A Level Computer Science 9618 Paper 31, Oct/Nov 2024

correct answer // statement regarding number losing precision/rounding error

number converted to binary 201.125 = 11001001.001 // 128 + 64 + 8 + 1 + 0.125 / 1/8 seen

use of the exponent e.g. moving the binary point 8 places / × 2^8.

application of exponent to go from 1.010110011 to 101011.0011 // x 2^5 // movement of binary point 5 places seen

–32 + 8 + 2 + 1 + .125 + .0625 // –32 + 8 + 2 + 1 + 1/8 + 1/16 seen // –1 + ¼ + 1/16 + 1/32 + 1/256 + 1/512 // –1 + 179/512 // –333/512

–20.8125 // –20 13/16

low number of instruction formats //low number of instruction sets

uses single-clock cycle instructions

uses fixed length instructions

uses many general-purpose registers

A dedicated circuit / channel is required

The circuit is established before the transmission begins

The circuit lasts for the whole of the transmission // The circuit is closed at the end of the transmission

Benefit: MP1 No need for data to be reassembled // data / frames arrive in the same order in which they were sent // MP2 Suitable for real time transmission // fast data transfer rate // MP3 The whole of the bandwidth is available

Drawback: MP4 No other transmission can use the same circuit when it is in use // Bandwidth can be wasted as it cannot be used by other messages // MP5 Not secure // Can be intercepted as all data travelling along the same route // MP6 If there is a problem with the route the transmission ends // No other route is available without first doing the setup // MP7 The circuit is always there whether or not it’s being used // MP8 Can take time to set up before transmission starts.

Each layer can only accept input from the next higher layer or the next lower layer

There is an interface between the adjacent layers which is the only interaction between layers

Data is added to the headers as the frames/packets pass through the layers

The interactions are carried out by installed software

A hashing algorithm is used in direct access methods on random and sequential files

It is a mathematical formula

… used to perform a calculation applied to the key field of the record being searched / stored

The record is stored in the next free memory space after the one identified by the hashing algorithm // Use linear progression

An overflow area is set up and the record is stored in the next free memory space in the overflow area.

A set user-defined data type is a composite data type

… which includes a list of unordered elements

Set theory operations, such as intersection and union, can be applied to these elements

TYPE SymbolSet/Operators =

SET OF CHAR

DEFINE Operators/SymbolSet

('+', '–', '*', '/', '^') // : SymbolSet/Operators

First two correct products

Next two correct products

Final two correct products

Two marks if no errors present, One mark if one error present

Correct loop for group of 4 (columns 11, 10; rows 01, 11)

Correct loop for wraparound group of 4 (columns 00, 10; rows 01, 11)

Any correct Boolean term

Boolean terms and operator correct and no other terms present

(T =) D. (A + B̅)

In segmented memory, the logical / virtual address space is broken into varying sized blocks called segments / sections.

Each segment has a name and size.

During execution segments from logical / virtual memory are loaded into physical memory.

The address is specified by the user // … it contains the segment name and offset value.

Disk thrashing is a problem that may occur when virtual memory is being used.

As the main memory fills up, more and more pages need to be swapped in and out of virtual memory.

This swapping leads to a very high rate of hard disk access / excessive disk head movements.

To ensure that the attributes are only accessible using the class's own methods/within the class.

Two correct attributes with sensible names and correct data types.

Constructor present.

Two correct setters with exact names and appropriate parameters and data types.

Two correct getters with appropriate names.

Name assigned to pet name getter matches the attribute.

<operator> ::= + | – | * | /

<label> ::= <letter><digit>|<letter><digit><digit>

<equation> ::= <label> =

<label><operator><label>

begin with either a letter or a symbol

end with either one or two symbols

digit and all other connections and label correct.

<password> ::= <letter><digit><symbol>|

<letter><digit><symbol><symbol>|<symbol><digit><symbol>|<symbol><digit><symbol><symbol>

Four additional nodes with correct data values

Correct null pointers in all added nodes (6) with no extra null pointers where the arrow points to the next node

Correct arrows to represent pointers joining parent nodes to child nodes

All nodes in correct order and no extra data added to pointers.

Correct Red and Green rows

Correct Yellow and Blue rows

Correct Orange, Indigo and Violet rows

Correct FreePtr with blank row 7

NowPtr  RootPtr and WHILE NowPtr <> -1

IF BinTree[NowPtr].Data > Item THEN NowPtr  BinTree[NowPtr].LeftPtr

ELSE IF BinTree[NowPtr].Data < Item THEN NowPtr  BinTree[NowPtr].RightPtr

ELSE RETURN NowPtr and RETURN NowPtr after ENDWHILE