Learn Extracted exam questions A-Level Computer Science 9618 Computer Science June 2024 Question paper 11
9618 Computer Science June 2024 Question paper 11
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1 (a) Tick (✓) one box to identify the correct logic statement for this truth table. A B C X 0 0 0 1 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 0 1 0 1 0 1 1 0 1 1 1 1 0
NOT (A AND B AND C)
(A XOR B) NOR C
(A OR B OR C) NOR C
NOT A AND NOT B AND NOT C
[1]
(b) Draw a logic circuit for the logic expression: X = NOT (NOT A AND (NOT B XOR C)) A X B C
[2]
2 A video doorbell is attached to the front door of a house. The doorbell uses a motion sensor to detect when a visitor walks in front of the door. When the motion sensor is activated: • The digital camera in the doorbell starts recording a video. • A message is transmitted to a smartphone so that the person who lives in the house can watch the video. The doorbell also has a button that can be pressed. When the button is pressed, a message is transmitted to a smartphone to play the doorbell sound. The videos are stored on the doorbell’s internal secondary storage device and overwritten when the secondary storage device is full.
(a) The video doorbell can be considered an example of an embedded system.
Identify two characteristics of the doorbell that suggest it is an embedded system. 1 2 [2]
(b) State whether the video doorbell is a monitoring system or a control system.
Justify your choice. Monitoring or control system Justification [2]
(c) The video doorbell has both primary memory and secondary storage.
(i) Identify two items of data that the video doorbell will store in primary memory. 1 2 [2]
(ii) The video doorbell has a solid state (flash) secondary storage device.
Complete the table by writing the answer or answers to each statement about the principal operation of solid state (flash) memory. Statement Answer the two types of logic gate that can be used to create solid state devices 1 2 the number of transistors contained in each cell the type of gate that can retain electrons without power the type of gate that allows or stops current from passing through [4]
(iii) The video doorbell uses a buffer.
Describe how the video doorbell will use the buffer [2]
(d) The digital camera has a microphone which is used to record the sound for the video.
The user changes the sampling rate that the microphone uses from 44.1 kHz to 88.2 kHz.
Describe how this change in sampling rate will affect the performance of the video doorbell [3]
(e) The video doorbell allows both real-time and on-demand bit streaming.
(i) State what is meant by bit streaming [1]
(ii) Give two differences between real-time and on-demand bit streaming. 1 2 [2]
3 A software developer is writing a computer program.
(a) The developer uses an interpreter while writing the program code because it is easier for debugging.
Explain one reason why it is easier to debug the program code using an interpreter instead of a compiler [2]
(b) The program is ready to be sold to customers.
The developer uses a compiler because it creates an executable file.
Explain the reasons why the need to create an executable file makes the complier the appropriate choice when the program is complete [3]
4 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 LDD
Direct addressing. Load the contents of the location at the given address to ACC LDI Indirect addressing. The address to be used is at the given address. Load the contents of this second address to ACC LDX Indexed addressing. Form the address from + the contents 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 Add the contents of the given address to the ACC SUB #n/Bn/&n Subtract the number n from the ACC SUB Subtract the contents of the given address from the ACC INC(a) The current contents of memory are shown: Address Data 19 24 20 2 21 1 22 3 23 5 24 4 25 22
The current contents of the ACC and IX are shown: ACC 12 IX 1
Complete the table by writing the content of the ACC after each program has run. Program number Code ACC content 1 LDD 20 ADD #2 2 LDX 22 3 LDI 25 INC ACC SUB 22 4 LDD 19 LDM #5 LDM #25
[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 AND
Bitwise AND operation of the contents of ACC with the contents of XOR #n/Bn/&n Bitwise XOR operation of the contents of ACC with the operand XOR Bitwise XOR operation of the contents of ACC with the contents of OR #n/Bn/&n Bitwise OR operation of the contents of ACC with the operand OR Bitwise OR operation of the contents of ACC with the contents of 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. &4AThe current contents of memory are shown: Address Data 30 01110101 31 11111111 32 00000000 33 11001100 34 10101010
The current content of the ACC is shown: 1 0 0 1 1 0 1 0
Complete the table by writing the content of the ACC after each program has run.
The binary number 10011010 is reloaded into the ACC before each program is run. Program number Code ACC content 1 AND 31 2 XOR B01001111 3 OR #30
[3]
5 A bank allows customers to access their accounts using an application that they can download onto a device such as a smartphone.
(a) The system that allows customers to access their accounts using the application is a client-server model.
Describe the roles of the different devices in this model [4]
(b) The bank wants to protect the integrity of its data while transferring the data to other banks. Parity check is one example of data verification.
Complete the description of parity check when Computer A is transmitting data to Computer B.
Computer A and Computer B agree on whether to use parity. Computer A divides the data into groups of The number of 1s in each group is counted. If the agreed parity is and the group has an even number of 1s, a parity bit of 1 is appended, otherwise a parity bit of 0 is appended.
In a parity check the bytes are grouped together, for example in a grid. The number of 1s in each column (bit position) is counted. A bit is assigned to each column to make the column match the parity. These parity bits are transmitted with the data as a parity [5]
(c) The bank also needs to keep its customers’ data private and secure.
(i) The bank’s network has a firewall.
Explain how a firewall can help protect the customers’ data [3]
(ii) Customers need to use biometric authentication to access their accounts.
One biometric authentication method is facial recognition.
Facial recognition uses Artificial Intelligence (AI).
Describe how AI is used in facial recognition [4]
6 A company is developing a website that will allow users to create an account and then play a quiz every day. The data about the users and the quizzes are stored in a database.
A user must select a unique username and enter a valid email address to create an account. All users must be over the age of 16. A new quiz is given to the users every day. Each quiz is stored in its own text file.
The database stores the filename of each quiz and the date it can be played. The user gets a score for each quiz they complete, which is stored in the database. The scores are used to give each user a rating, for example Gold.
(a) Create a 3-table design for this database normalised to Third Normal Form (3NF).
Give your table design in the format:
TableName(PrimaryKey, Field1, Field2, …) [6]
(b) The company is using a Database Management System (DBMS) to set up the database.
Describe what is meant by the following DBMS features: Data dictionary Logical schema [4]
(c) The company has another database, FARMING, for a different game.
The database FARMING has a table named EVENT which is shown with some sample data. PlayerID EventID Category Points 000123 3 Build 100 000124 1 Grow 36 000123 4 Grow 22 000123 7 Create 158 000125 3 Grow 85 000125 4 Build 69
(i) The database FARMING has a second table created named PLAYER that has the primary key PlayerID.
The field PlayerID in EVENT needs to be set up as a foreign key to link to PlayerID in PLAYER.
Write a Structured Query Language (SQL) script to change the table definition for EVENT to link the foreign key to PLAYER [2]
(ii) Write an SQL script to return the number of events that each player has completed [3]
7 Complete the binary addition. Show your working.
1 0 0 1 1 1 1 0 0 1 1 0 0 0 0 1
- 0 0 0 1 1 0 0 1
[3]
8 A business is creating a local area network (LAN) in its office.
(a) The business is deciding which topology to use.
Tick (✓) one or more boxes in each row to identify the topology, or topologies, each statement describes. Statement Bus Star Mesh all devices connect to one central device all devices connect to a central cable multiple paths for the packets to travel along robust against damage because if any line fails, the rest of the network retains full functionality most likely to lose data through collisions
[5]
(b) The LAN will connect to the internet through a router. The router has a public IPv6 address.
(i) State why the router has a public IP address [1]
(ii) One difference between an IPv4 and IPv6 address is that the numbers in an IPv4 address are separated by full stops and in an IPv6 address they are separated by colons.
Identify two other differences between an IPv4 and IPv6 address. 1 2 [2]