AQA GCSE COMPUTER SCIENCE 8525/2
COMPUTER SCIENCE PAPER 2 COMPUTING
CONCEPTS ASSESSMENT PAPER
(AUTHENTIC MARKING SCHEME ATTACHED)
GCSE
COMPUTER SCIENCE
Paper 2 - Computing concepts
Specimen Assessment Materials Time allowed: 1 hour 45 minutes
Materials
• There are no additional materials required for this paper.
• You must not use a calculator.
Instructions
• Use black ink or black ball-point pen. Use pencil only for drawing.
• Answer all questions.
• You must answer the questions in the spaces provided.
• Do all rough work in this book.
• Cross through any work you do not want to be marked.
Information
• The total number of marks available for this paper is 90.
Advice
For the multiple-choice questions, completely fill in the lozenge alongside the appropriate answer.
CORRECT METHOD WRONG METHODS
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.
8525/2
, 2
Do not write
outside the
box
Answer all questions.
0 1 A bit pattern is shown in Figure 1.
Figure 1
01001110
0 1 . 1 Convert the bit pattern shown in Figure 1 into decimal.
[1 mark]
0 1.2 Convert the bit pattern shown in Figure 1 into hexadecimal.
[2 marks]
Answer:
, 3
Do not write
outside the
0 1 . 3 A student’s answer to the question “Why is hexadecimal often used instead of box
binary?” is shown in Figure 2.
Figure 2
Because it uses fewer digits it will take up less space in a computer’s memory.
Explain why the student’s answer is incorrect.
[2 marks]
0 1 . 4 Explain how a binary number can be multiplied by 8 by shifting bits.
[2 marks]
ASCII (American Standard Code for Information Interchange) is a coding system that
can be used to represent characters. In ASCII the character A is represented by the
numeric code 65.
0 1 . 5 Shade one lozenge to indicate which character is represented by the numeric code
70.
[1 mark]
A E
B F
C f
D 6
E e
Turn over ►
Turn over ►
, 4
Do not write
outside the
0 1.6 Unicode is an alternative to the ASCII coding system. box
State two advantages of using Unicode to represent characters instead of using
ASCII.
[2 marks]
When data is stored in a computer it is often compressed. One method that can be
used to compress text data is Huffman coding. To produce a Huffman code each
character in a piece of text is placed in a tree, with its position in the tree
determined by how often the character was used in the piece of text.
A Huffman tree for the text ZOE SAW A ZEBRA AT THE ZOO is shown
in Figure 3.
Figure 3
SPACE
A Z E O
S T
R H B W
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