly into
the computer’s memory.
STANDARD GRADE COMPUTING STUDIES6
COMPUTER SYSTEMS
Digital still camera
How does it work?
1.A digital camera takes a photograph by using sensors to capture the light
that comes in through the lens.
2.It then converts the light into binary numbers that are recorded on
backing storage.
3.This digital version of the photograph can then be displayed on the small
screen that is set into the camera.
4.A digital camera also has software that lets you delete unwanted photos
while they are still stored in the camera.
5.You can connect your camera to your PC and transfer your photos across.
6.Once they are in the PC you can edit your photos further by using a
good graphics package.
What are the key features to look out for in a digital camera?
• The number of megapixels the camera has.
A megapixel is a million pixels. This is a measure of how accurately the
camera captures images. It refers to the number of sensors the camera
uses to detect the light. The more pixels, the better the quality of pictures
the camera can take.
• The amount of onboard memory the camera has.
• The larger the onboard memory the more photos it can store. Camera
memory sticks come in various sizes.
7
STANDARD GRADE COMPUTING STUDIES
COMPUTER SYSTEMS
Advantages of a digital camera
• It can hold lots of photos without the need to buy film.
• You can see what your photo is like straight away and you can delete any
you do not want.
• The photos are digital so you can transfer them to your PC and then do
all sorts of things with them such as edit, print, store on a writeable CD,
attach to an e-mail.
• You do not need to have photos developed, saving time and money.
Digital video camera
How does it work?
A digital video camera captures moving images using technology similar to
that used by a still digital camera.
• It uses light sensors to capture the images.
• The images are then changed into binary numbers.
• The binary numbers are then stored in files on the camera’s backing
storage.
What are the key features of a video camera?
The accuracy of the image sensors used to take the film. This is measured by
the number of pixels that the camera uses to capture the images.
Backing storage
This varies in size and type. Some of the latest types use DVDs to store their
video files. They can hold up to two hours of video each or over 2000 still
photos. Once filming is complete the DVD can be viewed in a DVD player or
transferred to a PC for editing.
The type of display screen available on the camera
Some have small touch-sensitive screens that allow you to make selections and
edit your film. Others have small eyepieces that you hold up to your eye to
view what you have just filmed.
Touch-sensitive screens are display screens that are sensitive to the touch of a
finger or stylus. They are often used with custom-designed applications so that
the on-screen buttons are large enough to be pressed with the finger.
Applications are typically very specialised and greatly simplified so they can be
used by anyone. However, touch-sensitive screens are also very popular on
Personal Digital Assistants (PDAs) and full-sized computers with standard
applications, where a stylus is required for precise interaction with screen objects.
STANDARD GRADE COMPUTING STUDIES8
COMPUTER SYSTEMS
The onboard editing features
The software that comes with the camera can be quite powerful offering the
user a whole range of features such as:
• focus
• adjustable lighting
• infrared
• zoom
• special effects.
Webcam
This is a digital camera that is used to take photos and then send them across
the internet. Webcams capture and transmit still photographs that can be
updated at various speeds, from one frame every few minutes, to full
streaming video, depending on the speed of the computer system and the
software settings.
The technology for capturing the images is similar to that used in the other
digital cameras.
The difference is that once an image is captured it is transmitted automatically
to a computer system. Webcam software in the computer system then transfers
it to a web page.
What are webcams used for?
They are used for a wide range of
purposes; some examples are to:
• set up videoconferencing
• monitor traffic
• advertise tourist sites
• advertise businesses.
9
STANDARD GRADE COMPUTING STUDIES
COMPUTER SYSTEMS
Types of Output Device Featured on the DVD
Printer
Computers were supposed to bring about the dream of a ‘paperless office’.
This now looks very unlikely to happen because paper has got some
advantages over computers when looking at information.
• It is very portable. The information on a sheet of paper is easily passed
around, and many people can look at the information at the same time.
• It is cheap. Initial costs of computers means there is no comparison with
the cost of using paper.
• Not everyone has computer equipment to view information, or it may
be difficult to use computers in some situations.
Paper copies, or hard copies, of information will always be needed. Printers
(and plotters) are used to produce these hard copies. The main different types
of printer, and how they are compared against each other, are explained below.
Laser printer
This type of printer is the main one used in schools, offices and industry
because it produces high-quality printouts very quickly, with good resolution.
It uses a laser to make a negative electrical image of the page on a positively
charged drum, which then picks up positively charged toner. The drum rolls
over the paper and the toner is heated to print on to the page. The toner
cartridge gives many copies before needing replaced keeping running costs down.
While it is the most expensive to buy, especially for colour, the price of this
printer has fallen dramatically.
Laser printers are generally more expensive than inkjet printers, but their
running costs are lower.
STANDARD GRADE COMPUTING STUDIES10
COMPUTER SYSTEMS
Inkjet printer
Basic models of this type of printer are cheap to buy, and let you print in colour.
The quality of the best inkjets can be very high and can be used for photographs.
Inkjet printers spray special ink on the paper to form characters and graphics.
The cost of replacing ink cartridges can be high with this type of printer
because they need replaced frequently. They print quite quickly, but can be
quite slow when printing graphics.
They are slower than laser printers.
Comparing printers
When we compare printers we should look at the following characteristics.
••
••

Set-up costsSet-up costs
Set-up costsSet-up costs
Set-up costs
This is a little tricky because it seems at first that inkjet printers are really
cheap. The initial cost or capital cost can be very low with a new inkjet
printer costing as little as £60. This is not the whole story because inkjets
can have expensive running costs.
••
••

Running costsRunning costs
Running costsRunning costs
Running costs
After you buy a printer these other costs become important.
‘Consumables’ (ink refills, toner for laser printers, special paper) need to
be bought regularly and the cost of these vary from printer to printer.
Colour inkjet cartridges can be very expensive at around £20 each.
Depending on how much printing you do you can soon end up paying
more for the ink than the printer itself!
The cost of repairs may also need to be considered for expensive printers.
••
••

ResolutionResolution
ResolutionResolution
Resolution
Resolution is measured in dots per inch (shortened to dpi). This is used
to measure the quality of the printout. Let us take the example of a
resolution of 300 dots per inch. That means that for each square inch
there are 300 x 300 dots = 90,000 dots. The higher the number of dots
per inch the sharper and clearer the image will be.
••
••

SpeedSpeed
SpeedSpeed
Speed
We should look at how long they take to print a page. Different printers
have different printing speeds. Measured in ‘pages per minute’ (ppm),
faster printers are normally more expensive and are often networked to
allow many users to take advantage of the speed.
11
STANDARD GRADE COMPUTING STUDIES
COMPUTER SYSTEMS
Comparison table
Printer Set-up cost Running cost Speed Resolution
Laser High Low Fast High
Colour laser Very high High Fast High
Inkjet Low High Quite fast Very high
LCD (liquid-crystal display)
These screens are flat, need only a small amount of power to run and can be
powered by batteries. They do not weigh as much as ordinary monitors. This
means they are ideal for use on laptops and palmtops. Liquid crystals work by
blocking light reflected from behind, so the screens cannot be read in the dark
unless they are backlit.
TFT (thin-film transistor)
TFT is a type of LCD screen that has more complex electronics than an
ordinary passive LCD. It uses arrays of transistors to control backlighting of the
screen actively. These enable it to display graphics and animations much more
clearly and quickly than an ordinary LCD and can display moving graphics
without ‘shadowing’.
Sound card
A sound card captures sounds and changes them into digital form: patterns of
binary numbers that are stored as files in your computer.
When outputting sounds the sound card reverses the process and changes the
binary data held in the sound files into analogue signals that are used to
control the speakers attached to the computer. Speakers convert analogue
audio signals into the equivalent air vibrations in order to make audible
sound. A pair of speakers plugs into the computer’s sound card.
STANDARD GRADE COMPUTING STUDIES12
COMPUTER SYSTEMS
More about capturing sound files
A microphone can be used to input sound. It converts sound waves into
analogue electrical waves. Usually called a ‘mike’, it contains a flexible
diaphragm composed of film or foil that vibrates as it makes contact with the sound.
When capturing music, for example, a sound card takes thousands of samples
of the sound waves each second, turns the samples into patterns of binary
numbers and then stores them in files.
The process of taking thousands of samples and turning them into binary
numbers is very demanding on the main processor.
For example, if a system is sampling at the standard rate of 44.1 Khz and
each sample is stored as a 16-bit binary number then the processor has to
convert and store 441,000 16-bit binary numbers each second.
To make it easier for the system, a sound card has its own processor that
relieves the computer’s main processor of all of this extra work, which would
slow it down.
Graphics card
Today’s applications use a lot of graphics. Even standard applications such as
spreadsheets run on operating systems with a WIMP HCI. This means that
all applications need graphical items to run, such as windows, icons, and
drop-down menus.
We also use multimedia and
presentation software that
incorporate graphics, animations
and even video.
Gaming software makes the
heaviest demands on the graphics
facilities of our computers with its
use of three-dimensional graphics
and realistic animations.
Graphics cards are designed to
support the need for increasingly complex graphics. Like sound cards,
graphics cards have their own processor dedicated to producing the graphics
and relieving the main system processor of the job.
13
STANDARD GRADE COMPUTING STUDIES
COMPUTER SYSTEMS
Graphics cards also have their own memory dedicated to handling the
graphic data, relieving the pressure on the system’s main memory. The
processor loads in the graphic file, which is made up of binary numbers and
then outputs the graphic as a stream of signals to control the output on the monitor.
Types of Backing Storage Featured
on the DVD
Backing storage devices are hardware that is used to store the programs and
data that the computer can access. Unlike RAM (or working) memory the
contents of backing storage will not be lost when power to the computer
system is turned off.
The three types of backing storage hardware we need to know are:
••
••

magneti c dri vemagneti c dri ve
magneti c dri vemagneti c dri ve
magneti c dri ve
– hard disk drive
– floppy disk drive
– magnetic tape drive
••
••

opti cal dri veopti cal dri ve
opti cal dri veopti cal dri ve
opti cal dri ve
– CD drive (ROM and RW)
– DVD drive (ROM and RW)
••
••

flash driveflash drive
flash driveflash drive
flash drive
Hard disk drive
This is a type of magnetic backing storage. This means, as with a floppy disk
drive, it uses magnetism to encode and store data. Hard drives consist of stacks
of non-removable platters coated with magnetic materials – each with its own
read/write head. Hard disk drives are built into desktops and laptops.
STANDARD GRADE COMPUTING STUDIES14
COMPUTER SYSTEMS
The key features of hard disk drives are:
• They read and write data very quickly.
• They can hold large quantities of data.
The capacity of a hard disk is measured in gigabytes. It holds much
more data than a CD-ROM. The capacity of a CD-ROM is measured in
megabytes. To find the capacity of the latest hard drive you should look
in the latest computer magazines or search the internet.
Hard disk drives use random/direct access to locate data stored on the disk.
Magnetic tape drive
This storage device is mostly used for backups because, although tape can store
a lot of data, it is slower to access. Having to wind through the tape when
finding files, would make it impracticable to use as the main storage device.
CD and DVD drives
Most software is now supplied on optical media such as CD-ROMs or DVD-ROMs.
CD-ROM
CD-ROM stands for: Compact Disk Read-Only Memory.
CD-ROM drives use a combination of lasers and sensors to read the data
stored on the surface of the disks. Like hard disk drives they use direct/random
access to read data.
CD-ROMs are read-only devices. They can hold in the region of 700
megabytes of data.
DVD-ROM
DVD-ROM stands for Digital
Versatile Disk Read Only
Memory
A DVD-ROM drive is similar
to a CD-ROM drive in that it
uses a combination of lasers and
sensors to read the data. DVD-
ROMs are also read only.
15
STANDARD GRADE COMPUTING STUDIES
COMPUTER SYSTEMS
How are they different?
A DVD-ROM can store much more data than a CD-ROM. A single-sided
single-layer DVD-ROM can hold 4.7 gigabytes. There are double-sided DVD-
ROMs with several layers that can store up to 17 gigabytes.
What are they used for?
DVDs are mainly used for storing movies because the files needed to encode a
movie are very large indeed and are measured in gigabytes.
CD-Recordable (CD-R)
This is a CD similar to a CD-ROM. The difference is you can store data on
the CD-R. Standard CD-R disks hold 700 megabytes.
Using a laser and special dye in the disk a CD-Rewriter drive can store your
data on the CD. Once the data has been burned on to the disk you cannot
change it, it is read only.
CD-Rewriteable (CD-RW)
Like CD-R, these are compact disks on which you can store data using a CD-
Rewriter drive. The main difference is that you can change the data later on if
you want to, just as you can on a hard disk.
STANDARD GRADE COMPUTING STUDIES16
COMPUTER SYSTEMS
DVD-Recordable (DVD-R/DVD
+
R)
2
These are DVD disks that you can write to by using a DVD-Rewriter drive.
DVD-Rewriteable (DVD-RW/DVD
+
RW)
These are DVD disks that you can store data on over and over again, with a
DVD-Rewriter drive. They use similar laser technology to CD-RW whereby
the reflective properties of the disk are altered to represent binary numbers.
DVD capacity
• Single-sided/single-layer:4.7 gigabytes of data – over 2 hours of video
• Single-sided/dual-layer:8.5 gigabytes of data – about 4 hours of video
• Double-sided/single-layer:9.4 gigabytes of data – about 4.5 hours of video
• Double-sided/mixed-layer:13.24 gigabytes of data – about 6.5 hours of video
• Double-sided/dual-layer:17 gigabytes of data – over 8 hours of video
USB backing storage devices
There is now a wide range of new storage devices that plug straight into the
USB port on computers. They can store from 8 MB up to (currently) 2 GB of
data, and are a simple and convenient way of backing up or transferring data.
Comparison of backing storage
The table below compares the storage capacity, access speed, portability and
media cost of different types of drive.
Drive Capacity Transfer Portable Drive cost Media cost
speed
Floppy Low Slow

Very low Very low
disk
Hard disk Very high Very fast Low/medium NA
Tape Very high Fast

High High
CD High Fast

Low
-
R Very low
-
RW Low
DVD Very high Fast

Low/medium
-
/
+
R Low
-
/
+
RW Low
USB High Fast

Low/medium NA
Flash
2
DVD-R[W] and DVD+R[W] are slightly different formats, but most new DVD-Rewriter drives can
handle both types.

17
STANDARD GRADE COMPUTING STUDIES
COMPUTER SYSTEMS
This table features typical information from 2004 about actual drives. You can
use it to compare how prices, sizes and rates improve over time.
Drive Capacity Transfer speed Drive cost Media cost
Floppy disk 1.4 MB 0.04 Mbps £5 10p a disk
Hard disk 100 GB 100 Mbps £50 NA
Approx 60000 2500 x FDD
FDs
Tape 30 GB 10 Mbps £370 £50
Approx 20000 250 x FDD
FDs
CD-RW 700 MB 30 Mbps £25 -R 13p
Approx 500 750 x FDD -RW 40p
FDs
DVD-RW 9 GB 30 Mbps £70 -/
+
R £1.50
Approx 6300 750 x FDD -/
+
RW £2.50
FDs
Flash 256 MB 1 Mbps £45 NA
Approx 200 25 x FDD
FDs
MB = Megabytes
GB = Gigabytes
Mbps= Megabits per second
R = Recordable
RW = Rewriteable
FD = Floppy disks
FDD= Floppy disk drive
STANDARD GRADE COMPUTING STUDIES18
COMPUTER SYSTEMS
Sequential access to data
Sequential access means starting at the beginning of a sequence of data and
going through it one part after another until the computer finds the data it is
looking for.
A magnetic tape drive, often used for backing storage, is the best example of
sequential access. It starts at the beginning of a tape and has to wind forward
through the tape until it reaches the part it needs.
This takes time and is not suitable for many computer applications that
demand fast access to data.
Random or direct access
Hard disk drives, floppy drives, CD-ROM and DVD drives use direct or
random access. This means they go straight to the data they need. Unlike
sequential access tape drives, they do not have to go through all of the disk
surface one part after another to find the data.
Because it gives instant
access to the data, direct or
random access is used by
computer systems that need
to process data straight
away, unlike sequential
access, which takes time to
go through all the data in
the sequence.
Examples of use: updating
bank accounts as money is
taken out of a cash point
machine, booking seats on
a plane.
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STANDARD GRADE COMPUTING STUDIES
COMPUTER SYSTEMS
Questions and Tasks
1.Why do large businesses such as banks use mainframe computers?
2.Describe the components of the desktop computer you use in school or
at home.
3.Complete this table comparing a desktop with a laptop.
Desktop Laptop
Output Ordinary monitor LCD/TFT
Backing storage Hard disk, floppy disk,
CD/DVD drive
Power source Mains power
Portable No
4.Name three types of software that run on palmtops.
5.Why are palmtops useful?
6.What is the typical capacity of a CD-ROM?
7.What are CD-ROMs used for?
8.What is the typical capacity of a DVD-ROM?
9.Why are DVD-ROMs used to store videos?
10.(a) What do CD-R and DVD-/
+
R have in common?
(b) In what way are they different?
11.(a) What do DVD-/
+
RW and CD-RW have in common?
(b) In what way are they different?
12.Complete this table comparing laser printers to inkjet printers. You may
have to search the internet to find out the relevant information.
STANDARD GRADE COMPUTING STUDIES20
COMPUTER SYSTEMS
Printer Laser or Resolution Speed Initial Cost of the
make/model inkjet (dpi) (ppm) purchase ink/toner
cost
HP deskjet Inkjet 4800 x 7 ppm £260 2.65 pence per
9300 1200 dpi mono page
7.1 pence per
colour page
Epson Colour 600 x 600 16 ppm £679 1.5 pence per
Aculaser laser mono page
C900 6.7 pence per
colour page
Inkjet
Laser
Inkjet
Laser
13.What is the difference between an LCD screen and a TFT screen?
14.What features of LCD/TFT screens make them suitable for use on laptops?
15.Why is a trackpad suitable for controlling the pointer on a laptop?
16.Why do you think the combination of a keyboard and mouse is used as
a means of inputting data into a desktop?
17.Describe a graphics tablet.
18.Who uses a graphics tablet?
19.How does a digital still camera work?
20.List four advantages of digital cameras.
21.Use the internet or the latest magazines to get information on four of the
latest digital cameras and then complete the following table.
Name and Memory Number of Editing
make of capacity megapixels features
camera
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STANDARD GRADE COMPUTING STUDIES
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22.How does the storage capacity of a digital video camera different from
that of a digital still camera?
23.In what way is a digital video camera the same as a digital still camera?
24.How does a webcam operate?
25.Use a search engine to find a list of webcam sites and check some out for
yourself, then complete the following table.
Webcam address Webcam used for:
www.
26.What is the difference between sequential and random/direct access to data?
27.Which types of backing storage uses random/direct access to data?
28.How does a sound card capture sounds?
29.Search for two sound cards on the internet or in a computing magazine
and write up a short report on each one.
30.Why do computers need graphics cards?
31.Why do graphics cards have their own processor and memory?
32.Use the internet to search for graphics cards. Pick two and write a short
report on their main features.
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COMPUTER SYSTEMS
Answers to Questions and Tasks
1.Because they:
• have very powerful processors
• have a large amount of backing storage
• are designed to process large volumes of data at high speeds.
2.Mention the monitor, the processor, the memory and backing storage as
well as any peripherals attached to it.
3.
Desktop Laptop
Output Ordinary monitor LCD/TFT
Backing storage Hard drive, CD/DVD Possibly all three,
drive depending on the model
you chose
Power source Mains power Main or battery
Portable No Yes
4.Simple word processing, database and spreadsheet software as well as
useful applications such as electronic mail.
5.Because they are compact and can fit in your pocket. They can run a
range of software and the latest versions enable you to access the internet
and connect with your LAN.
6.700 megabytes
7.Storing large files that do not need to be updated, for example
encyclopaedias, software, games.
8.A single-sided DVD will hold 4.7 gigabytes. A double-sided double-
layered DVD will hold four times that amount.
9.Because of their large capacities.
10.(a) You can write data to them once. They both use laser technology.
(b) DVDs have a much higher capacity.
11.(a) You can write data to them over and over again. They both use
laser technology.
(b) DVDs have a much higher capacity.
12.Completed table comparing laser printers to inkjet printers.
13.A TFT screen uses more complex electronics, an array of transistors, to
control backlighting of the screen. The result is that it gives a clearer
image than an ordinary LCD screen and displays moving graphics
without ‘shadowing’.
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COMPUTER SYSTEMS
14.They are compact and light.
15.Because you can operate it without the need for a mouse or a flat surface
like a desk. This makes it ideal when you are on the move.
16.Because they complement each other. The keyboard is used to enter text
and keyboard shortcuts. The mouse is used to control the pointer and
select icons and items on menus.
17.It has a flat surface that can sense the slightest movement. Artists and
designers use it to enter drawings into a computer system. By dragging a
stylus across the tablet surface you can draw freehand and the drawing is
entered exactly into the computer’s memory.
18.An artist or designer who needed to enter freehand drawings.
19.A digital camera takes photographs by using sensors to capture the light
that comes in through the lens. It then converts the light into binary
numbers that are recorded on backing storage. This digital version of the
photograph can then be displayed on the small screen that is set into the camera.
20.• They can hold lots of photos without the need to buy film.
• You can see what your photo is like straight away and you can delete
any you do not want.
• The photos are digital so you can transfer them to your PC and then
do all sorts of things with them such as: edit them, print them, store
them on a writeable CD, attach them to an e-mail.
• You do not need to have them developed, saving time and money.
21.Completed table with name and make of camera, memory capacity,
number of megapixels and any editing features.
22.They tend to have much larger storage capacities because of the size of
the video files.
23.They both operate in basically the same way.
(a) They use light sensors to capture the images.
(b) The images are then changed into binary numbers.
(c) The binary numbers are then recorded in files on the cameras
backing storage.
24.A webcam uses technology for capturing the images that is similar to that
used in the other digital cameras. Webcams are used to take photos and
then send them across the internet. Webcams transmit photographs that
are regularly updated at various speeds from one every few minutes to
full streaming video.
25.List of webcam sites with a description of what the webcam is used for.
STANDARD GRADE COMPUTING STUDIES24
COMPUTER SYSTEMS
26.Sequential access to data involves the system going through blocks of
data one after another, in turn, before accessing the item of data required.
Using random/direct access a system can go directly to the data required.
27.Hard disks, floppy disks, CD-ROMs, CD-R, CD-RW and all DVDs
28.It takes thousands of samples of the sound waves each second, turns the
samples into patterns of binary numbers and then stores them in files.
29.The answer to this will depend on the result of your search.
30.Because the latest software uses increasingly complex graphics, including
3-D graphics and animations.
31.They need their own onboard processor to relieve the main processor of
the burden of handling all the graphics. Similarly, they need lots of
onboard, dedicated memory to free the computer’s main memory of
the need to store the very large graphics files that are being processed.
32.The answer to this will depend on the results of your internet search.
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STANDARD GRADE COMPUTING STUDIES26
COMPUTER SYSTEMS