Please write clearly in block capitals.
Centre number Candidate number
Surname
Forename(s)
Candidate signature
I declare this is my own work.
A-level
COMPUTER SCIENCE
Paper 2
Wednesday 17 June 2026 Morning Time allowed: 2 hours 30 minutes
Materials
For this paper you must have: For Examiner’s Use
• a calculator. Question Mark
Instructions
• Use black ink or black ball-point pen.
• Fill in the boxes at the top of this page.
• Answer all questions.
• You must answer the questions in the spaces provided. Do not write outside
the box around each page or on blank pages.
• If you need extra space for your answer(s), use the lined pages at the end of
this book. Write the question number against your answer(s).
• Do all rough work in this book. Cross through any work you do not want to
be marked.
Information
• The marks for questions are shown in brackets.
• The maximum mark for this paper is 100.
Advice 3
• In some questions you are required to indicate your answer by completely
14
shading a lozenge alongside the appropriate answer as shown.
• If you want to change your answer you must cross out your original answer TOTAL
as shown.
• If you wish to return to an answer previously crossed out, ring the answer
you now wish to select as shown.
*JUN *
IB/G/Jun26/G4007/V8 7517/2
, 2
Do not write
outside the
Answer all questions. box
0 1 . 1 Describe how a number can be converted from decimal to hexadecimal.
[3 marks]
0 1 . 2 MAC addresses are hardware addresses that are used to uniquely identify devices
connected to a network.
They are usually displayed in hexadecimal, for example:
12-A0-54-B1-28-4C
State one reason why MAC addresses are displayed in hexadecimal instead
of binary.
[1 mark]
4
*02*
IB/G/Jun26/7517/2
, 3
Do not write
outside the
0 2 . 1 A message has been encrypted using the Vernam cipher and the key HOT box
The ciphertext produced was in binary.
Conversion between letters and their equivalent binary patterns was carried out using
a 5-bit code called the Baudot–Murray code. The version of the Baudot–Murray code
used for conversion is shown in Figure 1.
Figure 1
Letter Encoding Letter Encoding
A 11000 N 00110
B 10011 O 00011
C 01110 P 01101
D 10010 Q 11101
E 10000 R 01010
F 10110 S 10100
G 01011 T 00001
H 00101 U 11100
I 01100 V 01111
J 11010 W 11001
K 11110 X 10111
L 01001 Y 10101
M 00111 Z 10001
Decrypt the ciphertext to work out what the original plaintext message was.
Express the plaintext as letters.
Show your working.
[2 marks]
Answer
Turn over ►
*03*
IB/G/Jun26/7517/2
, 4
Do not write
outside the
0 2 . 2 The ciphertext CXHB was produced from some plaintext using the Caesar cipher and box
an unknown key.
Figure 2 shows the alphabet and Figure 3 shows five words.
Figure 2
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Figure 3
COUNT
FAKE
SNOW
MORE
TOYS
How many of the words in Figure 3 could have been the plaintext that produced the
ciphertext CXHB using the Caesar cipher?
[1 mark]
0 2 . 3 The Caesar and Vernam ciphers are symmetric ciphers.
Describe how a symmetric cipher differs from an asymmetric cipher.
[1 mark]
*04*
IB/G/Jun26/7517/2
Centre number Candidate number
Surname
Forename(s)
Candidate signature
I declare this is my own work.
A-level
COMPUTER SCIENCE
Paper 2
Wednesday 17 June 2026 Morning Time allowed: 2 hours 30 minutes
Materials
For this paper you must have: For Examiner’s Use
• a calculator. Question Mark
Instructions
• Use black ink or black ball-point pen.
• Fill in the boxes at the top of this page.
• Answer all questions.
• You must answer the questions in the spaces provided. Do not write outside
the box around each page or on blank pages.
• If you need extra space for your answer(s), use the lined pages at the end of
this book. Write the question number against your answer(s).
• Do all rough work in this book. Cross through any work you do not want to
be marked.
Information
• The marks for questions are shown in brackets.
• The maximum mark for this paper is 100.
Advice 3
• In some questions you are required to indicate your answer by completely
14
shading a lozenge alongside the appropriate answer as shown.
• If you want to change your answer you must cross out your original answer TOTAL
as shown.
• If you wish to return to an answer previously crossed out, ring the answer
you now wish to select as shown.
*JUN *
IB/G/Jun26/G4007/V8 7517/2
, 2
Do not write
outside the
Answer all questions. box
0 1 . 1 Describe how a number can be converted from decimal to hexadecimal.
[3 marks]
0 1 . 2 MAC addresses are hardware addresses that are used to uniquely identify devices
connected to a network.
They are usually displayed in hexadecimal, for example:
12-A0-54-B1-28-4C
State one reason why MAC addresses are displayed in hexadecimal instead
of binary.
[1 mark]
4
*02*
IB/G/Jun26/7517/2
, 3
Do not write
outside the
0 2 . 1 A message has been encrypted using the Vernam cipher and the key HOT box
The ciphertext produced was in binary.
Conversion between letters and their equivalent binary patterns was carried out using
a 5-bit code called the Baudot–Murray code. The version of the Baudot–Murray code
used for conversion is shown in Figure 1.
Figure 1
Letter Encoding Letter Encoding
A 11000 N 00110
B 10011 O 00011
C 01110 P 01101
D 10010 Q 11101
E 10000 R 01010
F 10110 S 10100
G 01011 T 00001
H 00101 U 11100
I 01100 V 01111
J 11010 W 11001
K 11110 X 10111
L 01001 Y 10101
M 00111 Z 10001
Decrypt the ciphertext to work out what the original plaintext message was.
Express the plaintext as letters.
Show your working.
[2 marks]
Answer
Turn over ►
*03*
IB/G/Jun26/7517/2
, 4
Do not write
outside the
0 2 . 2 The ciphertext CXHB was produced from some plaintext using the Caesar cipher and box
an unknown key.
Figure 2 shows the alphabet and Figure 3 shows five words.
Figure 2
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Figure 3
COUNT
FAKE
SNOW
MORE
TOYS
How many of the words in Figure 3 could have been the plaintext that produced the
ciphertext CXHB using the Caesar cipher?
[1 mark]
0 2 . 3 The Caesar and Vernam ciphers are symmetric ciphers.
Describe how a symmetric cipher differs from an asymmetric cipher.
[1 mark]
*04*
IB/G/Jun26/7517/2
