Computer Science 9618/12 May/June 2021: question paper and mark scheme
Cambridge AS & A Level Computer Science (9618), Paper 1 Theory Fundamentals, May/June 2021. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.
Raj owns houses that other people rent from him. He has a database that stores details about the people who rent houses, and the houses they rent. The database, HOUSE_RENTALS, has the following structure:
CUSTOMER(CustomerID, FirstName, LastName, DateOfBirth, Email)
HOUSE(HouseID, HouseNumber, Road, Town, Bedrooms, Bathrooms)
RENTAL(RentalID, CustomerID, HouseID, MonthlyCost, DepositPaid)
(a) Give the definition of the following database terms, using an example from the database
HOUSE_RENTALS for each definition.
Term Definition and example
Field
Entity
Foreign key
[6]
(b) Tick (3) one box to identify whether the database HOUSE_RENTALS is in Third Normal Form
(3NF) or not in 3NF.
Justify your choice using one or more examples from the database HOUSE_RENTALS.
In 3NF
Not in 3NF
Justification ……
…… [2]
(c) Example data from the table RENTAL are given:
RentalID CustomerID HouseID MonthlyCost DepositPaid
1 22 15B5L 1000.00 Yes
2 13 3F 687.00 No
3 1 12AB 550.00 Yes
4 3 37 444.50 Yes
(i) Complete the following Data Definition Language (DDL) statement to define the table
RENTAL.
CREATE …… …… (
RentalID INTEGER NOT NULL,
CustomerID INTEGER NOT NULL,
HouseID …… (5) NOT NULL,
MonthlyCost …… NOT NULL,
DepositPaid BOOLEAN NOT NULL,
…… (RentalID)
);
[4]
(ii) Write a Data Manipulation Language (DML) script to return the first name and last name of all customers who have not paid their deposit.
…… [4]
Mark scheme
1(a) 1 mark for definition, 1 mark for appropriate example in each 6
Term Definition and example
A column/attribute in a table
Field
e.g. CustomerID in the table CUSTOMER
Anything that data can be stored about
Entity
e.g. A customer or a house
Foreign A field in one table that is linked to a Primary Key in another
Key table e.g. CustomerID / HouseID in table RENTAL
1(b) 1 mark per bullet point to max 2 2
• All fields in all tables are dependant fully on the PK and on no other fields
• for example all fields in Customer table are fully dependent on
CustomerID
1(c)(i) 1 mark for each correctly completed line 4
CREATE TABLE RENTAL(
RentalID INTEGER NOT NULL,
CustomerID INTEGER NOT NULL,
HouseID VARCHAR (5) NOT NULL,
MonthlyCost REAL/CURRENCY NOT NULL,
DepositPaid BOOLEAN NOT NULL,
PRIMARY KEY (RentalID)
);
1(c)(ii) 1 mark per bullet point 4
• Select FirstName and LastName
• From both tables
• Where DepositPaid = No
• Joining tables (either AND, or INNER JOIN)
Example script:
SELECT FirstName, LastName
FROM CUSTOMER, RENTAL
WHERE DepositPaid = No
AND RENTAL.CustomerID = CUSTOMER.CustomerID;
Aisha manages a team of software developers.
(a) Explain the reasons why it is important that Aisha acts ethically in relation to her team members.
…… [2]
(b) The team are developing a computer game where the user plays a board game (such as chess) against the computer.
Describe how the computer would use Artificial Intelligence (AI) to play the board game.
…… [3]
(c) The final game will be released under a licence.
Tick (3) one or more boxes in each row to identify the licence(s) each statement describes.
Free Open
Commercial
Statement Software Source Shareware
Software
Foundation Initiative
The user can edit the source code
The user must always pay before being able to use the software
The user can redistribute the software
The user always gets a trial period
[4]
Mark scheme
2(a) 1 mark per bullet point to max 2 2
• To make sure the team members feel valued
• To get the best work out of the team
• To enable them to work well together
• To enable them to create the best product for the client
2(b) 1 mark per bullet point to max 3 3
• The rules / past moves / decision making algorithms of the game will be
stored
• The AI program is trained, by playing many times
• AI will look (ahead) at possible moves
• ... and/or analyse the pattern of past choices
• … and choose the move most likely to be successful
• Computer could learn how to improve // learn from previous mistakes
• … by storing the positive/negative result of choices
• ... and changing its future choices
2(c) 1 mark for each correct column 4
Free Open
Commercial
Statement Software Source Shareware
Software
Foundation Initiative
The user can edit
the source code
The user must
always pay before
being able to use
the software
The user can
redistribute the
software
The user always
gets a trial period
A logic expression is given:
S = (A AND B AND C) OR (B XOR C)
(a) Draw the logic circuit for the given expression.
A
B S
C
[4]
(b) Complete the truth table for the logic expression:
S = (A AND B AND C) OR (B XOR C)
A B C Working space S
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
[2]
Mark scheme
3(a) 1 mark for each correct gate, with correct inputs 4
3(b) 1 mark for each half (shaded) 2
A B C Working space S
0 0 0 0
0 0 1 1
0 1 0 1
0 1 1 0
1 0 0 0
1 0 1 1
1 1 0 1
1 1 1 1
The table shows part of the instruction set for a processor. The processor has one general purpose register, the Accumulator (ACC), and an Index Register (IX).
Instruction
Explanation
Opcode Operand
LDM #n Immediate addressing. Load the number n to ACC
Direct addressing. Load the contents of the location at the given address to
LDD <address>
ACC
STO <address> Store contents of ACC at the given address
ADD <address> Add the contents of the given address to the ACC
INC <register> Add 1 to the contents of the register (ACC or IX)
DEC <register> Subtract 1 from the contents of the register (ACC or IX)
CMP <address> Compare the contents of ACC with the contents of <address>
JPE <address> Following a compare instruction, jump to <address> if the compare was True
JPN <address> Following a compare instruction, jump to <address> if the compare was False
JMP <address> Jump to the given address
IN Key in a character and store its ASCII value in ACC
OUT Output to the screen the character whose ASCII value is stored in ACC
END Return control to the operating system
# denotes a denary number, e.g. #123
The current contents of the main memory and selected values from the ASCII character set are:
Address Instruction ASCII code table (selected codes only)
70 IN ASCII code Character
71 CMP 100 65 A
72 JPE 80 66 B
73 CMP 101 67 C
74 JPE 76 68 D
75 JMP 80
76 LDD 102
77 INC ACC
78 STO 102
79 JMP 70
80 LDD 102
81 DEC ACC
82 STO 102
83 JMP 70
100 68
101 65
102 100
(a) Complete the trace table for the program currently in main memory when the following characters are input:
A D
Do not trace the program any further when the third input is required.
Instruction Memory address
ACC address 100 101 102
68 65 100
[4]
(b) Some bit manipulation instructions are shown in the table:
Instruction
Explanation
Opcode Operand
AND #n Bitwise AND operation of the contents of ACC with the operand
AND <address> Bitwise AND operation of the contents of ACC with the contents of <address>
XOR #n Bitwise XOR operation of the contents of ACC with the operand
XOR <address> Bitwise XOR operation of the contents of ACC with the contents of <address>
OR #n Bitwise OR operation of the contents of ACC with the operand
OR <address> Bitwise OR operation of the contents of ACC with the contents of <address>
<address> can be an absolute address or a symbolic address
# denotes a denary number, e.g. #123
The contents of the memory address 300 are shown:
Bit Number 7 6 5 4 3 2 1 0
300 0 1 1 0 0 1 1 0
(i) The contents of memory address 300 represent an unsigned binary integer.
Write the denary value of the unsigned binary integer in memory address 300.
…… [1]
(ii) An assembly language program needs to test if bit number 2 in memory address 300 is a 1.
Complete the assembly language instruction to perform this test.
…… #4
[1]
(iii) An assembly language program needs to set bit numbers 4, 5, 6 and 7 to 0, but keep bits 0 to 3 with their existing values.
Write the assembly language instruction to perform this action.
…… [2]
Mark scheme
4(a) 1 mark for each shaded section / bullet point 4
• Load 65 into ACC
• Load 100 into ACC, increment and store in 102
• Load 68 into ACC
• Load 101 into ACC, decrement and store in 102
Memory address
Instruction
ACC
address
100 101 102
68 65 100
70 65
71
72
73
74
76 100
77 101
78 101
79
70 68
71
72
80 101
81 100
82 100
83
(70)
4(b)(i) 102 1
4(b)(ii) AND 1
4(b)(iii) 1 mark for AND, 1 mark for #15 2
AND #15
Seth uses a computer for work.
(a) Complete the following descriptions of internal components of a computer by writing the missing terms.
The …… transmits the signals to coordinate events based
on the electronic pulses of the …… .
The …… carries data to the components, while the
…… carries the address where data needs to be written to
or read from.
The …… performs mathematical operations and
logical comparisons.
[5]
(b) Describe the ways in which the following factors can affect the performance of his laptop computer.
Number of cores
Clock speed
[4]
(c) Seth accesses both software and data using cloud computing.
(i) Give two benefits of storing data using cloud computing.
1 ……
2 ……
[2]
(ii) Give two drawbacks of Seth using cloud computing.
1 ……
2 ……
[2]
(d) Draw one line from each term to its most appropriate description.
Term Description
It is only visible to devices within the Local
Area Network (LAN)
Public IP address
It increments by 1 each time the device connects to the internet
Private IP address A new one is reallocated each time a device connects to the internet
Dynamic IP address It can only be allocated to a router
It is visible to any device on the internet
Static IP address
It does not change each time a device connects to the internet
[4]
Mark scheme
5(a) 1 mark for each term correctly inserted 5
The control unit/bus transmits the signals to coordinate events based on the
pulses of the (system) clock.
The data bus carries data to components, while the address bus carries the
address where data is being written to or read from.
The arithmetic logic unit/ALU performs mathematical operations and logical
comparisons.
5(b) 1 mark per bullet point to max 3 per factor. max 4 overall. 4
Number of cores:
• Each core processes one instruction per clock pulse
• More/multiple cores mean that sequences of instructions can be split
between them
• … and so more than one instruction is executed per clock pulse // more
sequences of instructions can be run at the same time
• More cores decreases the time taken to complete task
Clock speed:
• Each instruction is executed on a clock pulse // one F-E cycle is run on
each clock pulse
• ... so the clock speed dictates the number of instructions that can be run
per second
• The faster the clock speed the more instructions can be run per second
5(c)(i) 1 mark per bullet point to max 2 2
• Cloud storage can be free (for small quantities )
• No need for separate (high capacity) storage devices // saves storage on
existing devices
• Can access data from any computer with internet access
• Most cloud data services will have in-built backup/disaster recovery
• Security could be better
• Can easily increase capacity
• Data can be easily shared
5(c)(ii) 1 mark per bullet point to max 2: 2
• Can only access (the cloud) with internet access
• Security may not be strong // no control over security
• There may not be any backups // no control over backups
• It can take a long time to upload/download the data
• It can be more expensive in the long term
• There could be a limit to the amount of storage unless paid for
• There could be compatibility/access issues
• There could be issues with the company offering cloud services
5(d) 1 mark for each correct line 4
A computer uses the ASCII character set.
(a) State the number of characters that can be represented by the ASCII character set and the extended ASCII character set.
ASCII ……
Extended ASCII ……
[2]
(b) Explain how a word such as ‘HOUSE’ is represented by the ASCII character set.
…… [2]
(c) Unicode is a different character set.
The Unicode value for the character ‘1’ is denary value 49.
(i) Write the hexadecimal value for the Unicode character ‘1’.
…… [1]
(ii) Write the denary value for the Unicode character ‘5’.
…… [1]
Mark scheme
6(a) 1 mark for each correct answer 2
ASCII = 128 // 27
Extended ASCII = 256 // 28
6(b) 1 mark per bullet point to max 2 2
• Each character has its own unique code
• Each character in the word is replaced by its code
• The codes are stored in the order in the word
6(c)(i) 31 1
6(c)(ii) 53 1
Jennifer is writing a computer program for her A Level homework.
(a) Jennifer uses a program library to help her write her computer program.
Describe how a program library can be used while writing a computer program.
…… [2]
(b) Jennifer uses an Integrated Development Environment (IDE) to write her computer program.
(i) The IDE allows Jennifer to use both an interpreter and a compiler while creating her computer program.
Describe the ways in which Jennifer can use both a compiler and an interpreter while developing the program.
…… [4]
(ii) Identify two debugging tools that a typical IDE can provide.
1 ……
2 ……
[2]
Mark scheme
7(a) 1 mark per bullet point to max 2 2
• Program libraries store pre-written functions and routines
• The program library can be referenced/imported
• the functions/routines can be called in her own program
7(b)(i) 1 mark per bullet point to max 4; max 3 from each section 4
Interpreter:
• Use an interpreter while writing the program
• … to test/debug the partially completed program
• … because errors can be corrected and processing continue from where
the execution stopped // errors can be corrected in real time // errors are
identified one at a time
Compiler:
• Use the compiler after the program is complete
• … to create an executable file
• Use the compiler to repeatedly test the same (completed) section
• … without having to re-interpret every time // compiler not needed at run-
time
7(b)(ii) 1 mark per correct tool to max 2 2
e.g.
• Breakpoints
• Single stepping
• Report windows
A company has several security measures in place to prevent unauthorised access to the data on its computers.
(a) Describe the difference between the security and privacy of data.
…… [2]
(b) Each employee has a username and password to allow them to log onto a computer. An employee’s access rights to the data on the computers is set to either read-only, or read and write.
Identify one other software-based measure that could be used to restrict the access to the data on the computers.
…… [1]
(c) The company is also concerned about threats posed by networks and the internet.
Identify two threats to the data that are posed by networks and the internet.
Threat 1 ……
Threat 2 ……
[2]
Mark scheme
8(a) 1 mark per bullet point 2
• Security protects data against loss
• Privacy protects data against unauthorised access
8(b) 1 mark for a correct answer 1
• Two factor authentication
• Biometric passwords
• Key Card Access
• Firewall
8(c) 1 mark per correct answer to max 2 2
• Malware // viruses // spyware // by example
• Hacking
• Phishing
• Pharming
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On this page, free: the mark scheme for AS & A Level Computer Science 9618/12, May/June 2021 (9618_s21_ms_12), and the question paper (9618_s21_qp_12), to read or download, with each question's marking points written out underneath.
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Computer Science 9618/12 for May/June 2021 is out of 75 marks, with 1 hour 30 minutes to answer it.
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