AQA A-LEVEL COMPUTER SCIENCE PAPER2
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
Tuesday 9 June 2020 Morning Time allowed: 2 hours 30 minutes
Materials
For this paper you must have:
• a calculator. For Examiner’s Use
Instructions Question Mark
• Use black ink or black ball-point pen. 1
• Fill in the boxes at the top of this page. 2
• Answer all questions.
3
• You must answer the questions in the spaces provided. Do not write outside
the box around each page or on blank pages. 4
• If you need extra space for your answer(s), use the lined pages at the end of 5
this book. Write the question number against your answer(s).
6
• Do all rough work in this book. Cross through any work you do not want to
be marked. 7
8
Information
9
• The marks for questions are shown in brackets.
• The maximum mark for this paper is 100. 10
11
Advice
• In some questions you are required to indicate your answer by completely TOTAL
shading a lozenge alongside the appropriate answer as shown.
• If you want to change your answer you must cross out your original answer as
shown.
• If you wish to return to an answer previously crossed out, ring the answer
you now wish to select as shown.
*Jun207517201*
IB/G/Jun20/E16 7517/2
, 2
Do not write
outside the
Answer all questions. box
0 1 . 1 A sound has been sampled and recorded. The sound was sampled for 1 minute and
40 seconds at a sample rate of 8000 Hz with a 16-bit sample resolution.
A sample rate of 1 Hz means that one sample has been taken every second.
Calculate the minimum amount of storage space, in bytes, needed to store the
sampled sound.
You should show your working.
[2 marks]
Answer
0 1 . 2 An analogue to digital converter (ADC) was used during the sampling process.
Explain the principles of operation of an ADC.
[2 marks]
4
*02*
IB/G/Jun20/7517/2
, 3
Do not write
outside the
0 2 Questions 02.2, 02.3, 02.4 and 02.5 use a normalised floating point representation box
with a 7-bit mantissa and a 5-bit exponent, both stored using two’s complement.
0 2 . 1 Non-integer values such as -1.65 and 23/1068 can be represented by a computer
using a fixed point or a floating point system.
State one advantage of using a floating point system over a fixed point system and
one advantage of using a fixed point system over a floating point system.
You should assume that the two systems use the same number of bits to store a
value.
[2 marks]
Advantage of floating point
Advantage of fixed point
0 2 . 2 The following is a floating point representation of a number:
Calculate the decimal equivalent of the number.
Express your answer to at least four decimal places or as a fraction. You should
show your working.
[2 marks]
Answer
Turn over ►
*03*
IB/G/Jun20/7517/2
, 4
Do not write
outside the
Questions 02.2, 02.3, 02.4 and 02.5 use a normalised floating point representation box
with a 7-bit mantissa and a 5-bit exponent, both stored using two’s complement.
0 2 . 3 Write the normalised floating point representation of the decimal value 1632 in the
boxes below.
You should show your working.
[3 marks]
Answer
*04*
IB/G/Jun20/7517/2
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
Tuesday 9 June 2020 Morning Time allowed: 2 hours 30 minutes
Materials
For this paper you must have:
• a calculator. For Examiner’s Use
Instructions Question Mark
• Use black ink or black ball-point pen. 1
• Fill in the boxes at the top of this page. 2
• Answer all questions.
3
• You must answer the questions in the spaces provided. Do not write outside
the box around each page or on blank pages. 4
• If you need extra space for your answer(s), use the lined pages at the end of 5
this book. Write the question number against your answer(s).
6
• Do all rough work in this book. Cross through any work you do not want to
be marked. 7
8
Information
9
• The marks for questions are shown in brackets.
• The maximum mark for this paper is 100. 10
11
Advice
• In some questions you are required to indicate your answer by completely TOTAL
shading a lozenge alongside the appropriate answer as shown.
• If you want to change your answer you must cross out your original answer as
shown.
• If you wish to return to an answer previously crossed out, ring the answer
you now wish to select as shown.
*Jun207517201*
IB/G/Jun20/E16 7517/2
, 2
Do not write
outside the
Answer all questions. box
0 1 . 1 A sound has been sampled and recorded. The sound was sampled for 1 minute and
40 seconds at a sample rate of 8000 Hz with a 16-bit sample resolution.
A sample rate of 1 Hz means that one sample has been taken every second.
Calculate the minimum amount of storage space, in bytes, needed to store the
sampled sound.
You should show your working.
[2 marks]
Answer
0 1 . 2 An analogue to digital converter (ADC) was used during the sampling process.
Explain the principles of operation of an ADC.
[2 marks]
4
*02*
IB/G/Jun20/7517/2
, 3
Do not write
outside the
0 2 Questions 02.2, 02.3, 02.4 and 02.5 use a normalised floating point representation box
with a 7-bit mantissa and a 5-bit exponent, both stored using two’s complement.
0 2 . 1 Non-integer values such as -1.65 and 23/1068 can be represented by a computer
using a fixed point or a floating point system.
State one advantage of using a floating point system over a fixed point system and
one advantage of using a fixed point system over a floating point system.
You should assume that the two systems use the same number of bits to store a
value.
[2 marks]
Advantage of floating point
Advantage of fixed point
0 2 . 2 The following is a floating point representation of a number:
Calculate the decimal equivalent of the number.
Express your answer to at least four decimal places or as a fraction. You should
show your working.
[2 marks]
Answer
Turn over ►
*03*
IB/G/Jun20/7517/2
, 4
Do not write
outside the
Questions 02.2, 02.3, 02.4 and 02.5 use a normalised floating point representation box
with a 7-bit mantissa and a 5-bit exponent, both stored using two’s complement.
0 2 . 3 Write the normalised floating point representation of the decimal value 1632 in the
boxes below.
You should show your working.
[3 marks]
Answer
*04*
IB/G/Jun20/7517/2
