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AQA A LEVEL COMPUTER SCIENCE PAPER 2 JUNE 2023 QUESTION PAPER (7517-2) - Copy.pdf, Exams of Nursing

AQA A LEVEL COMPUTER SCIENCE PAPER 2 JUNE 2023 QUESTION PAPER (7517-2) - Copy.pdf

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Download AQA A LEVEL COMPUTER SCIENCE PAPER 2 JUNE 2023 QUESTION PAPER (7517-2) - Copy.pdf and more Exams Nursing in PDF only on Docsity!

Please write clearly in block capitals.

Centre number Candidate number

Surname

Forename(s)

Candidate signature

I declare this is my own work.

A-level

COMPUTER SCIENCE

Paper 2

Monday 1 9 June 2023 Morning Time allowed: 2 hours 30 minutes

Materials

For this paper you must have:

  • a calculator.

Instructions

  • Use black ink or black ball-point pen.
  • Fill in the boxes at the top of this page.
  • Answer all questions.
  • You must answer the questions in the spaces provided. Do not write outside

the box around each page or on blank pages.

  • If you need extra space for your answer(s), use the lined pages at the end of

this book. Write the question number against your answer(s).

  • Do all rough work in this book. Cross through any work you do not want to

be marked.

Information

  • The marks for questions are shown in brackets.
  • The maximum mark for this paper is 100.

Advice

  • In some questions you are required to indicate your answer by completely

shading a lozenge alongside the appropriate answer as shown.

  • If you want to change your answer you must cross out your original answer as

shown.

  • If you wish to return to an answer previously crossed out, ring the answer

you now wish to select as shown.

For Examiner’s Use

Question Mark

1 2 3 4 5 6 7 8 9

10

11

TOTAL

Do not write

outside the

4

Answer all questions.

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A sound has been sampled and recorded. The sound was sampled for 1 minute and

40 seconds at a sample rate of 8000 Hz with a 16 - bit sample resolution.

A sample rate of 1 Hz means that one sample has been taken every second.

Calculate the minimum amount of storage space, in bytes , needed to store the

sampled sound.

You should show your working.

[2 marks]

Answer

. 2 An analogue to digital converter (ADC) was used during the sampling process.

Explain the principles of operation of an ADC.

[2 marks]

Do not write

outside the

Turn over ►

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Questions 02.2 , 02.3 , 02.4 and 02.5 use a normalised floating point representation

with a 7 - bit mantissa and a 5 - bit exponent, both stored using two’s complement.

Non-integer values such as - 1.65 and 23/1068 can be represented by a computer

using a fixed point or a floating point system.

State one advantage of using a floating point system over a fixed point system and

one advantage of using a fixed point system over a floating point system.

You should assume that the two systems use the same number of bits to store a

value.

[2 marks]

Advantage of floating point

Advantage of fixed point

The following is a floating point representation of a number:

Calculate the decimal equivalent of the number.

Express your answer to at least four decimal places or as a fraction. You should

show your working.

[2 marks]

Answer

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Questions 02.2 , 02.3 , 02.4 and 02.5 use a normalised floating point representation

with a 7 - bit mantissa and a 5 - bit exponent, both stored using two’s complement.

box

. Write the normalised floating point representation of the decimal value 1632 in the

boxes below.

You should show your working.

[3 marks]

Answer

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Questions 02.2 , 02.3 , 02.4 and 02.5 use a normalised floating point representation

with a 7 - bit mantissa and a 5 - bit exponent, both stored using two’s complement.

. State, in decimal , the highest (most positive) and lowest (most negative) values that

could be represented by this floating point system.

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You should show your working.

[3 marks]

Highest value Lowest value

. When the decimal value 28.25 is converted into binary using this floating point

system, a rounding error occurs.

Explain:

  • why a rounding error has occurred, and
  • what the system might do when the value 28.25 is converted into binary.

[2 marks]

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12

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outside the

. Figure 1 shows how some of the components inside a computer are connected

together. The computer uses the von Neumann architecture. Some of the names of

components have been omitted from Figure 1 and replaced with the numbers  to

Figure 1

Complete Table 1 by writing in the Component Number column the numbers from

Figure 1 that correspond to the Component Names.

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[2 marks]

Table 1

Component Name Component Number (1–5)

Address Bus

Data Bus

Main Memory

Processor

USB I/O Controller

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outside the

. The computer has 4 gibibytes of memory installed. How many kibibytes is this

equivalent to?

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[1 mark]

Answer

. A tablet computer uses the Harvard architecture. Describe two advantages of using

the Harvard architecture compared to the von Neumann architecture.

[2 marks]

Advantage 1

Advantage 2

Question 3 continues on the next page

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outside the

. The diagram in Figure 2 describes the fetch part of the Fetch-Execute cycle. Some of

the names of registers have been omitted from the figure and replaced with the

numbers  to 

Figure 2

State the full names of the registers that should appear in the diagram where the

numbers are.

box

[2 marks]

Number Full Name of Register

. Interrupts can be generated by devices connected to the processor during the

Fetch-Execute cycle.

Describe the role of interrupts.

[2 marks]

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outside the

12

. Explain why the volatile environment (the contents of registers) must be saved before

an interrupt is serviced.

box

[2 marks]

. Explain the relationship between hardware and software.

[1 mark]

Turn over for the next question

Turn over ►

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outside the

An estate agency makes details of the properties that it has for sale available to

potential customers through a website. The details of the properties and other data

that are useful to the agency are stored in a relational database.

The individual web pages about specific properties that a customer can view are

generated dynamically by a program from the data in the database.

A client-server system, which uses CRUD and REST, is used to provide details of

properties in a web page that is being viewed in a web browser on a client computer.

Figure 3 shows the structure of the relations in the database.

Figure 3

Property(PropertyID, HouseNum, Street, Area, Postcode, Bedrooms,

Bathrooms, AskingPrice, SellerID)

Seller(SellerID, Title, Forename, Surname, Telephone)

Buyer(BuyerID, Title, Forename, Surname, Telephone, DesiredArea,

MinBedrooms, MaxPrice)

Viewing(BuyerID, PropertyID, ViewingDate, ViewingTime)

Sale(SaleID, PropertyID, BuyerID, SalePrice)

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  • The Property relation stores details of the properties that are for sale. This includes

the number of bedrooms and the number of bathrooms that a property has.

  • The Seller relation stores details of people who are selling the properties.
  • The Buyer relation stores details of the people who are looking to buy a property

and information about the type of property they want, including the area that they

want to live in, the minimum number of bedrooms that they need in a property and

the maximum price that they are prepared to pay.

  • An entry is made in the Viewing relation whenever a buyer arranges to look at a

property.

  • An entry is made in the Sale relation whenever a property is sold to a buyer. The

SalePrice may be different to the AskingPrice for the property.

. The list below contains four statements about the principles of CRUD and REST.

One of these statements is false.

Shade one lozenge to indicate which statement is false.

A CRUD is an acronym for Create, Retrieve, Update, Delete.

B REST allows JavaScript to communicate with the server using the HTTP

protocol.

C The database is connected to the web browser using REST.

D The REST API will be created and run on the client computer.

[1 mark]

Do not write

outside the

An SQL query is executed to retrieve some details about properties with at least four

bedrooms in a particular area. The following two records are found:

PropertyID HouseNum Street Bedrooms

8026 12 Chester Drive 4

9034 23a Castle Street 5

These records could be sent from the server to the client using XML or JSON.

Figure 4 shows the query results encoded using each of these methods.

Figure 4

box

Representation 1 Representation 2

{"Properties":[

{ "PropertyID": 8026,

"HouseNum": "12",

"Street": "Chester Drive",

"Bedrooms": 4 },

{ "PropertyID": 9034,

"HouseNum": "23a",

"Street": "Castle Street",

"Bedrooms": 5 }

]}

8026

12

Chester Drive

4

9034

23a

Castle Street

5

Shade one lozenge to identify the method of encoding used by Representation 2.

[1 mark]

A JSON

B XML

. State two reasons why it could be argued that JSON is better than XML.

[2 marks]

Reason 1

Reason 2

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. A composite primary key has been selected for the Viewing relation. This consists of

the attributes BuyerID, PropertyID and ViewingDate.

box

In selecting these attributes to form the primary key, what assumption has the

database designer made about the behaviour of the buyers?

[1 mark]

Figure 3 is repeated below so that you can answer Question 04.5 without having to

turn back in the question paper.

Figure 3

Property(PropertyID, HouseNum, Street, Area, Postcode, Bedrooms,

Bathrooms, AskingPrice, SellerID)

Seller(SellerID, Title, Forename, Surname, Telephone)

Buyer(BuyerID, Title, Forename, Surname, Telephone, DesiredArea,

MinBedrooms, MaxPrice)

Viewing(BuyerID, PropertyID, ViewingDate, ViewingTime)

Sale(SaleID, PropertyID, BuyerID, SalePrice)

. Write an SQL query that will retrieve from the database the list of all properties that

the buyer with BuyerID 23 might be interested in buying. The properties should:

  • be in the buyer’s desired area
  • have at least the minimum number of bedrooms the buyer requires
  • cost no more than the maximum price that the buyer is prepared to pay.

The list of properties returned should only include, for each property, the following

details:

  • the PropertyID
  • the street that the property is on
  • the number of bedrooms that the property has
  • the asking price for the property.

The list should be ordered with the most expensive property at the top of the list and

the least expensive at the bottom of the list.

[5 marks]

Do not write

outside the

box

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10

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outside the

Figure 5 shows a computer ( Computer A ) which is located on a LAN in the UK. It is

connected, via the Internet, to an email server ( Computer B ) which is located on a

LAN in Belgium.

Computer A has IP address 192.168.2.3 and Computer B has the public IP address

Figure 5

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. The computers on subnet 192.168.2.0 have been configured using the DHCP system.

State one advantage of using the DHCP system.

[1 mark]

Do not write

outside the

. Computer A has the IP address 192.168.2.

Many other computers connected to the Internet have the same IP address.

Explain how two or more computers connected to the Internet can have the same IP

address and still communicate with each other.

box

[2 marks]

. In addition to routing, Router A3 also acts as a firewall to protect the computers on

the LAN in the UK.

Explain four different ways that a firewall can protect computers on a LAN.

[4 marks]

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. A packet of data is to be transmitted across the Internet from Computer A in the UK

to Computer B in Belgium. A checksum will be used to attempt to detect if any errors

have occurred during the transmission.

Explain how:

  • Computer A will use a subnet mask to determine whether or not it can send the

packet directly to Computer B across the LAN or if the packet must be sent via the

Internet

  • the packet will be routed across the Internet
  • the checksum can be used to determine if the received packet has been changed

during the transmission.

In your answer you will be assessed on your ability to follow a line of reasoning to

produce a coherent, relevant and structured response.

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[12 marks]

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outside the

19

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Table A

Inputs Output

Table B

Inputs Output

Table C

Inputs Output

Table D

Inputs Output

. Figure 6 shows truth tables for four logic gates. The truth tables are labelled Table A ,

Table B , Table C and Table D.

Figure 6

Shade in one lozenge to indicate which truth table does not represent one of the

logic gates: OR, XOR, NOR.

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Table A

Table B

Table C

Table D

[1 mark]

Do not write

outside the

Question 6 continues on the next page

DO NOT WRITE ON THIS PAGE

ANSWER IN THE SPACES PROVIDED

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outside the

A 7-segment display is a component used to display a digit on devices such as

calculators. A 7-segment display consists of seven lights (called segments) which can

be illuminated individually to make the shapes of digits. For example, the digit 3 could

be displayed by illuminating five of the seven segments like this (black shading

indicates an illuminated segment):

Figure 7 shows part of a logic circuit which is designed to take a binary representation

of a single decimal digit as its input and light up the segments to display the decimal

digit. The part of the circuit shown controls the lighting of just one segment of the

display.

Figure 7

The inputs to the circuit are X3 , X2 , X1 and X0. Together these form the binary

representation of the decimal digit to display. For example, if the inputs to the circuit

were:

X3 X2 X1 X

then the display would need to show this pattern:

as 0101 is the binary representation of the decimal digit 5

The output Q is connected to one segment of the display. When Q is 1 this segment

lights up, when it is 0 the segment does not light up.

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. Complete every empty cell in the truth table below for the circuit in Figure 7 - The listed inputs to the table ( X3 , X2 , X1 , X0 ) represent the decimal digits 0 – 9 in

binary, which are the only allowed inputs.

  • The letters AE have been used to label intermediate points on the circuit in

Figure 7 to help you to work out the final output Q

  • Some of the cells have been completed for you.

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[4 marks]

INPUTS INTERMEDIATE POINTS OUTPUT

X3 X2 X1 X0 A B C D E Q

Figure 8 shows the patterns of segments that are illuminated for each of the decimal

digits 0 – 9.

Figure 8

. By considering the inputs and outputs of the circuit in Figure 7 and consulting your

trace table, state which of the segments in the display (labelled a to g below) the

output Q from the circuit is controlling.

[1 mark]

Output Q is controlling segment

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outside the

10

. Using the rules of Boolean algebra, simplify the following Boolean expression.

A

A

B

∙ A

B

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You must show your working.

[4 marks]

Answer

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outside the

One of the numbers listed below is a member of the set of integers, the set of rational

numbers and the set of real numbers, but is not a member of either the set of

irrational numbers or the set of natural numbers.

Shade one lozenge to indicate which number this is.

box

A – 43

B

C

D 107.834

[1 mark]

2 Shade one lozenge to indicate which type of number would be most appropriate to

use to measure the length of an item, such as a piece of rope.

[1 mark]

A Integer

B Irrational

C Natural

D Rational

E Real

Turn over for the next question

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2

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outside the

A warehouse stores products that are waiting to be delivered to supermarkets. The

products are packed onto pallets. For example, a pallet might hold 120 boxes of

washing powder. All of the products on one pallet are of the same type.

The individual products on the pallets could be identified by labelling them individually

with barcodes or by attaching RFID (radio-frequency identification) tags to them.

Each barcode/RFID tag would store a representation of a ProductID number that

uniquely identifies the type of product (eg 102546 might represent a specific brand

and box size of washing powder) together with an ItemID number that is unique to the

specific item (eg box number 1 of the washing powder, box number 2 of the washing

powder etc).

Figure 9 shows an example of five boxes of washing powder loaded onto a pallet and

their ProductID and ItemID values.

Figure 9

Figure 10 shows an excerpt from the simple database table that stores the details of

the products that the warehouse has in stock.

Figure 10

ProductID Description QuantityInStock

102546 Washing Powder 1kg box 10 000

398352 Baked Beans 455g tin 1450

293820 Large Dishcloths 300

Some pallets delivered to the warehouse will be of products that already exist in the

database table. Other deliveries will be of pallets of items that don’t exist in the table

because the warehouse has not stocked them before.

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. Explain why the warehouse owners might prefer the individual products to be

identified using RFID tags.

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[2 marks]

. Explain why the product manufacturers or supermarket owners might prefer the

individual products to be identified using barcode labels.

[2 marks]

Question 8 continues on the next page

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