A Level Computer Science 9618 Paper 31, Oct/Nov 2023

conversion of 65.25 to binary seen e.g. 1000001.01 = 65.25 // 64 + 1 + 0.25 / ¼

correct mantissa: 0 1 0 0 0 0 0 1 0 1 0 0

correct exponent: 0 1 1 1

the decimal fraction 0.20 cannot be represented exactly (the closest is 0.25 / 0.1875)

therefore, there will be a loss of precision due to a rounding error/truncation

HTTP connected to: when transmitting hypertext documents

BitTorrent connected to: to provide peer-to-peer file sharing

SMTP connected to: when sending email messages towards the intended destination

IMAP connected to: when retrieving email messages from a mail server over a TCP/IP connection

To ensure correct network protocols are followed

To enable the upper layers to access the physical medium // enables connection/ communication with the internet / network layer

A user-defined non-composite (data type) (only award once) [enumerated type]

…with a list of all possible values

A user-defined non-composite (data type) (only award once) [pointer type] / …that stores addresses/memory locations only

…and indicates the type of data stored in the memory location.

Records (in the file) are ordered

…based on the key field

Records are stored in no particular order within the file // There is no sequencing in the placement of the records

There is a relationship between the key of the record and its location within the file // a hashing algorithm is used to find the location of the record

Start at the beginning of the file

…check records linearly // …until the desired record is found // … processing / updating records as required //… EOF found.

Single Instruction, Single Data (architecture). // Data is taken from a single source and a single instruction is performed on the data.

Contains one processor, a control unit and a memory unit // …that executes instructions sequentially.

Multiple Instruction, Multiple Data (architecture). // At any time, any processor can execute different instructions on different sets of data.

Contains many processors // …that operate asynchronously / independently.

First shaded block (rows 1 to 4) correct for column Z: 1, 0, 1, 0

Second block (rows 5 to 8) and third block (rows 9 to 12) correct for column Z: 1, 0, 1, 0 and 1, 0, 1, 0

Fourth shaded block (rows 13 to 16) correct for column Z: 1, 0, 0, 0

Working point 1: (Y =) Ā.B̄.C̄.D̄ + Ā.B̄.C.D̄ + Ā.B.C̄.D̄ + Ā.B.C.D̄

Working point 2: Factorising terms e.g. (Y =) Ā.D̄.(B̄.C̄ + B̄.C + B.C̄ + B.C)

(Y =) Ā.D̄

Benefit: The user interface hides the complexities of the computer hardware/operating system from the user // It provides appropriate access systems for users with differing needs // Complex commands involving memory locations/buses/computer hardware/ are avoided

Valid example: Clicking on icon rather than writing code // Using a graphical user interface / icons for navigation

Blocked (state)

When the time slice of the running process expires (round robin).

…and there is a process with a higher priority in the ready queue, the running process is pre-empted // When an interrupt arrives at the CPU, (the process running on the CPU gets pre-empted).

AccountFile  "AccountRecords.dat"

OPENFILE AccountFile FOR RANDOM

Location  Hash(Customer.AccountNumber)

SEEK AccountFile, Location

GETRECORD AccountFile, Customer

(Exception handling is the process of) responding to an unexpected event when the program is running so it does not halt unexpectedly

Programming errors / User errors

Hardware failure / Runtime errors

(5 – 2)

* (5 + 4) / 9

Ring 1 correct (push 5, push 2, subtract to get 3)

Ring 2 correct (push 5, push 4, add to get 9)

Ring 3 correct (multiply 3 and 9 to get 27)

Ring 4 correct (push 9, divide 27 by 9 to get 3)

Evaluate the RPN expression from left to right

Push each element of the RPN expression onto the stack in order until an operator is reached

Pop the last two elements from the stack and apply the operator // Push the result of the operation onto the stack // Repeat the process until the whole expression is evaluated.

Correct constant declaration

Two correct variable declarations

Correct array declaration

FUNCTION Pop() RETURNS REAL

IF TopPointer >= BasePointer THEN

Item  Stack[TopPointer]

TopPointer  TopPointer – 1

RETURN Item

A queue is a first in first out / FIFO data structure and a stack is a first in last out / FILO / LIFO data structure // Data is removed from a queue in the order it is received and removed from a stack in the reverse order to which it is received

Both ADTs can vary in size / are of indeterminate length // Data is popped and pushed (onto/from a stack) at the same end but it is enqueued and dequeued (to/from a queue) at different/opposite ends // a queue has two accessible ends and a stack has only one // A stack has only one moveable pointer whereas a queue has two.

(22) student(anthony).

(23) choice1(anthony, history).

(24) choice2(anthony, geography).

X = tomaz, pietre, nico

student(N)

subject(S)

choice1(N, S)

all logical operators correct with no additional code (see example answers)

An artificial neural network is the component of artificial intelligence that is meant to simulate the functioning of a biological brain.

Artificial neural networks are a key component of machine learning.

They can solve problems that would prove impossible or difficult for humans // Artificial neural networks have self-learning capabilities that enable them to produce better results as more data becomes available

Artificial neural networks can be layered (input, hidden and output layers) // Artificial neural networks have many interconnected layers, some / many of which are hidden // Weights are assigned between nodes // Weights are adjusted through training to give a more accurate result // More complex learning capabilities / more accurate results are available with larger numbers of hidden layers