Oxford Cambridge and RSA Examinations
GCE
Computer Science
H446/01: Computer systems
Advanced GCE
Mark Scheme for Autumn 2021Oxford Cambridge and RSA Examinations
OCR (Oxford Cambridge and RSA) is a leading UK awar
...
Oxford Cambridge and RSA Examinations
GCE
Computer Science
H446/01: Computer systems
Advanced GCE
Mark Scheme for Autumn 2021Oxford Cambridge and RSA Examinations
OCR (Oxford Cambridge and RSA) is a leading UK awarding body, providing a wide range of
qualifications to meet the needs of candidates of all ages and abilities. OCR qualifications
include AS/A Levels, Diplomas, GCSEs, Cambridge Nationals, Cambridge Technicals,
Functional Skills, Key Skills, Entry Level qualifications, NVQs and vocational qualifications in
areas such as IT, business, languages, teaching/training, administration and secretarial skills.
It is also responsible for developing new specifications to meet national requirements and the
needs of students and teachers. OCR is a not-for-profit organisation; any surplus made is
invested back into the establishment to help towards the development of qualifications and
support, which keep pace with the changing needs of today’s society.
This mark scheme is published as an aid to teachers and students, to indicate the requirements
of the examination. It shows the basis on which marks were awarded by examiners. It does not
indicate the details of the discussions which took place at an examiners’ meeting before marking
commenced.
All examiners are instructed that alternative correct answers and unexpected approaches in
candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills
demonstrated.
Mark schemes should be read in conjunction with the published question papers and the report
on the examination.
© OCR 2021H446/01 Mark Scheme
Annotation Meaning
Omission mark
Benefit of the doubt
Subordinate clause / consequential error
Incorrect point
Expansion of a point
Follow through
Not answered question
No benefit of doubt given
Point being made
Repeat
Correct point
Too vague
Zero (big)
Blank Page – this annotation must be used on all blank pages
within an answer booklet (structured or unstructured) and on
each page of an additional object where there is no candidate
response.
Level 1
Level 2
1. AnnotationsH446/01 Mark Scheme
Level 3
• Subject Specific Marking Instructions
Question Answer Mark Guidance
1 (a) i • Clock speed
• Number of cores
• Cache
2
AO1.1
Accept
Use of pipelining/size of pipeline
Use of out of order execution
Use of SIMD instructions
Integrated graphics processing on CPU
ii • RAM is volatile
• Used for storing programs/data/parts of OS
currently in use
• ROM is non volatile
••
Used for storing (e.g.) BIOS / bootstrap
4
AO1.2
iii • Performing complex numerical calculations
• Calculations on matrices / vectors / multiple data at
the same time
• …e.g. insurance pricing, modelling risk, calculating
bills
2
AO2.2
Example has to relate to insurance company
(b) • Concurrent processing of multiple instructions
• One instruction can be fetched while previous is
being decoded…
• And the one before is being executed.
• In case of a branch pipeline is flushed.
• Increases speed of execution
3
AO1.1
(c) Mark Band 3–High Level (7-9 marks) 9 AO1
Magnetic devices include magnetic hard drives and
magnetic tape.H446/01 Mark Scheme
The candidate demonstrates a thorough knowledge and
understanding of magnetic and solid state storage. The
material is generally accurate and detailed.
The candidate is able to apply their knowledge and
understanding directly and consistently to the context
provided. Evidence/examples will be explicitly relevant
to the explanation.
The candidate provides a thorough discussion which is
well balanced. Evaluative comments are consistently
relevant and well-considered.
There is a well-developed line of reasoning which is
clear and logically structured. The information
presented is relevant and substantiated.
Mark Band 2-Mid Level (4-6 marks)
The candidate demonstrates reasonable knowledge
and understanding of magnetic and solid state storage;
the material is generally accurate but at times
underdeveloped.
The candidate is able to apply their knowledge and
understanding directly to the context provided although
one or two opportunities are missed.
Evidence/examples are for the most part implicitly
relevant to the explanation.
The candidate provides a sound discussion, the
majority of which is focused. Evaluative comments are
for the most part appropriate, although one or two
opportunities for development are missed.
There is a line of reasoning presented with some
structure. The information presented is in the most part
relevant and supported by some evidence.
Mark Band 1-Low Level (1-3 marks)
AO1.1 (2),
AO1.2 (2),
AO2.1 (2),
AO3.3.
(3)
Data stored by altering the magnetic field of a small
section of the tape or disk; one orientation represents a
binary value of 1, the opposite orientation represents a
binary value of 0. Written to using a read head.
Read head can then read the magnetic field and
retrieve the data.
These read and write heads move across the disk or
the tape moves under the heads.
Solid state devices store data using semiconductors;
drives can be based on NAND Flash or DRAM. No
moving parts are required.
Backup involves copying potentially large amounts of
data to and from storage devices at regular intervals.
Servers distribute data to client devices.
AO2
Magnetic hard drives entirely suitable for storing
operating system, software and data. Large capacity,
cheap (by comparison) purchasing price and reliability
make them idea for heavy use in an insurance office.
Solid state drives have no moving parts and offer an
increase in speed and quicker access to customer
records. However, smaller capacity (in comparison)
may be an issue for larger data sets.
Backup systems may be required to maximise storage
whereas access speed is not so much of an issue
Limited lifespan of SSDs due to limited read/writes may
restrict use in data heavy applications.
Servers will require quick access to data to serve
multiple client machines but will also be extremely
read/write heavy.
AO3
Both suitable for the insurance office but for different
purposes.
SSDs to store operating system and program files will
ensure quicker boot up and loading of programs. MayH446/01 Mark Scheme
The candidate demonstrates a basic knowledge of
magnetic and solid state storage; the material is basic
and contains some inaccuracies. The candidate makes
a limited attempt to apply acquired knowledge and
understanding to the context provided.
The candidate provides a limited discussion which is
narrow in focus. Judgments if made are weak and
unsubstantiated. The information is basic and
communicated in an unstructured way. The information
is supported by limited evidence and the relationship to
the evidence may not be clear.
0 marks
No attempt to answer the question or response is not
worthy of credit.
be useful for both client and servers to store operating
systems
Magnetic hard drives to store large quantities of data
provides reliability and large capacity at small (by
comparison) cost. May be most suitable for storing
large amounts of data on client devices and for backup
systems.
Magnetic tape device may be suitable for backing up
customer data as too slow for use on day-to-day basis.
Use of solid state devices for storing customer data that
is frequently accessed means needing to plan for
replacement of drives when read/write limit reached.
Solid state devices better if used in mobile devices (e.g.
for mobile insurance workers) as relatively small
chance of damage if dropped as no moving parts.
(d) i • Field with a unique value
• CustomerID
2
AO1.2 (1),
AO2.2 (1),
ii • SELECT CustomerID, Surname
• FROM Customer
• WHERE Title="Miss"
• OR Title = "Mrs"
4
AO3.2
1 mark per bullet point.
Data in fields must be in speech marks/apostrophes
Allow speech mark/apostrophe FT for BP 2 and 4
Ignore colons/semicolons
iii • Only one customer entry allowed (because of key
field)
• …so would not be able to add second entry
• Customer data already present/would be repeated
• ….resulting in redundant data/wasted space
• …resulting in inconsistencies should changes be
made
2
AO2.1
Mark in pairs.
Iv • Add in second table
• …for the cars // splitting up cars/customers
• The primary key of customer is used as a field in the
car/vehicle table
• … as a foreign key of cars
• Create one to many relationship. Accept many to
one.
5
AO1.2H446/01 Mark Scheme
Question Answer Mark Guidance
2 (a) i 11100111 1
AO1.2
ii 0110 1111 1
AO1.2
(b) i • Move decimal place 1 place right = 0.1101 to
normalise
• Pad with 0s, mantissa is 011010
• Exponent is 4 / Subtract 1 from exponent…
• New exponent is 3 = 0011
4
AO1.2
ii • move dp 3 places right
• 0110.1
• 6.5
3
AO1.2
Accept conversion of un-normalised number (will result
in same output)
Accept method of using 0.1101 x 2^3
FT required from part (i) if this is done incorrectly.
(c) • Calculating exponent of 6 for first
number/Calculating exponent of 4 for second
number
• Moving binary point correct number of places in
both mantissa to give 0110000.0 and 01010.0
• Addition of 0110000.0 and 01010.0 to give
0111010.0
• Movement of binary point six places to left to
match original mantissa format and give value of
011101
• Calculate exponent in original format to give
value of 0110
5
AO1.2
Alternative:
• Calculation of exponents (6 and 4) // difference
between exponents of 2
• Move first mantissa 2 places left // second mantissa
2 places right to match exponents
• …giving 011.000 + 0.10100 (exp 4) // 0.11000 +
0.00101 (exp 6)
• Correct addition (answer of 011.1010 // 0.111010)
• Final answer normalised (011101 exp 6)
If exponents initially matched to 4, final bullet point
should only be given if answer is normalised. If
exponents matched to 6, answer will already be
normalised.
Ensure that answer is in format described (6 bits for
mantissa 4 bits for exponent) to gain final bullet point.H446/01 Mark Scheme
Question Answer Mark Guidance
3 (a) • HTML defines the structure of a web page
• HTML defines the content of a web page
• Using tags (enclosed in <>)
• CSS defines the style / appearance
• Using selectors such as classes / IDs / etc
• Can be placed within HTML or externally in a file
• Multiple pieces of CSS can be combined (the more
local instances overriding)
4
AO1.1
Do not accept layout/format for HTML as this is too
vague and can be used to describe CSS
(b) • Correct
with close
• href property to correct page
• correct ![]()
tag with src property to correct file
3
AO3.2
(c) • 2.99
• nonUKprice
• numtickets
• return
4
AO3.2
Correct answer only. Penalise spelling if incorrect.
Do not accept £ sign in first bullet point.
(d) i • processing done away from the user’s control/Client
side processing could be altered
• Browser may not support client-side language/
scripting could be turned off
• Booking fee calculation needs to be correct for all
locations
3
AO2.1
ii To the customer any 2x1:
• No need to submit to server and wait for response
2
AO1.2H446/01 Mark Scheme
• Website will work more quickly for user
To the company any 2x1:
• Reduces load on the server
• Will need to spend less on processing
power/bandwidth
(e) i • Web crawler /spider visits site
• Either be selecting it from an existing list or
following a link.
• Records information
• …such as text / metatags / etc
• Records the position of each word within the page
• Storing them in an index
• Follows links to other sites
• Robots.txt file can be used to instruct web crawlers
4
AO1.1
ii • A value between 0 and 1
• Probability that a user will not follow a link
1
AO1.1
iii • Number of links to target site
• PageRank score of those sites (linking inwards)
2
AO1.1H446/01 Mark Scheme
Question Answer Mark Guidance
4 (a) Mark Band 3–High Level (7-9 marks)
The candidate demonstrates a thorough knowledge and
understanding of legislation including the Computer
Misuse Act. The material is generally accurate and
detailed.
The candidate is able to apply their knowledge and
understanding directly and consistently to the context
provided. Evidence/examples will be explicitly relevant
to the explanation.
The candidate provides a thorough discussion which is
well balanced. Evaluative comments are consistently
relevant and well-considered.
There is a well-developed line of reasoning which is
clear and logically structured. The information
presented is relevant and substantiated.
Mark Band 2-Mid Level (4-6 marks)
The candidate demonstrates reasonable knowledge
and understanding legislation including the Computer
Misuse Act; the material is generally accurate but at
times underdeveloped.
The candidate is able to apply their knowledge and
understanding directly to the context provided although
one or two opportunities are missed.
Evidence/examples are for the most part implicitly
relevant to the explanation.
The candidate provides a sound discussion, the
majority of which is focused. Evaluative comments are
for the most part appropriate, although one or two
opportunities for development are missed.
9
AO1.1
(2),
AO1.2
(2),
AO2.1
(2),
AO3.3.
(3)
AO1
Computer Misuse Act is legislation aimed at
criminalising unauthorised access to a computer
system
Three stages:
Unauthorised access to a computer system
Unauthorised access with intent to commit further
offences
Unauthorised modification of computer material
Punishable by up to twelve months in prison and an
unlimited fine.
AO2
Computer users who investigate how systems work
require authorisation in order to not break the Act.
Examples such as changing a social media post on a
friend’s mobile phone potentially breaks all three
sections of the Act.
Investigation of systems can break the Act without
intent, e.g. by changing server logs because of their
actions.
Users must be aware of the Act (as with any other law)
in order to be responsible.
AO3
Material available online (e.g. self study videos) that
explain how systems work and teach without the need
to investigate using unauthorised access.
Investigating systems that you own yourself or have
authorisation to access does not break the law.
Systems are offered to users with strict conditions
attached and investigation is not a legitimate excuse for
breaking the law.
Ethical / white hat hackers will not break this law
because they have authorisation.
Grey and black hat hackers will break Computer Misuse
Act.H446/01 Mark Scheme
There is a line of reasoning presented with some
structure. The information presented is in the most part
relevant and supported by some evidence.
Mark Band 1-Low Level (1-3 marks)
The candidate demonstrates a basic knowledge of
legislation including the Computer Misuse Act; the
material is basic and contains some inaccuracies. The
candidate makes a limited attempt to apply acquired
knowledge and understanding to the context provided.
The candidate provides a limited discussion which is
narrow in focus. Judgments if made are weak and
unsubstantiated. The information is basic and
communicated in an unstructured way. The information
is supported by limited evidence and the relationship to
the evidence may not be clear.
0 marks
No attempt to answer the question or response is not
worthy of credit.H446/01 Mark Scheme
Question Answer Mark Guidance
5 (a) Q ≡ A ∧ B
∧
(C ∨ D)
3
AO1.2
Q ≡ A ∧ B ∧ (C ∨ D)
Accept alternative symbols for AND / OR
e.g. Q = A AND B AND (C OR D)
Brackets must be included for 3rd point
Allow XOR for bullet point 3
Any additional symbols max 2 marks
(b) i • Identification of De Morgan’s and/or double
negation rule
• Correct final answer to give A v B
2
AO2.2
(c) i S = A ⊻ B
C = A ∧ B
2
AO2.1
Accept alternative symbols for AND /XOR
ii • 1 mark for S column
• 1 mark for C column
2
AO2.1
A B S C
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
iii • Logic circuit adds together 2 binary digits / half
adder
4H446/01 Mark Scheme
• S gives sum, C gives carry
• Two half adders can be joined together…
• …with an OR gate
• to form full adder
• 4 full adders can be used to add two four bit
numbers
• Carry out on one joined to carry in on next
AO1.2H446/01 Mark Scheme
Question Answer Mark Guidance
6 (a) i • Temporary storage/memory location…
• …inside the CPU
• Used for a single specific purpose
• Faster access speed than RAM / secondary storage
2
AO1.1
ii • Accumulator checked to see if value held is positive
or zero
• If so, BRANCH carried out / jumps to specified
location.
2
AO1.2
(b) • 2, 2
• 9,0
• 4,0
• 0,3
4
AO2.2
Code finds integer division and remainder.
(c) • Input two numbers into two separate variables /
other suitable data structure
• Correctly calculate integer division
• Correctly calculate remainder
• Print out both
4
AO3.2
Can be completed either by using MOD / DIV or by
using repeated subtraction as in LMC example
(d) Mark Band 3–High Level (9-12 marks)
The candidate demonstrates a thorough knowledge and
understanding of different modes of addressing. The
material is generally accurate and detailed.
The candidate is able to apply their knowledge and
understanding directly and consistently to the context
provided. Evidence/examples will be explicitly relevant
to the explanation.
12
AO1.1
(2),
AO1.2
(2),
AO2.1
(3),
AO3.3.
(5)
AO1
Immediate addressing is where the operand holds the
actual data to be used; no address referenced
Direct addressing is where the operand holds the
address that holds the data to be used.
Indirect addressing is where the operand holds an
address which is where the data to be used is stored
Indexed addressing is where the operand holds an
address which is offset using the Index Register to find
the true address of the data to be used
AO2H446/01 Mark Scheme
The candidate provides a thorough discussion which is
well balanced. Evaluative comments are consistently
relevant and well-considered.
There is a well-developed line of reasoning which is
clear and logically structured. The information
presented is relevant and substantiated.
Mark Band 2-Mid Level (5-8 marks)
The candidate demonstrates reasonable knowledge
and understanding of different modes of addressing;
the material is generally accurate but at times
underdeveloped.
The candidate is able to apply their knowledge and
understanding directly to the context provided although
one or two opportunities are missed.
Evidence/examples are for the most part implicitly
relevant to the explanation.
The candidate provides a sound discussion, the
majority of which is focused. Evaluative comments are
for the most part appropriate, although one or two
opportunities for development are missed.
There is a line of reasoning presented with some
structure. The information presented is in the most part
relevant and supported by some evidence.
Mark Band 1-Low Level (1-4 marks)
The candidate demonstrates a basic knowledge of
different modes of addressing; the material is basic and
contains some inaccuracies. The candidate makes a
limited attempt to apply acquired knowledge and
understanding to the context provided.
The candidate provides a limited discussion which is
narrow in focus. Judgments if made are weak and
unsubstantiated. The information is basic and
Immediate addressing; operand of 27 would refer to the
value 27
Direct addressing; operand of 27 would tell the
processor to fetch the data held at address 27.
Indirect addressing; operand of 27 would tell the
processor to fetch the data held at address 27, which
itself would then be used an address to fetch data from.
Indexed addressing; operand of 27 would be added to
the value of the Index register and this would then be
used as the address to fetch data from.
AO3
Immediate addressing allows simple access to data
with no fetch required, but limited by the data size of the
operand.
Direct addressing allows data to be fetched from
memory. Data can potentially be larger in size that with
immediate addressing but address range limited by size
of operand.
Indirect addressing allows a larger range of addresses
to be accessed as address fetched. However, multiple
fetches required to access data.
Indexed addressing allows the Index register to be
manipulated to access data stored sequentially e.g. in
an array.H446/01 Mark Scheme
communicated in an unstructured way. The information
is supported by limited evidence and the relationship to
the evidence may not be clear.
0 marks
No attempt to answer the question or response is not
worthy of credit.H446/01 Mark Scheme
Question Answer Mark Guidance
7 (a) (i) Stack 1
AO1.1
Correct answer only
(ii) • Input name from user
• Check if stack is full e.g.(top <=5)
• If not, update top pointer
• Correctly push name to index referenced by top
4
AO3.2
Example answer
new = input("enter a name : ")
if top <=5 then
top = top + 1
wNames[top] = new
end if
(b) 1 mark per name inserted in correct place in diagram 4
AO2.1
(ii) • Compare with Kirstie – Zoe is larger so go right
• Compare with Martyn - Zoe is larger so go right
• No right element so stop/not found
3
AO2.2
Allow FT from b(i)
(iii) • Binary tree more efficient than linked list
• Do not need to check every value / tree removes half
values each time
2
AO1.2
Allow reference to big O for second mark.
Linked List O(n), Binary Tree O(log n)
(iv) • Binary tree less efficient than hash table
• Hash table can find data immediately / without
checking other values.
2
AO1.2
Allow reference to big O for second mark.
Binary tree O(log n) Hash table O(1)
(c) (i) • Object – instantiated from class
• Method – action object performs / link to
procedure/functions
• Attribute – value held by object / link to variable
3
AO1.1
(ii) • Class definition statement
• Defining name and attendance attributes
5 One mark per bullet point to 5 maximum.H446/01 Mark Scheme
• Appropriate get methods for name and attendance
that return a value and have no parameter
• Appropriate set methods for name and attendance
that take a parameter
• …that restricts attendance to be 0 to 100.
AO3.2
Example answer
class Customer
private name
private attendance
public function getName()
return name
end function
public function getAttendance()
return attendance
end function
public procedure setName(newName)
name = newName
end procedure
public procedure setAttendance(newAttend)
if newAttend >=0 and newAttend <=100 then
attendance = newAttend
end if
end procedure
end classOCR (Oxford Cambridge and RSA Examinations)
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