CoSCi 2023 Past Paper THEORY

An office building has desktop computers connected in a network.

One reason for networking computers is to enable technicians to maintain

them remotely.

State two other reasons for connecting computers in a network

• Access the Internet

• Allow data/files/information to be shared

• Provide communication (email, social media, online meeting, chat)

• Provide collaboration (editing online docs)

Access to data must be controlled.

Identify one reason that encryption is used.

A To compress the file so it takes up less storage space

B To make sure both sender and receiver use the same key

C To make sure data is only understood by the intended receiver

D To stop malicious hackers getting into a computer network

The correct answer is C

A is not correct because compression does not encrypt a file

B is not correct because encryption does not ensure both sides use the same key

D is not correct because encryption does not stop hackers accessing a network

File servers are in a small room at the back of an office.

The office has a burglar alarm.

Give two other ways that the servers can be secured using physical methods

• Lock on doors

• Biometrics/ key cards

• Security guards

• Surveillance cameras

Phishing is a type of social engineering.

State what is meant by the term social engineering

manipulation technique that exploits/relies on human behaviour to trick people to reveal sensitive information

5G is a communication standard.

Identify the characteristic that is true for the 5G communication standard.

A It has a high transmission latency

B It has built-in security

C It has a lower bandwidth than 3G and 4G

D It uses wireless communication

The correct answer is D

A is not correct because 5G does not have a high transmission latency

B is not correct because a 5G does not have built-in security

C is not correct because 5G does not have a lower bandwidth than 3G and 4G

Programmers write and test code.

They use modular testing.

State what is meant by the term modular testing

Testing each block of code/subprogram/function independently (as it is written/finished)

Computer scientists are viewed as professionals, in the same way that doctors are

viewed as professionals.

Give two ways that computer scientists can demonstrate professionalism.

• Behave in ethical/legal/moral ways

• Attend computer science related conferences/gatherings

• Stay up to date with changes in the field/read up-to-date publications

• Avoid bias when making design choices

Complete the table by adding the hexadecimal notation for each of the denary values.

8 = ?

12 = ?

8 = 8

12 = C

Identify the expression to give the number of unique binary patterns that can be stored in six bits.

A 6²

B 6 × 2

C 6² – 1

D 2^6

The correct answer is D

A is not correct because 6² stores 36 patterns, not 64 patterns

B is not correct because 6 × 2 stores 12 patterns, not 64 patterns

C is not correct because 6² – 1 stores 35 patterns, not 64 patterns

Give the result of applying a logical shift right by two to the binary pattern

01011100

00010111

Give the result of applying an arithmetic shift right by three to the binary

pattern 11000101

11111000

Binary patterns can be interpreted as signed or unsigned integers.

Convert the denary unsigned integer 60 to 8-bit binary.

00111100

Here is a binary bit pattern for a signed integer in sign and magnitude format.

10010110

Convert the binary bit pattern to denary.

Be sure to include a sign symbol in your answer.

• Negative sign

• 22

-22

Negating a signed integer means changing its sign without changing

its value.

The negation of +16 is –16. The negation of –24 is +24.

Here is the binary bit pattern for a signed integer in two’s complement format.

11100101

Convert the binary pattern to its negation in two’s complement.

00011011

Construct an expression to convert 13 kilobytes to kibibytes.

1. 13 x 1000 // 13000 in the numerator (1)

2. 1024 in the denominator (1)

Examples:

13 × 1000 /1024

13000 / 1024

13 × 500 / 512

13 × 250 / 256

13 × 125 / 128

13 × 10^3 / 2^10

Software programs carry out tasks on computers.

A headteacher uses a computer simulation to model the effect of increasing class sizes.

Explain one problem with using simulations to predict the effects of changes.

• If the data is incomplete/inaccurate the answers from the model might not be right

• If the assumptions the model is based on are inaccurate the answers from the model might be incomplete/inaccurate

Images are stored as files before being displayed or printed.

Give one measurement of image resolution.

• Pixels per inch/ppi

• Pixels per centimetre/ppc

• Dots per inch/dpi

Increasing the colour depth of an image leads to an increase in the image file size.

Describe the reason for the increase in file size.

Each pixel/colour in the image will require more bits to store

Software is divided into two categories.

Describe one difference between system software and application software.

System software is used to maintain/run the operation of the system/hardware whereas application software allows the user to carry out a task

Here is part of a file that contains electric meter readings.

04631 04984 05103 05163 05271 05383 05487 05722

Explain the effect on the file of applying a run-length encoding algorithm to this data file.

The file size will not be decreased/will increase because there are very few/no repeating patterns / because a run length of one would be added to each digit

What is the correct programming language translator for

this task:

A guessing game that can be used on

different computing platforms

Interpreter

What is the correct programming language translator for

this task:

A screen driver for a new

smartphone

Assembler

A new version of a spreadsheet

program for sale next year

Compiler

Control software for an embedded system inside a new washing machine

Assembler

Identify the measurement of network speeds.

A Mebibits per second

B Mebibytes per second

C Megabits per second

D Megabytes per second

The correct answer is C

A is not correct because mebibits is a measure of storage capacity

B is not correct because mebibytes is a measure of storage capacity

D is not correct because transmission speeds are measured only in bits per second, not bytes per second

Data packets contain the addresses of the sender and the receiver. Complete the table to give the number of bits that make up each type of network address.

Type Example Number of bits

IPv4 192.169.0.3

IPv6 1050:a500:00c0:0440:0006:0300:700d:436f

(1) IPv4 192.169.0.3 - 32 bits

(2) IPv6 1050:a500:00c0:0440:0006:0300:700d: 436f - 128 bits

Data packets travel over physical media.

Describe one difference between the media used by a wired network and a wireless network.

In a wired network packets travel over (copper/fibre-optic) cables/ electrical or light signals,

whereas in a wireless network packets travel over the air

Some people confuse Ethernet and Wi-Fi.

Describe what is meant by the term Ethernet.

Networking technology which uses a wired method to connect devices in a LAN such as computers, routers and printers

• Follow specific protocols to ensure data is sent and received correctly

• Used on a wired network/connection using Ethernet cables

• Defines how packets are checked for errors

• Defines speed of transmission

A single physical box connects a desktop computer to the Internet.

The box incorporates three different components.

Complete the diagram to show the names of the components in the correct order.

Desktop computer → ______ → _______→ ______→ Internet

Desktop computer → Switch → Router → Modem → Internet

Users enter passwords when logging onto a network and when creating accounts using a web page.

Describe one difference between validation and authentication.

VALIDATION: used to check that data/password entered by user is fit for processing/meets specified requirements

AUTHENTICATION: used to verify identity of user/prove that users are who they say they are

assembler

type of computer program that translates assembly language code into machine code so the computer's processor can directly execute it

interpreter

program that executes instructions written in a programming language directly, without requiring them to be pre-compiled into machine code

compiler

program that translates a programming language's source code into machine code which a computer can understand and execute

Computers are made up of hardware components.

Complete the diagram by adding directional arrows between the components to show the flow of communication.

Speaker CPU Mouse USB device

Mouse → CPU

CPU → Speaker

CPU ←→ USB Device

Identify what is stored in ROM.

A The software firewall

B The basic input output system

C The operating system

D The user interface code

The correct answer is B

A is not correct because a firewall is an application that is loaded after the device is booted

C is not correct because the operating system is loaded after the device is booted

D is not correct because the user interface is loaded after the device is booted

Cache is used as temporary storage.

One type of cache is located between main memory and the CPU.

Explain one reason cache is used in a computer.

• Cache makes up for the difference in speed of two devices because it is very high-speed memory

• Cache is high-speed memory which acts as a buffer between a faster and a slower device

• It speeds up processing because active/commonly used instructions and data are stored nearer to the CPU / the CPU doesn’t have to wait while instructions/data are fetched from RAM

A washing machine uses several different embedded systems.

One embedded system uses a switch to identify the type of wash cycle selected by the user.

Describe one other example of an embedded system found in a washing machine.

• Uses a sensor to check the water level in the machine

• Uses a thermometer to check the water temperature

• Uses a timer to control the time required for the wash cycle/rinse/drain/spin

• Uses a motor to rotate the drum