Computer science

identify practical applications where BCD is used.

Any scenario where a single digit needs to be transmitted/ displayed. example: calculator

Describe how an 8-bit BCD can be converted into a denary integer.

Binary number is split into groups of 4-bits, each group of 4-bits is converted to a denary digit. example: 0011 0111 = 37

Describe how denary integers larger than 9 can be converted into BCD.

each denary digit is written as 4-bit binary numbers. example: 46 = 0100 0110

State how an overflow can occur when adding two binary integers.

The result is a larger number than can be stored in the given number of bits.

what is the representation of “A” in ASCII?

65

what is the representation of “a” in ASCII?

97

What are disadvantages of using ASCII code?

• only 128 characters can be represented

• uses value 0 to 128

• many characters used in other languages cannot be represented

• in extended ACII.

How is Unicode designed to overcome the disadvantages of ASCII.

• uses 16, 24, 32 bits.

• Unicode is designed to be a superset of ASCII.

• designed so that most characters in other languages can be represented.

How many characters can be represented in ASCII?

128

How many characters can be represented in extended ASCII?

256

what is a pixel?

• smallest picture element

what is meant by image resolution?

• measured in pixels per inch, this value determines the amount of detail a picture has

• Higher image resolution means there are more pixels per inch resulting in a higher quality image

what is meant by screen resolution?

• the number of pixels which can be viewed horizontally and vertically on the screen.

What is color depth?

• number of bits allocated to represent each pixels color.

What is Meta Data?

• data about data

What is meant by File Header?

• contains information about the file such as, number of pixels, size of the image, color depth and file location

How are images encoded into a digital format?

• The images are stored as bitmap images

• each image is made up of pixels

• each pixel is of a single color

• each color has a unique binary number

• sequence of each binary number is stored

What are features of graphic editing software?

• Re-Size: increase/decrease the size of the image

• Crop: remove certain parts of the image

• Blur: reduce the focus

• Red-eye reduction: reduces red light reflected from the human eye

What are the features of vector graphics?

• vector graphic store a set of instructions about how to draw the shape

• can be enlarged without the image being pixelated

• Does not compress well

• suitable for more geometric shapes

What are benefits of vector graphics?

• can be resized without pixelization

• images are redrawn with each adjustment

• smaller file size

• can be transferred and downloaded quick

What is a drawing list

the list of shapes involved in an image

what is digital data?

data that has been stored as a binary value.

what is analogue data?

data obtained by measurement of physical property.

what is meant by sampling?

taking measurement of sound at regular intervals.

what is meant by sampling rate?

the number of samples taken per second.

What is sampling resolution?

the number of bits used to store each sample.

how is sampling used to record sound clips?

• The amplitude of the sound wave is determined

• at set time intervals

• to get an approximation of the sound wave

• encoded as a sequence of binary numbers

• increasing the sampling rate will increase the accuracy of the recording

what are benefits of using higher sampling resolution?

• allow for large dynamic range

• more accurate representation

what are drawbacks of using high sampling resolution?

• bigger file size

• longer to transfer/download data

what are features of sound editing software?

• edit start/stop time

• delete parts of the clip

• frequency of sound can be altered

how to calculate file size?

Size = pixel width x pixel height x bit depth. (the answer is in bits)

what is lossless compression?

in this technique, the data is not lost, and the compressed file can be decompressed as the original

what is lossy compression?

in this technique, the data is lost and the decompressed data is not the same as the original

What are advantages of using network?

• File sharing: users can share files with other users

• Software Sharing: Users can share software applications

• Communication : users can send emails

What are disadvantages of using network?

• Cost: Additional equipment would be required

• Management: Network requires management

• Malware: viruses can easily spread though improperly secured networks

What is meant by network?

When two or more devices are connected through wires or wireless.

What is meant by a client-server model of network computers?

• At least one computer used to “serve”

• other computers are known as clients

• server provides services/applications

Downloading a file from a website is an example of client-server application.
Describe what is meant by the term client-server?

• The file is made available from the web server

• the users browser is the client software

• the client requests the file from the server

• the desired file is returned to the client

A bank has a client-server model of networks.
Describe using the bank as an example, the key features of a client-server model.

• The banks server holds the customer account information and performs the requested task

• the computer used by the customers are clients

• that send requests to the server

How does client-server model enable employees to access the same files from different computers?

• employees computers are clients

• the server hosts the shared file

• an employee can request a file from the server from any clients computers

• several employees can access the same file.

Benefit of client-server.

• files and resources are centralised

• creates security

• centralising back up

• internet monitoring

describe key features of peer to peer network.

• all computers are of equal status

• each computer provides access to resources and data

• each computer is responsible for its own security.

benefits of peer to peer network

• avoids the possibility of congestion when more clients simultaneously request files

• allows users to download different parts of the file separately

• the parts are available from more than one host

describe drawbacks of peer to peer

• reduced security, each computer is at risk from viruses from other computers

• no central management of back up, if the data from one computer is not backed up, it is lost to all of them

• individual computers may respond slower as they are being accessed by other computers

describe thin client.

a device or software which is heavily dependent on having access to the server, thin client will not work unless it is connected to the server.

describe thick client

a device or software that can also work offline it is still able to do some processing without being connected to the server

advantages of thick client

• More robust as client can carry out processing even when not connected to the server

• better uptime

• reduces server demand

disadvantages of thick client

• less secure

• each client needs to update data and software individually

• data integrity issues, since many clients access the same data it can lead to inconsistent data

Advantages of thin client

• less expensive to expand as low powered and cheap devices can be used

• more secure as server can offer protection from hacking

• data updates done centrally on the server

disadvantage of thin clients

• dependent on the server, if server goes down the device cant work

• more downtime

what are the differences between thin and thick clients?

• Thin client relies on server, thick client can work without the server

• thin client relies on fast internet, thick client can work on slow internet

• data for thin client is stored on the server, data for thick client is stored on the device itself

what are the advantages of a bus topology?

• easier to setup/extend

• less cable required

• less expensive

what are disadvantages of bus topology?

• difficult to detect and troubleshoot a problem at an individual station

• efficiency reduces as more devices are connected

• collisions, not suitable for networks with high traffic

how are packets transferred between two computers in a bus topology?

• packet has address of the recipient

• sender transmits data through bus

• the bus carries the data along the central cable

• as the data arrives at each computer, the system compares the address to see if it matches

where is bus topology used?

• when small and temporary networks are needed

• networks which do not rely on high transfer speeds

• used in offices or schools

what are advantages of star topology?

• signals only go to destination, so it is secure

• easy to connect/remove node

• centralised management, helps monitor network

• fewer collisions

what are disadvantages of star topology?

• if the central device fails, the whole network goes down

• performance is dependent on capacity of central device

how are packets transferred between computers in star topology?

• packets have address of recipient

• sender sends the data to central device

• sender reads the data and finds the recipient

• server directly sends the data to the recipient

where is star topology used?

• Large organisations

• educational establishments

• where high performance is a must

• found in homes aswell, where the router acts as the server

features of star topology

• must have a central device

• each node is connected to the central device

• each node has a dedicated connection

• each connection must be bi directional

what are advantages of a mesh topology?

• any broken links in the network do not affect the other nodes

• good privacy and security, since packets travel along dedicated routes

what are disadvantages of mesh topology?

• a large amount of cabling is required, which is expensive

• setup and maintenance is difficult

how are packets transmitted in mesh topology?

• packets have address of the recipient

• sender transmits data directly to node

• as each node is connected to at least another node

where is mesh topology used?

• where establishment of communication is very important

• military organisations

• emergency service

what are advantages of hybrid topology?

• highly reliable, in case of failure there are many sub networks

• easy to troubleshoot and fix errors

what are disadvantages of hybrid topology?

• expensive to set up

• difficult to manage

• complex network

where is hybrid topology used?

• large organisations with different topologies in each building

What is meant by cloud computing?

cloud computing refers to data and applications being stored and run on the cloud so less storage is occupied and less processing is done on local device

what are advantages of cloud computing?

• no need to carry external storage

• cloud storage can be free

• security could be better

• can easily increase capacity

what are Disadvantages of cloud computing?

• can only access cloud with internet access

• no control over security

• it can take a long time to upload/download data

• it can be more expensive in the long run

what is private cloud?

• Owned and only accessed by an organization

what are applications of private cloud?

• highly regulated industries and govt agencies use private cloud

what is public cloud?

• owned by a cloud service provider

what are applications of public cloud?

for general use

What are benefits of a wireless network compared to a wired network?

• devices can be more mobile as they do not need to be connected to a cable

• easier to set up as no cables need to be installed

• additional devices can easily be added

What are drawbacks of a wireless network compared to a wired network?

• easier to hack

• interference

• signal degrades quickly

types of wired connections?

• copper cable (Twisted and Co-axial cable)

• Fibre optic cable

Twisted cable

it is a copper cable copper used to connect telephones to telephone lines, one cable with 4 twisted pairs

Coaxial cable

it is a copper cable, used in long distance telephone cabling by cable television companies

Fibre optic cable

light is transferred by using the concept of total internal reflection

what are benefits of fibre optic cable?

• less interference in the signal

• faster transmission

• light in weight

drawbacks of fibre optic cable

• installation cost is high

• breaks when bent

• only transfers data in one direction

What are benefits of copper cable?

• installation cost is low

• more flexible

• easier to terminate

What are drawbacks of copper cable?

• higher interference

• less bandwidth

microwaves?

• are electromagnetic waves, frequency range 3GHZ - 300GHZ, used in TV and MRI

Radio waves?

• are electromagnetic waves, frequency range 3KHZ - 3GHZ, carry data back and forth between wireless adapter and router

infrared waves?

• are electromagnetic waves, frequency range 300GHZ - 400THZ, used in TV remote

What are the hardware used in LAN?

• Switch

• NIC (network interface card)

• WNIC (wireless network interface card)

• cables

• bridge

• WAP (wireless access point)

• repeater

describe a switch

a connecting device that can send unicast message

describe an NIC (network interface card)

• provides device with a mac address

• to uniquely identify it on the network

• allow each individual device to connect to the network

describe a WNIC (wirless network interface card)

• provides device with a mac address

• to uniquely identify it on the network

• allow each individual device to connect to the network wirelessly

describe a bridge

• connects two different LANS

• Divides a single LAN into two to reduce traffic

Describe a WAP (wireless access point)

• allowing devices to connect to the LAN

• instead of using cable

• easy to move a device to a different location

describe a repeater

• used to boost signals

what are features of a Router?

• connects two or more network

• can connect network to LAN

• Assigns private Ip Address

• connects similar networks

What are features of a gateway?

• connects two or more network

• can connect network to WAN

• Assigns private IP address

• connects dissimilar networks

what is the internet?

• massive network of networks

• uses TCP/IP protocols

• stands for interconnected networks

What is WWW (world wide web)

• is a collections of web pages/documents

• stored on website

• web pages are written in HTML

• URL specify the location of the webpages