Computer Science Past paper

Explain the role of router in packet switching.

• A router examines the packets to find the destination IP address.
• It determines the fastest route for each packets
• It transmit the packets towards its destination
• It uses a routing table to keep track of the most efficient routes

Features of Magnetic storage

• It uses electromagnets.
• It has platters to store data.
• Platters are divided into tracks and sectors.
• It has a read/write head

Explain how the videos are compressed using lossless compresstion.

• A compression algorithm such as RLE is used.
• Repeating pixels/samples are identified and indexed with their repeated number
• And this uses temporal redundancy by recording the differences between each amplitude for sound

Explain why the error may not be detected by a parity byte check.

• Bits have been interchanged places.
• so total number of 1s in the byte is till odd
• so it will still meet the parity set

What is meant by ecryption key?

• A string of characters used to encrypt data
• and is used by an algorithm to encrypt or decrypt the data

Explain how access levels are used to help prevent a cyber security attack being successful.

• They restrict a user's access to data
• by giving users different permissions
• so an attacker will only have access to the data that the user has access to
• This prevents an attacker from installing malware
• and from viewing more confidential data.
• stops a malicious attacker from corrupting data

The app uses artificial intelligence (AI) to identify the name of the flower. Explain how the app can use AI to improve its ability to identify the correct name of the flower

• It can use machine learning by adapting its own rules.
• It can analyse patterns (in different flowers)
• It can use feedback from humans
• and store successful and unsuccessful identifications for improvement
• It can be trained by being shown pictures of flowers to learn in more detail

State what is meant by low-level language.

• It is a language that is closer to the language processed by a computer.

Describe the actions that take place in the decode stage of the FDE cycle.

• The instruction is sent to CIR which is in CU…
• …from MDR
• The CU decodes the instruction
• by using an instruction set.
• The instruction is decoded into Opcode and Operand.

Explain the purpose of the biometric device.

• For authentication
• to help keep the device secure
• to use as a login method for the device
• to allow the user to use a biological password

State what is meant by machine learning.

• A program that has the ability to automatically adapt its own data and processes

(d) The computer game has an expert system that can be used to find a solution to any problems with the game. The expert system uses an inference engine. Explain the role of the inference engine in finding a solution to a problem with the game.

• It takes data input by the user about the problem.
• It search for similar knowledge in the knowledge base.
• It applies it to the rule base to find the solution.
• It decide which question to ask next if needed.

Describe the role of the rule base in an expert system.

• Rule base stores the rules for the system.
• for the interference engine to use
• it is used to link the facts in the knowledge base

Describe what is meant by managing memory(2)

• keeping track of the status of each memory location.
• managing the movement of data to and from RAM
• checks that processes have enough memory located to them
• makes sure that two processes don't try to access the same memory location
• allows multitasking

Describe what is meant by a dynamic IP address.

• It can be used to uniquely identify a device on a network.
• It can change each time the device is connected to the network.

Reasons why the programmer would choose to write the computer program in a low‑level language instead of a high‑level language.

• can directly manipulate the hardware
• no requirement for the program to be portable
• Program will be more memory efficient
• quicker to execute
• can use specialised hardware

Digital currency

a currency that exists in electronic form only

Blockchain

a decentralised digital ledger or a database that stores all transactions made on the network.

What is a core?

• core is an individual processing unit inside a computer’s CPU that carries out FDE cycles. A core carries out one FDE cycle at a time. Using multiple cores can increase the performance of a computer.

What is a USB?

• A type of serial data transmission which has become the industry standard for connecting computers to devices via a USB port.

What is a software?

• a collection of instructions, data and programs written in programming language that tells a computer how to work and perform a specific task.
  / instructions that is used to operate a computer.

What is a system software?

• a type of computer program that manages computer hardware and provides a platform for running application software.

What is an application software?

• a computer program designed to help users perform specific task.

What is meant by cloud storage?

• A collection of servers that stores data in a remote location
• hardware can be owned by a third party
• data storage that is stored/accessed using the internet

State what is meant by a URL.

• a text-based address for a website/web page

Differences between hexadecimal and binary.

1. Binary is base-2 whereas hexadecimal is base-16
2. Binary onlh uses numbers whereas hexadecimal also uses letters// Binary only uses 0 and 1 whereas hexadecimal uses 0 to 9 and A to F

Similarity between hexadecimal and binary.

• they are both number systems

Describe the process of the logical left shift performed on the binary integer.

• Each bit in the binary number is shifted to the left.
• the left most significant bit is lost.
• A 0 is added as the right most significant bit.

State what effect this will have on the binary integer.

• the binary integer is multiplied by 2

Explain why the smartwatch needs ROM.

• To store the BIOS
• To store the bootstrap
• To help start-up the smart watch// to store start-up instructions
• To store the firmware
• For non-volatile storage//to store data permanently
• To store data/instructions that should not change unless needed

Explain how the odd parity check detects errors.

• The number of 1s are counted.
• A parity bit is added to each byte before transmission…
• …to make the sum of bits in each byte odd.
• After transmission, if the number if odd no error is detected.
• After transmission, if the number is even error is detected.

Explain how an ARQ operates using a positive acknowledgement method.

• Timer is started when sending device transmits a data packet to receiver.
• Receiving device checks the data packet for errors
• Once the receiving device knows the packet is error free it sends an acknowledgement before the timer ends
• … A time out occurs…
• the data packet is resent
• …until acknowledgement received or until max number of attempts reached

Describe the role of self-driving tractor and the farmer's computer in the echo check.(F/M/12/2024)

• The same data is transmitted back from computer to tractor.
• Tractor compares both sets of data…
• …if they are identical there is no error
• Tractor sends confirmation of accuracy if the same
• Tractor resends the data if they are different.

Describe the process of the checksum error detection method.

• The checksum is calculated from the data.
• ..using an algorithm
• The checksum value is transmitted with the data.
• The checksum value is recalculated after transmission by recipient
• If the checksum values do not match, an error is detected and request for data to be resent.
• If the checksum values match, no error is detected

Explain how ARQ using negative acknowledgement is used to establish that data is received without error.

• Receiver checks for errors
• ..by methods such as parity check or cyclic redundancy check
• If there is an error receiver transmits negative acknowledgement to sender
• If sender receives negative acknowledgement, it re-transmits the data
• If no negative acknowledgement is received before timeout, then successful receipt is assumed

Explain how the check-digit is used to check for errors in data entry.

• Check digit is calculated from the data.
• using an algorithm
• and input with the data
• computer recalculates the check digit using the same algorithm after input
• If the check digits match it has been input correctly
• If the check digit do not match it has been input incorrectly

Explain how the barcode scanning system operates to check for errors.

• A check digit is calculated from the barcode data…
• … using an algorithm…
• and added to the barcode.
• After the barcode is scanned , the check digit is recalculated…
• … using the same algorithm.
• If the check digits do not match an error has occurred when scanning the barcode//If the check digits match no error has occurred when scanning the barcode.