9618/11 Paper 1 October/November 2024

State one difference between a tebibyte and a gigabyte.

A tebibyte = 2^40 bytes (binary), whereas a gigabyte = 10^9 bytes (decimal).

State one reason why binary addition and subtraction can result in overflow.

The result is too large or too small to be represented in the given number of bits.

Give one limitation of a file-based approach and explain how a relational database addresses it.

Limitation: Data redundancy.

Explanation: Relational databases use linked tables to reduce duplication by storing data only once.

Define these terms: Referential integrity, Candidate key, Tuple.

• Referential Integrity: Ensures all foreign keys match a valid primary key.

• Candidate Key: A field that could uniquely identify a record (not necessarily chosen as the primary key).

• Tuple: A single row or record in a table.

State the purpose of the system clock and Control Unit (CU).

• System Clock: Synchronises CPU operations by sending timing signals.

• Control Unit (CU): Directs operations of the processor; manages instruction execution and data flow.

Identify another processor feature (besides number of cores) that affects performance and explain.

• Feature: Clock speed.

• Reason: Higher speed = more instructions processed per second.

Identify a port for connecting a solid state drive and explain how automatic recognition works.

• Port: USB.

• Explanation: When connected, the voltage change is detected. The OS checks the device ID, finds the corresponding driver, and automatically loads it to enable use.

Two disadvantages of using DRAM over SRAM.

• DRAM requires constant refreshing to maintain data, while SRAM does not.

• DRAM has slower access speed compared to SRAM, reducing performance.

Describe how an optical disc reader/writer works.

The process begins when the disc is spun at high speed by the drive mechanism.
At the same time, a laser beam is shone onto the surface of the disc through an optical head.
The laser follows a spiral track starting from the centre and moving outward.
When writing, the laser burns small pits into the surface of the disc to represent digital data.
When reading, the laser detects differences in reflection between pits (burned areas) and lands (untouched areas), allowing the data to be interpreted.

Explain the use of a buffer when writing data to an optical disc.

• The computer and disc writer operate at different speeds.

• A buffer allows temporary storage of data.

• The computer sends data to the buffer at a higher speed.

• The writer reads data from the buffer at its slower speed

Describe file management tasks carried out by an OS.

• Maintains/creates directory structures.

• Specifies logical file storage methods (e.g., FAT, NTFS).

• Provides file naming conventions.

• Controls user access and software access to files.

Explain the need for back-up software.

• To allow data to be retrieved/restored when lost.

• To automatically make regular duplicate copies of data.

• So the user doesn't have to remember to back up manually.

Explain the benefits of the attachment being a compressed file.

• Uses less of the storage space (more work can be stored).

• Transmission time is reduced (quicker download).

• Bandwidth usage is reduced (less impact on other transmissions).

• Less data is used on the email system.

Describe one lossless method of compressing a text file.

Run-Length Encoding (RLE): Replaces repeated sequences of the same character with a single character and a count of occurrences.

Explain the benefits to the student of using library files when writing a program.

• Saves development time by using pre-written code.

• Less testing is needed as routines are already tested.

• Enables inclusion of complex features the student may not be able to write.

• Results in a more robust and error-free program.

Identify and describe one other presentation feature in an IDE besides prettyprint.

• Feature: Auto-indentation.

• Description: Automatically formats code as the user types, making structure clearer and improving readability.

Identify and describe one other debugging feature in an IDE besides single stepping.

• Feature: Breakpoints.

• Description: Pauses execution on a specific line so the user can inspect variable values or program state at that moment.

Complete the table to identify the most appropriate type of sensor for each scenario.

• A door is open:

• Daylight level is below a set amount:

• Person detected within 2 metres:

• A door is open: Pressure sensor / Infra-red sensor

• Daylight level is below a set amount: Light sensor

• Person detected within 2 metres: Infra-red sensor

Explain what is NOT in a monitoring system

• There is no use of feedback

• The output does not affect the input data from sensors.

• The system does not include actuators.

Explain how artificial intelligence is used in the car park system to identify the car’s registration number.

• It uses image recognition.

• The pixels of each image from the camera are stored.

• They are matched to the expected shape/size/colour of a registration number.

• It uses Optical Character Recognition (OCR).

• The pixels within the identified area are analysed and compared to expected characters/letters/numbers.

Give two benefits of distributing software using a shareware licence.

• The user can trial the software before purchasing to check if it meets their needs.

• There is no initial cost, making it accessible.

Give two benefits of distributing software using a commercial licence.

• The developer can earn a fee from each sale.

• Comprehensive support is usually offered to help resolve problems.

Describe the purpose of the Status Register (SR).

• Stores the value of flags/bits set or cleared by arithmetic or logical operations.

• These flags can be checked to influence the next instruction or decision in the program.

Identify two differences between general-purpose and special-purpose registers.

Special-purpose registers have a fixed role in the machine (e.g., PC, SR), while general-purpose registers can be used freely by the programmer.

Special-purpose registers hold execution state (e.g., current instruction address or status), while general-purpose registers temporarily hold data during operations.