A Level Computer Science 9618 Paper 13, Oct/Nov 2024

Output is only 1 if one input is 1 and the other is 0 // Output is only 1 if both inputs are different // Output is only 0 if both inputs are the same

((A NOR B) AND (A OR B))

NAND (B AND C)

NOT gate, 2 correct AND gates and the NAND gate

OR gate and the final AND gate

DRAM requires constant refreshing, but SRAM does not need to be constantly refreshed

DRAM generally has greater capacities per chip, but SRAM generally has lower capacities per chip

The computer and the hard disk drive transmit and receive at different speeds // The computer transfers data faster than the HDD can receive

The buffer is used for temporary storage

… so that the computer can transfer data to the buffer at the higher speed

... and is not held up waiting for data to transfer

The system uses feedback

The system acts independently

Input data causes the car to brake

Foreign key: BatchID, table BATCH

Foreign key: CustomerID, table CUSTOMER

SELECT SUM(Quantity)

FROM SALE WHERE and one correct condition

AND with remainder correct conditions

Create table BATCH with opening and closing brackets, all statements within brackets

BatchID, Type and Flavour as varchar or equivalent

…with suitable constraint(s)

Size as decimal, SellingPrice as currency, EndDate as date (or equivalent)

Primary key identified as BatchID

Ice cream table with an appropriate name

… containing type, flavour, size, selling price

… with suitable primary key

… foreign key identified in BATCH that links to the primary key in ICECREAM

Entity: A real-life object that is represented as a table

Attribute: An item of data about an entity

Referential integrity is enforced

… such as cascade update/delete // if the data is changed in one place it is updated in every other place

... and ensures each foreign key has a corresponding primary key

A fee is charged for the software. The source code cannot be accessed. Users do not get a free trial.: Commercial

Users can try the software before buying it. Users may not be able to access all features during the trial.: Shareware

Software is usually free of charge. Users can access the source code and alter the program to their needs.: Open Source // Free software

The professional ethical body has ethical guidelines to follow

Clients/staff know the computer programmer is reputable

The professional ethical body provides help and support

ASCII // UNICODE (identification)

7/8 bits per character // represents 128/256 characters // represents all characters from Latin alphabet // 8/16/32 bits per character // represents 256/65536+ characters // represents all characters in all languages (matching description)

256 // 2^8

Increased file size

The change may not be noticeable // Data removed is usually not noticed by the human eye

It produces a larger decrease in file size compared to lossless // Lossy decreases file size considerably

Value/magnitude/size of the analogue sound wave is measured a set number of times each second/time / at set intervals

Each sample/reading/measurement is given the binary number and stored in sequence

Decrease sample rate // Decrease sample resolution // Sound outside of set/human hearing range is removed

Matching expansion: fewer samples/readings/measurements stored per second // fewer bits per second stored // fewer bits per sample/reading/measurement // each sample has fewer bits // fewer measurements are stored / decreases the number of possible binary values so fewer bits are stored

158 (for instruction sequence 1: LDD 50, ADD #4, ADD 54)

99 (for instruction sequence 2: LDI 53, DEC ACC, ADD 56)

50 (for instruction sequence 3: LDM #55, SUB #5)

A bit manipulation operation is required to set all the bits to zero

Compare the result of the masking with 0 // the result of comparison will be true if the register is cleared

AND B00000000 / #00 / &00

Denary value: 8107

Flip each bit then add 1 … // Most significant 1 bit is treated as the corresponding negative denary value …

… method of converting the new binary number into denary // … add the other positive corresponding denary values

Denary value: −97

A logical shift moves all bits to the right and inserts zeros in the appropriate leftmost bits

An arithmetic shift moves all bits to the right but copies the sign bit into the Most Significant Bit (MSB)

A WAN covers a large geographical area

External/public infrastructure is used

Fibre optic

Transmits data as pulses of light

Radio waves / microwaves

Transmits electromagnetic waves on different frequencies

Data is compressed before transmitting

The video and audio are transmitted continuously as a series of bits

The video is uploaded to a media server

On download, the media server sends the data to a buffer // The buffer stores data from server until the receiving device can process it // The receiving device receives the bit stream from the buffer

Public IP address: So that the router is visible to the Internet/external network/WAN

Private IP address: So that the router is identified to computers within the LAN

It allows the network to be divided into smaller networks

… which reduces traffic in some parts of the network // reduces congestion // because traffic only travels through the parts necessary // which hides the complexity of network // and allows for easier maintenance of the network