12 marksmedium
The colour of each pixel in a bitmapped image is represented by 8 bits.
A bitmap image can be compressed using lossy compression.
Explain the reasons why lossy compression is often suitable for a bitmap image.
Computer Science — AS
Practice Paper 2 (Cambridge International AS Computer Science)
Exam code:961816 questions · 80 marks · ≈ 1 hour · spans 16 of 29 topics
Assembled from the topic question banks — not an official Cambridge International paper26 marksmedium
2 marks
(b)
A computer system stores text, images and sound.
The colour of each pixel in a bitmapped image is represented by 8 bits.
(i) State the largest number of different colours that can be represented by 8 bits.
(1 mark)
(ii) State one drawback of increasing the number of bits that represents each pixel in the bitmap image.
(1 mark)
4 marks
(c)
(i) Explain how an analogue sound wave is converted into digital data.
(2 marks)
(ii) Describe one method of compressing a sound file using lossy compression.
(2 marks)
38 marksmedium
5 marks
(a)
A business is creating a local area network (LAN) in its office.
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 marks)
3 marks
(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 mark)
(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.
(2 marks)
47 marksmedium
3 marks
(a)
Describe the principal operations of a 3D printer.
2 marks
(b)
Describe the purpose of a temperature sensor within the 3D printer.
2 marks
(c)
A 3D printer contains 1GB of Dynamic RAM (DRAM) to store print data.
State two advantages of the printer having Dynamic RAM instead of Static RAM (SRAM).
54 marksmedium
2 marks
(a)
Complete the truth table for the logic expression:
X = (A XOR B) NAND (A AND (B XOR C))
| A | B | C | Workspace | X |
|---|---|---|---|---|
| 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 marks
(b)
Draw the logic circuit for the logic expression:
W = P NAND ((Q OR NOT R) XOR (P XOR Q))
63 marksmedium
(a)
The following table shows part of the instruction set for a processor. The processor has two registers, the Accumulator (ACC) and the Index Register (IX).
| Instruction | Explanation | |
|---|---|---|
| Opcode | Operand | |
LDM | #n | Immediate addressing. Load the number n to ACC |
LDD | <address> | Direct addressing. Load the contents of the location at the given address to ACC |
LDI | <address> | Indirect addressing. The address to be used is at the given address. Load the contents of this second address to ACC |
LDX | <address> | 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 | <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) |
DEC | <register> | Subtract 1 from the contents of the register (ACC or IX) |
| 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 |
|---|---|
| 50 | 54 |
| 51 | 55 |
| 52 | 50 |
| 53 | 52 |
| 54 | 100 |
| 55 | 25 |
| 56 | 50 |
The current contents of the ACC and IX are shown:
| ACC | 50 |
|---|---|
| IX | 45 |
Complete the table by writing the content of the ACC after each program has run.
| Instructions | ACC content | |
|---|---|---|
| 1 | LDD 50 ADD #4 ADD 54 | |
| 2 | LDI 53 DEC ACC ADD 56 | |
| 3 | LDM #55 SUB #5 |
72 marksmedium
(c)
Describe the difference between a right logical binary shift and a right arithmetic binary shift.
83 marksmedium
(d)
Identify one port that could be used to connect the virtual reality headset to the laptop.
Justify your choice.
99 marksmedium
4 marks
(a)
A programmer uses both a compiler and an interpreter to translate a program written in a high-level language.
Describe the advantages of using the interpreter compared to the compiler to translate the program.
1 mark
(b)
State one reason why some high-level languages are partially compiled and partially interpreted.
4 marks
(c)
(i) Identify two features that support the visual presentation of the code in a typical Integrated Development Environment (IDE).
(2 marks)
(ii) Identify two features that support the debugging of the code in a typical IDE.
(2 marks)
101 markmedium
(c)
The program makes use of complex statistical functions. The required functions are not built-in to the programming language and are too complicated for the programmer to write.
One solution would be to employ another programmer who has experience of writing these functions, as there is no time to train the existing programmer.
State one other way that these functions may be provided for inclusion in the program.
114 marksmedium
(c)
An example of a tutor ID is NK16C6.
An administrative officer enters the tutor ID into the TUTOR table.
Explain how data verification can be used when the tutor ID is entered.
126 marksmedium
1 mark
(a)
State the meaning of privacy of data.
1 mark
(b)
State the meaning of integrity of data.
4 marks
(c)
Describe the following threats to a computer system.
Phishing email
Spyware
134 marksmedium
A bank allows customers to access their accounts using an application that they can download onto a device such as a smartphone.
The bank also needs to keep its customers’ data private and secure.
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.
148 marksmedium
The table shows sample data for the table REPAIR_PART.
| PartID | RepairNumber | Quantity |
|---|---|---|
| ACD128SA | 0022 | 3 |
| PPOR543DWW | 0022 | 1 |
| TR453 | 0023 | 1 |
| PPOR543DWW | 0023 | 2 |
| WED5 | 0024 | 5 |
Write a Structured Query Language (SQL) script to define the table REPAIR_PART.
Include constraints (restrictions) on the data that can be entered into each field where appropriate.
(5 marks)
(iii) Suppliers send invoices to the company for the parts that are used. A new table, INVOICE, stores the data about each invoice and whether it has been paid or not.
The design for the table INVOICE is shown:
INVOICE(InvoiceID, SupplierID, AmountDue, Paid, DatePaid)
The table shows sample data for the table INVOICE.
| InvoiceID | SupplierID | AmountDue | Paid | DatePaid |
|---|---|---|---|---|
| 000001 | JK675 | 22.50 | TRUE | 01/01/2024 |
| 000002 | WR443 | 358.99 | FALSE | |
| 000003 | JK675 | 10.21 | FALSE |
Write an SQL script to return the total amount due to the supplier with the ID of JK675 for all the invoices that have not currently been paid.
159 marksmedium
3 marks
(a)
A shop repairs electronic devices, for example mobile phones and tablet computers. The shop owner stores the data about the repairs using a file-based approach.
Give one limitation of using a file-based approach to store the data and explain how a relational database addresses this limitation.
Limitation.......................................................................................................
Explanation.....................................................................................................
3 marks
(b)(i)
The shop owner creates a relational database called FIXIT.
The database stores data about the customers and the devices for repair.
Some devices need new parts that are ordered from suppliers.
The database FIXIT is designed to include the following tables:
PART(PartID, Description, Price, SupplierID)
CUSTOMER(CustomerID, FirstName, LastName, ContactNumber)
REPAIR(RepairNumber, StartDate, EndDate, CustomerID, Device)
REPAIR_PART(PartID, RepairNumber, Quantity)
Complete the entity-relationship (E-R) diagram for the given tables.
3 marks
(c)
Complete the table by writing a definition for each of the database terms.
| Term | Definition |
|---|---|
| Referential integrity | ..................................................... |
| Candidate key | ...................................................... |
| Tuple | ........................................................ |
164 marksmedium
(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 .......................................................................................................