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AQA A LEVEL COMPUTER SCIENCE PAPER 2 JUNE 2023 QUESTION PAPER (7517-2) - Copy.pdf
Typology: Exams
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Forename(s)
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I declare this is my own work.
Materials
For this paper you must have:
Instructions
the box around each page or on blank pages.
this book. Write the question number against your answer(s).
be marked.
Information
Advice
shading a lozenge alongside the appropriate answer as shown.
shown.
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
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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]
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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.
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. 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:
[2 marks]
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12
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. 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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. 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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. 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.
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[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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12
. Explain why the volatile environment (the contents of registers) must be saved before
an interrupt is serviced.
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[2 marks]
. Explain the relationship between hardware and software.
[1 mark]
Turn over for the next question
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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 number of bedrooms and the number of bathrooms that a property has.
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.
property.
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]
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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
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Representation 1 Representation 2
{"Properties":[
{ "PropertyID": 8026,
"HouseNum": "12",
"Street": "Chester Drive",
"Bedrooms": 4 },
{ "PropertyID": 9034,
"HouseNum": "23a",
"Street": "Castle Street",
"Bedrooms": 5 }
Shade one lozenge to identify the method of encoding used by Representation 2.
[1 mark]
. 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.
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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:
The list of properties returned should only include, for each property, the following
details:
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]
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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]
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. 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.
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[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:
packet directly to Computer B across the LAN or if the packet must be sent via the
Internet
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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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]
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Question 6 continues on the next page
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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:
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.
Figure 7 to help you to work out the final output Q
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[4 marks]
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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10
. Using the rules of Boolean algebra, simplify the following Boolean expression.
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You must show your working.
[4 marks]
Answer
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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.
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[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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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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