Computer Science 9618/12 May/June 2024: question paper and mark scheme
Cambridge AS & A Level Computer Science (9618), Paper 1 Theory Fundamentals, May/June 2024. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.
(a) Describe the operation of each of the following logic gates:
NAND ……
NOR ……
XOR ……
OR ……
[4]
(b) Draw a logic circuit for this logic expression:
X = NOT ((A AND B) OR (C AND D))
A
B
X
C
D
[2]
Mark scheme
1(a) 1 mark for each correct answer: 4
NAND
The output is 0 when both inputs are 1, otherwise the output is 1
NOR
The output is 1 when both inputs are 0, otherwise the output is 0
XOR
The output is 1 when one of the inputs is 1 and the other input is 0,
otherwise the output is 0
OR
The output is 0 when both inputs are 0, otherwise the output is 1
1(b) 1 mark for both AND gates with correct inputs 2
1 mark for correct OR and NOT gates with correct inputs and no superfluous
gates:
A computer game is being designed that users will be able to play using a virtual reality (VR) headset.
(a) Complete the description of the principal operation of a VR headset.
A headset can have one or two …… that output the image to
the user. The headset has speakers that output surround sound to give a realistic experience.
The user’s head movements are detected using a sensor.
This sensor is a …… . The data is transmitted to a
microprocessor that analyses the data to identify the …… of
movement. Some headsets use …… that record the user’s
eye movements for analysis.
[4]
(b) The computer uses a buffer when transmitting data to the VR headset.
Explain how a buffer is used when data is transmitted between the computer and the VR headset.
…… [3]
(c) The VR headset has Electrically Erasable Programmable Read Only Memory (EEPROM).
Explain the benefits of using EEPROM instead of other types of Read Only Memory (ROM) in the VR headset.
…… [3]
(d) The computer can transmit a video made from bitmap images and vector graphic animations to the VR headset.
(i) Describe how the data for a bitmapped image is encoded.
…… [3]
(ii) Describe the contents of a vector graphic drawing list.
…… [2]
(iii) The bitmap video is not compressed before transmission to the VR headset.
Give two reasons why the video does not need to be compressed.
1 ……
2 ……
[2]
Mark scheme
2(a) 1 mark for each correctly completed statement: 4
(LCD) displays/screens/lenses
gyroscope/accelerometer
direction/speed
digital cameras
A headset can have one or two (LCD) displays/screens/lenses that output
the image to the user. The headset has speakers that output surround sound
to give a realistic experience.
The user's head movements are detected using a sensor.
This sensor is a gyroscope/accelerometer. The data is transmitted to a
microprocessor that analyses the data to identify the direction/speed of
movement. Some headsets use digital cameras that record the user's eye
movements for analysis.
2(b) 1 mark each to max 3: 3
The buffer is used as a temporary store for data going to the headset
Data is transferred into the buffer by the computer
Data is retrieved from the buffer by the headset
When the buffer is empty/full an interrupt is sent to the computer
requesting more data/stopping further data being sent
When the headset has enough data/needs more data, an interrupt is sent
by the headset to the computer to stop sending data from buffer
2(c) 1 mark each to max 3: 3
EEPROM allows frequent/multiple read/write/erase operations
… so the headset can take advantage of new features
… without fully erasing the contents of the firmware in the headset first //
can erase a particular byte or the whole EEPROM
… without removing the chip(s)/firmware from the headset
... the contents of the firmware in the headset can be changed by the user
without technical expertise
Cheaper to manufacture so headset will be cheaper to purchase
2(d)(i) 1 mark each: 3
Image is made of pixels and each pixel has one colour
Each colour has a unique binary code
Code for the colour of each pixel is stored in sequence
2(d)(ii) 1 mark each to max 2: 2
List of objects in the drawing
A list that stores the command/description/equation required to draw each
object
Properties of each object e.g. the fill colour, line weight/colour
2(d)(iii) 1 mark each to max 2: 2
Dedicated connection to the headset // not sharing bandwidth
Already fast connection that can transmit the data without slowing
Video may already be a small file size and does not need further
reduction
Video is not saved so storage is not an issue in the headset
An assessment board scans exam papers and stores the digitised papers on a server. Exam markers download the digitised papers to mark. The exam markers then upload the mark for each paper.
(a) The assessment board needs to make sure the data stored on the server is secure.
(i) Authentication methods can help to protect the server against hackers.
Identify one other security measure that helps to protect the server from hackers.
Describe how the security measure works.
Security measure ……
Description ……
[3]
(ii) Identify one security measure that helps to protect the data when it is being transmitted to its destination. Describe how the security measure works.
Security measure ……
Description ……
[3]
(b) The exam markers use software that operates as a thin-client to mark the exam papers.
Complete the table by identifying two characteristics of a thin-client.
Describe how each characteristic will be used in this software.
Thin-client characteristic Description of use in this software
1
2
[4]
(c) Data transmitted on the internet passes through multiple different systems.
(i) Describe the role of routers in the transmission of data through the internet.
…… [2]
(ii) Describe the role of the PSTN (Public Switched Telephone Network) in the transmission of data through the internet.
…… [2]
Mark scheme
3(a)(i) 1 mark for security measure 3
1 mark each to max 2 for how the chosen measure works:
Firewall
Checks incoming connections
... against criteria
Blocks data from entering specific ports
Blocks data that does not meet whitelist that meets blacklist
Proxy server
Prevents devices accessing the web server directly
Intercepts any requests
Forwards the request using its own IP address
Screens returning data before sending it to the user
3(a)(ii) 1 mark for security measure 3
1 mark each to max 2 for description of the chosen measure:
Encryption
Encodes/scrambles data
... so if it is intercepted it cannot be understood
Algorithm/key is required to decode the data
3(b) 1 mark for characteristic 4
1 mark for description of application to examination software:
Thin-client characteristic Description of use in this software
Data is not stored on the Exam papers are stored on the server and
client computer not on the examiner’s computer // exam
papers are not permanently stored on the
examiners’ computers
Client computer is reliant on Examiners cannot mark if their device
access to server cannot access the server / the server ‘goes
down’
Client computer heavily The marking software will not operate
reliant on network/internet without network/internet access
connection
Client computer requires few Examiners can use devices with low
local resources/memory resources and the marking software will still
function
Client computer performs The marking software transmits requests,
minimal functions/processes the server responds and sends the
response to the user
3(c)(i) 1 mark each to max 2: 2
Receives packets from internet
Analyses the destination IP address of each packet
Forwards the packet towards its destination
... using the routing table
Maintains/updates the routing table
Finds the most efficient route to the destination
3(c)(ii) 1 mark each to max 2: 2
The PSTN consists of many different types of communication lines
… therefore the digital data may need to be converted into a different
form/analogue signal
Data is transmitted in both directions at the same time // duplex data
transmission
Using a PSTN the communication passes through different switching
centres/ISPs
An assessment board wants to store the marks students achieved in exams in a database named
RECORDS.
Part of the database design includes these two tables:
EXAM(ExamID, Subject, Level, TotalMarks)
EXAM_QUESTION(ExamQuestionID, ExamID, QuestionNumber, Question, MaxMark)
(a) Identify the relationship between EXAM and EXAM_QUESTION.
…… [1]
(b) Sample data for the table EXAM is shown:
ExamID Subject Level TotalMarks
00956124 Computer Science 2 75
00956125 Computer Science 3 120
00956126 Mathematics 2 100
00956127 Mathematics 3 150
00956128 Physics 2 70
00956129 Physics 3 80
Write a Structured Query Language (SQL) script to define the table EXAM.
…… [3]
(c) The table EXAM_QUESTION has been created but the foreign key has not been linked.
Write an SQL script to update EXAM_QUESTION and link the foreign key to EXAM.
…… [2]
(d) The database also needs to store data about the students, the exams the students have taken and the marks the students achieved in each question of each exam.
Describe the additional tables that will need to be included in the database and explain how all the tables in the database will be linked.
…… [5]
Mark scheme
4(a) 1 mark for: 1
1-to-many
4(b) 1 mark each: 3
Creating table EXAM with opening and closing brackets
All fields with appropriate data types and commas at end of lines
ExamID as primary key
Example:
CREATE TABLE EXAM(
ExamID varchar NOT NULL,
Subject varchar,
Level int,
TotalMarks int,
PRIMARY KEY(ExamID)
);
4(c) 1 mark each: 2
Altering table EXAM_QUESTION
Linking ExamID to ExamID in EXAM
Example.
ALTER TABLE EXAM_QUESTION
ADD FOREIGN KEY (ExamID) REFERENCES EXAM(ExamID);
4(d) 1 mark each to max 5: 5
STUDENT table identified with suitable Primary Key
A linking table between STUDENT and EXAM with suitable Primary Key
and appropriate name
… that includes the Primary Key of the STUDENT table as a Foreign Key
to join with STUDENT
... and includes the Primary Key of the EXAM table as a Foreign Key to
join with EXAM
A linking table between STUDENT and EXAM_QUESTION with suitable
Primary Key and appropriate name
… that includes the Primary Key of Table 2 as a Foreign Key to join with
Table 2
… that stores the ExamQuestionID and the mark for that question
The following table shows part of the instruction set for a processor. The processor has two registers: 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
LDD <address> address to ACC
Indirect addressing. The address to be used is at the given address.
LDI <address>
Load the contents of this second address to ACC
Indexed addressing. Form the address from <address> + the contents
LDX <address> of the index register. Copy the contents of this calculated address to
ACC
LDR #n Immediate addressing. Load the number n to IX
ADD #n/Bn/&n Add the number n to the ACC
ADD <address> Add the contents of the given address to the ACC
SUB #n/Bn/&n Subtract the number n from the ACC
SUB <address> Subtract the contents of the given address from the ACC
INC <register> Add 1 to the contents of the register (ACC or IX)
<address> can be an absolute or a symbolic address
# denotes a denary number, e.g. #123
B denotes a binary number, e.g. B01001010
& denotes a hexadecimal number, e.g. &4A
(a) The current contents of memory are shown:
Address Data
10 1
11 3
12 5
13 11
14 10
15 16
16 12
The current contents of the ACC and IX are shown:
ACC 10
IX 0
Complete the table by writing the content of the ACC after each program has run.
Program number Code ACC content
LDI 15
1
SUB #1
LDD 14
2
ADD 11
LDM #11
3 ADD #3
SUB 16
LDR #2
4 LDX 14
ADD #2
[4]
(b) The processor includes these bit manipulation instructions:
Instruction
Explanation
Opcode Operand
AND #n/Bn/&n Bitwise AND operation of the contents of ACC with the operand
Bitwise AND operation of the contents of ACC with the contents of
AND <address>
<address>
XOR #n/Bn/&n Bitwise XOR operation of the contents of ACC with the operand
Bitwise XOR operation of the contents of ACC with the contents of
XOR <address>
<address>
OR #n/Bn/&n Bitwise OR operation of the contents of ACC with the operand
Bitwise OR operation of the contents of ACC with the contents of
OR <address>
<address>
<address> can be an absolute or a symbolic address
# denotes a denary number, e.g. #123
B denotes a binary number, e.g. B01001010
& denotes a hexadecimal number, e.g. &4A
The current contents of memory are shown:
Address Data
25 11000110
26 11100001
27 10000001
28 11001101
29 00001111
The current content of the ACC is shown:
0 1 0 0 0 1 1 0
Complete the table by writing the content of the ACC after each program has run.
The binary number 01000110 is reloaded into the ACC before each program is run.
Program number Code ACC content
1 XOR 29
2 AND #29
3 OR B11111111
[3]
Mark scheme
5(a) 1 mark for each correct answer: 4
Program Code ACC Content
Number
1 LDI 15 11
SUB #1
2 LDD 14 13
ADD 11
3 LDM #11 2
ADD #3
SUB 16
4 LDR #2 14
LDX 14
ADD #2
5(b) 1 mark for each correct answer: 3
Program Code ACC Content
Number
1 XOR 29 0100 1001
2 AND #29 0000 0100
3 OR B11111111 1111 1111
A computer has an Operating System (OS).
Memory management and process management are two OS tasks.
Explain how memory management and process management support multi-tasking.
…… [4]
Mark scheme
6 1 mark each to max 4 4
Max 3 marks for each management task:
Memory management: Max 3 marks
Stores data from all currently running programs concurrently in RAM
Stops the data from overwriting each other in RAM/primary storage
Decides which processes should be in main memory
Makes efficient use of memory
Process management: Max 3 marks
Allows one process to be paused whilst another process can be actioned
Decides which process is to be run next
Switches between processes to allow them to share the use of the
processor
Identification/description of scheduling
A computer stores binary data.
(a) Tick (3) one box only to identify the largest file size.
3300 kibibytes
0.3 megabytes
3 mebibytes
3300 kilobytes
[1]
(b) Subtract the denary number 10 from the denary number 100 using binary subtraction.
Show your working.
Working ……
Answer ……
[3]
(c) Convert the hexadecimal number C0F into denary.
Show your working.
Working ……
Answer ……
[2]
Mark scheme
7(a) 1 mark for: 1
3300 kibibytes
7(b) 1 mark each: 3
Converting 100 to binary 0110 0100 and 10 to binary 0000 1010
Subtraction method - converting 10 to – 10 and adding // direct
subtraction …
… correct answer 0101 1010
Method 1: Converting to -10 and adding:
Binary for +10 is 0000 1010
Binary for –10 is 1111 0110
Binary for 100 is 0110 0100
100 + (-10):
01100100
+1 1 1 1 0 1 1 0
(1) 0 1 0 1 1 0 1 0
Carries: 1 1 0 0 1 0 0 0
Method 2: Direct Subtraction
Borrows:
00011010
01100100
–00001010
01011010
7(c) 1 mark for working: 2
1100 0000 1111 // 2048 + 1024 + 8 + 4 + 2 + 1
// (12 * 162) + 15 // (12 * 16 * 16) + 15 // 3072 + 15
1 mark for correct answer:
3087
A programmer uses an Integrated Development Environment (IDE) to write a computer program.
The IDE has both a compiler and an interpreter as built-in translators.
(a) The programmer decides to use the compiler when testing the final program.
Describe the benefits of using the compiler during testing.
…… [2]
(b) IDEs have many features other than built-in translators.
Complete the table by identifying one other common IDE feature that can be used for each purpose. Describe how each feature helps the user during program development.
Each feature must be different. Do not give translator as one of your features.
Purpose IDE feature Description
for coding ……
for presentation ……
for debugging ……
[6]
(c) The programmer uses program libraries when developing the program.
Describe two benefits to the programmer of using program libraries.
1 ……
2 ……
[2]
Mark scheme
8(a) 1 mark each to max 2: 2
Creates an executable file
… so the code can be tested multiple times without having to recompile
… so repeated testing takes less time
8(b) 1 mark for identification of each feature and 1 mark for matching description: 6
e.g.
For coding:
IDE feature Description
Context-sensitive Gives suggestions for code as the user
prompts types instead of having to write/remember
the code
Auto-correct Corrects spelling mistakes so that user has
fewer errors to correct
For presentation:
IDE feature Description
Pretty-printing Colour code keywords so the user can
identify any errors
Expand/collapse (code) The user can hide code that they are not
blocks currently working on
For debugging:
IDE feature Description
Single stepping Run the code one line at a time // shows
the effect of each line of code
Breakpoints Stop the code running at a set point to
check the flow/variable contents
8(c) 1 mark each to max 2: 2
Saves programming/testing time as code does not have to be written/re-
written from scratch // code does not have to be tested
Code is already tested so it is more robust/likely to work
The programmer does not need to maintain the library // library routines
are updated automatically
Can perform complex calculations that the programmer may be unable to
do
Makes code more easily readable
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Where can I find the 9618/12 May/June 2024 mark scheme?+
On this page, free: the mark scheme for AS & A Level Computer Science 9618/12, May/June 2024 (9618_s24_ms_12), and the question paper (9618_s24_qp_12), to read or download, with each question's marking points written out underneath.
How many marks is 9618/12 out of?+
Computer Science 9618/12 for May/June 2024 is out of 75 marks, with 1 hour 30 minutes to answer it.
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