Computer Science Study Guide

End of Term Exam

Academic Session 2023 – 24

Student’s Name:
Class: VII Teacher’s Name: Arif Hussain

Note:

Please note that this Study Guide has been devised for revision
as an additional resource pack for the learners’ reference and
further support along with all the revision activities conducted at
school. This guide has been designed as a compilation of reference
material from Curriculum objectives & some tasks for practice to
supplement students’ learning.
The students can use this study guide at their own pace and
convenience, however, if there are any questions about using the
resource pack or would like additional support related to the
concepts provided, please do reach out to the teachers. Please note
that we will be referring to the study guide in class as well.
We wish Good luck to all our learners for the Exam Preparation and
thank parents & teachers for their continued partnership and
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 support.

Topics

Chapter 1: Types and Components of Computer

Chapter 2: Input and Output Devices
Chapter 3: Storage Devices and media
Chapter 9: Audiences
Chapter 2: Data Transmission (CS Book)

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 Chapter 1: Types and components of computer systems

Augmented Reality:

Virtual Reality:

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CPU

CPU The central processing unit (CPU) is the part of the computer that interprets and executes the commands
from the computer hardware and software. It is normally part of the computer motherboard

RAM and ROM

Input and output devices

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Backing storage
The main memories in a computer are RAM and ROM. However, to permanently store large amounts of data it
is necessary to use backing storage. This normally takes the form of the internal hard disk drive (HDD) or solid-
state drive (SSD).

Operating System:
To enable computer systems to function and to allow users to communicate with computer systems, special
software, known as operating systems (OS), have been developed. The general tasks for a typical operating
system include: » control of the operation of the input, output and backing storage devices » supervising the
loading, running and storage of applications programs.

User interfaces
Operating systems offer various types of user interface. We will consider four different types:

» command line interface (CLI)

» graphical user interface (GUI)

» dialogue-based user interface

» gesture-based user interface.

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WIMP:
GUIs use various technologies and devices to provide the user interface. One of the most common is WIMP
(windows icons menu and pointing device) which was developed for use on personal computers (PC). Here, a
mouse is used to control a cursor and icons are selected to open/run windows.

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 Activity

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 Marking Scheme

4.

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 Chapter 2: Input and Output Devices

Input Devices:
These are hardware devices that allow data to be input into a computer such as the keyboard, through to
more specialist devices, such as barcode readers.

Keyboards

Keyboards are by far the most common method used for

data entry. They are used as the input device on computers,
tablets, mobile phones and many other electronic items.

Advantages of keyboards
» Fast entry of new text into a document.

» Well-known method.

» Easy to use for most people.

Disadvantages of keyboards

» Can be difficult to use if the user has limited arm/wrist use.

» Fairly large device that uses up valuable desk space

Pointing devices

Mouse
The mouse is an example of a pointing device. The user controls the position

of a pointer on the screen by moving the mouse around.

Advantages of a mouse

» Faster method for choosing an option rather than using a keyboard.

» Very quick way of navigating through applications and the interne

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Disadvantages of a mouse
» Can be more difficult for people with restricted hand/wrist movement than using a keyboard for data
entry.
» Easy to damage, and the older type of mouse quickly becomes clogged up with dirt.

Trackerball
Trackerballs are similar to a mouse, except that a ball is on the top or the side of the device; the user
controls the pointer on the screen by rotating the ball with their hand.

Touch screens (as an input device)

With a touch screen the user can choose an option by simply touching a button/icon on the screen. The
selection is automatically made without the need for any pointing device.

Advantages of touch screens

» Faster entry of options than using keyboard or mouse.

» Very easy method for choosing options.

» User-friendly method – no training necessary in its use.

» Option to expand the size of the display if necessary.

Disadvantages of touch screens

» Limited number of input options available.

» Can lead to problems if an operator has to use the system frequently (straining of arm muscles, RSI, etc.
are all possible).

Scanners

Scanners are used to enter information from hard copy (for example, text documents, photographs) into a
computer. The most common type is the flatbed scanner.

Microphones

Microphones are either built into the computer or are external devices connected through the USB port or
using Bluetooth connectivity.

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Sensors

A sensor is a device that inputs data to a computer; the data is a measurement of some physical quantity that
is continuously changing (for example, temperature, light, moisture, etc.). These physical quantities are
analogue in nature. Because computers only understand digital data (1s and 0s), the information from the
sensors needs to be converted; this is done using an analogue to digital converter (ADC).

Direct data entry (DDE)

devices are used to input data into a computer without the need for very much, if any, human interaction. For
example, barcode readers are DDE and the only human involvement is to point a reader at the barcode.

Magnetic stripe readers

These are used to read information on the magnetic stripe found on, for example, the back of a credit or debit
card.

Advantages of magnetic stripe readers

» Fast data entry, rather than keying in with a keyboard or keypad.

» Error-free (because no typing is involved).

» No moving parts – so physically very robust.

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Disadvantages of magnetic stripe readers
» If the magnetic stripe gets damaged (for example, due to exposure to a strong

magnetic field) the data is lost.

» Does not work at a distance (card needs to be in close contact with reader).

Chip and PIN readers

Chip and PIN readers are similar to smart card readers but are used at EFTPOS terminals. The device has a slot
into which the card is placed and the chip is read; the PIN is entered using the keypad. The reader also has a
small screen which gives instructions to the operator.

Advantages of chip and PIN readers

» More secure system than contactless payments (PIN typed in must match up

with PIN stored on chip).

» More robust system than magnetic stripe cards.

Disadvantages of chip and PIN readers

» Fraud – need to be careful to ensure PIN is not read by somebody else while

typing it in.

Radio frequency identification (RFID)

readers Radio frequency identification (RFID) readers use radio waves to read and capture information stored
on a tag. In some applications, the tag can be read from a distance of several metres, which is one of its
advantages over the barcode system. The RFID tag is made up of two components:

» a microchip that stores and processes information

» an antenna which is used to receive and transmit data/information.

Advantages of RFID

» No line-of-sight contact is necessary; the tags can be read from a distance.

» It is a very robust and reliable technology.

» Very fast read-rate (typically less than 100 milliseconds to respond).

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Disadvantages of RFID
» Tag collision (this is when the signals from two or more tags overlap,

interfering with each other).

» Because RFID uses radio waves, they are relatively easy to jam or interrupt.

Optical mark recognition/reader (OMR)

Optical mark recognition (OMR) is a device which can read marks written in pen or pencil on a form. The places
where the pen or pencil marks can be made are clearly shown on the form.

Advantages of OMR devices

» Very fast way of inputting the results of a survey, etc. The documents are fed in automatically and there
is no user input.
» Because there is no typing, they are more accurate than keying in the data.
» They are more accurate than OCR methods.

Disadvantages of OMR devices

» The forms need to be carefully designed to make sure the marks/shading are

correctly positioned to gather accurate information.

Optical character recognition/reader (OCR)

Optical character recognition (OCR) is the name given to a device that converts the text on hard copy
documents into an electronic form.

Barcode readers

Barcode readers are used to read information in the form of a bar code.

Quick response (QR) code scanners (readers)

Another type of barcode is the quick response (QR) code. This is made up of a matrix of filled-in dark squares
on a light background.

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 Output Devices

these are devices that usually show the result of computer processing in a format that can be understood by a
human (for example, on a monitor or printed on paper)

Monitors (screens)

two types of monitor:

» the cathode ray tube (CRT) monitor

» LCD (or TFT) screen (TFT means ‘thin film technology’; a general term for modern thin screens).

CRT monitors Cathode ray tube (CRT) monitors are the least expensive type of monitor, although they are
becoming increasingly rare as LCD monitors are now taking over.

LED and LCD screens

LED screens

An LED screen is made up of tiny light emitting diodes (LEDs). Each LED is either red, green or blue in
colour. By varying the electric current sent to each LED, its brightness can be controlled, producing a vast
range of colours.

Multimedia projectors

Multimedia projectors receive signals that can be either analogue or digital (although most modern projectors
only work with digital inputs). The signal source is usually from a computer, television or DVD player. The
image from the source is magnified and projected onto a large screen.

Printers

three most common types of printer:

» laser printer

» inkjet printer

» dot matrix printer

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Laser printers

Laser printers produce very high-quality hard copy output. The print rate per page is very quick if a large
number of pages are being printed.

Dot matrix printers

Dot matrix printers are a type of impact printer where a print head (made up of a matrix of pins) presses
against an inked ribbon. They tend to be slow, noisy and the output is not that good compared to inkjet and
laser printers.

3D printers

3D printers are primarily used in computer-aided design (CAD) applications. They are primarily based on inkjet
and laser printer technology and can produce solid objects that actually work. The solid object is built up layer
by layer using materials such as powdered resin, powdered metal, paper or ceramic.

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Speakers:

Actuators
When a computer is used to control devices, such as a conveyer belt or a valve, it is usually necessary to use an
actuator to, for example, start/stop the conveyer belt or open/close the valve. An actuator is a mechanical or
electromechanical device such as a relay, solenoid or motor.

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 Activity

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 Marking Scheme

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 Chapter 3: Storage Device and media

Magnetic tape drives:

Hard disk:

Hard disk drives (HDD) are still one of the most common methods used to
store data on a computer. Data is stored in a digital format on the magnetic
surfaces of the hard disks (or platters, as they are usually called). A hard disk
drive will very often have more than one platter depending on its capacity.

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Optical media

Solid-state drives
(SSD) Uses of SSDs Solid-state drives have revolutionised computers over the last few years, and they are
rapidly taking over from HDDs as the main type of backing storage. As the name suggests, they use solid-state
media and can be used in the same way as an HDD (that is, as a storage device to store files, applications,
operating system, and so on).

Pen drives Pen drives

(memory sticks) are small portable devices that make use of solid-state technology. They connect to the
computer through a USB port. Their main advantage is that they are very small, lightweight portable devices.

Future of Storage devices: Cloud Storage

In recent times, both the CD and DVD are showing signs of becoming obsolete. Many computer systems now
come only with USB connectors and no internal DVD or CD drive. The main method of transferring files
between devices has become the flash memory. Many people now store all their music in the following ways:
» on hard disk drive systems (set up as sound systems, as shown in Figure 3.10) » in MP3 format on: – a
computer/tablet – their mobile/smartphone – a portable music player (such as an iPod) » using the cloud to
store all their files so they can access their music from anywhere in the world » by streaming their music from

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the internet; provided the user has an internet connection, they can access music through a laptop computer,
smartphone, tablet or any other receiving device.

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 Activity

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 Marking Scheme
5.

Answer 6:

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 Chapter 9: Audiences

Audience characteristics

Who will be using the new website? First, consider the characteristics of your target audience when using the
new website:

» age range

» income levels

» interests

» disabilities or impairments.

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Needs of the audience

Once you have established the characteristics of the audience that the website is aimed at, it is necessary to
understand their specific needs in a bit more depth, to ensure the final product is fit for purpose.

Why we need to consider the needs of our audience

Why is it important to respectfully consider these needs?

» If the audience is made up of older people, or people with disabilities, who have sight problems, then it is
important to make sure the website has clearto-read fonts.

» Complex language can be a real turn off to children or for people who have English as their second language;
the text needs to be clear and easy to read for these reasons.

Software copyright and piracy

Software is protected by copyright laws in much the same way as music CDs, movies, and articles from
magazines and books are protected.

When software is supplied on CD, DVD or online there are certain rules that must be obeyed. It is illegal to:

» make a software copy and then sell it or give it away to a friend or colleague

» use software on a network or on multiple computers unless a licence has been

acquired to allow this to happen

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» use coding from the copyright software in your own software and then pass this software on or sell it as your
own without the permission of the copyright holders.

Software piracy is the illegal copying of software. It is a big issue among software companies. They take many
steps to stop the illegal copying and to stop any illegal copies being used once they have been sold.

There are a number of ways software is protected – either by making the installer agree to certain conditions
or by methods which require the original software to be present for it to work:

» When software is being installed, the user may be asked to key in a unique reference number or product key
(a string of letters and numbers) which was supplied with the original copy of the software (for example:
4a3c0efa 65ab a81e).

» The user will be asked to click ‘OK’/’I AGREE’ or put a cross in a box to agree to the licence agreement before
the software continues to install.

» If supplied as a hard copy, the original software packaging often comes with a sticker informing the
purchaser that it is illegal to make copies of the software; the label is often in the form of a hologram
indicating that this is a genuine copy.

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 Activity
1

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 Marking Scheme
1

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 Chapter 2: Data Transmission

Data packets
Data sent over long distances is usually broken up into data packets (sometimes called datagrams).

Packet switching

when a photograph is sent from computer ‘A’ to computer ‘B’. The photograph will be split up into a number
of packets before it is sent. There will be several possible routes for the packets, between computer ‘A’
(sender) and computer ‘B’ (receiver). Each stage in the route contains a router. A router receives a data packet
and, based on the information in the header, decides where to send it next.

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Packet switching
is a method of data transmission in which a message is broken up into a number of packets.

The benefits of packet switching are:

» there is no need to tie up a single communication line

» it is possible to overcome failed, busy or faulty lines by simply re-routing packets

» it is relatively easy to expand package usage

» a high data transmission rate is possible.

The drawbacks of packet switching include:

» packets can be lost and need to be re-sent

» the method is more prone to errors with real-time streaming (for example, a

live sporting event being transmitted over the internet)

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Serial data transmission works well over long distances. However, the data is transmitted at a slower rate than
parallel data transmission. Because only one channel/wire is used, data will arrive at its destination fully
synchronized.

universal serial bus (USB)

is a form of serial data transmission. USB is now the most common type of input/output port found on
computers and has led to a standardisation method for the transfer of data between devices and a computer.

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Check Digit:

An Automatic Repeat Request (ARQ)

is a third way used to check data following data transmission.

This method can best be summarized as follows:

» ARQ uses positive and negative acknowledgements (messages sent to the receiver indicating that data
has/has not been received correctly) and timeout (this is the time interval allowed to elapse before an
acknowledgement is received)

» the receiving device receives an error detection code as part of the data transmission (this is typically a Cyclic
Redundancy Check – refer to Section 2.1.1); this is used to detect whether the received data contains any
transmission errors

» if no error is detected, a positive acknowledgement is sent back to the sending device

» however, if an error is detected, the receiving device now sends a negative acknowledgement to the sending
device and requests re-transmission of the data

» a time-out is used by the sending device by waiting a pre-determined amount

of time ….

» ... and if no acknowledgement of any type has been received by the sending device within this time limit, it
automatically re-sends the data until a positive acknowledgement is received ….

» ... or until a pre-determined number of re-transmissions has taken place

» ARQ is often used by mobile phone networks to guarantee data integrity.

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Symmetric encryption
Symmetric encryption uses an encryption key; the same key is used to encrypt and decrypt the encoded
message.

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1

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1

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