Cambridge IGCSE™ and O Level Computer Science
Answers to Computer Systems
Workbook
1 Data representation
1 a 165 = 1 0 1 0 0 1 0 1
b 165 = A 5
2 a 0 1 1 1 0 1 1 0 = 118
b 5 F = 95
c 101011000100=AC4
d 3 E D = (0 0) 1 1 1 1 1 0 1 1 0 1
3 a 800 × 16 = 12 800 MiB
b 12 800/1024 = 12.5 GiB
4 a i 65 = 0 1 0 0 0 0 0 1
ii 97 = 0 1 1 0 0 0 0 1
b i V = 86
ii v = 118
c i 86 = 0 1 0 1 0 1 1 0
ii 118 = 0 1 1 1 0 1 1 0
d Lower-case letters have an ASCII code value which is + 32 when compared to the
equivalent upper-case letter, therefore to convert from an upper-case value, simply place
a '1' in the column with value 32.
M = 77 = 0 1 0 0 1 1 0 1 and m = 77 + 32 = 109 = 0 1 1 …
5 a
0 0 1 0 0 0 0 1
b i
1 0 0 0 0 1 0 0
ii 132
c i R = 27 = 0 0 0 1 1 0 1 1
r = 108 = 0 1 1 0 1 1 0 0
ii M = 22 = 0 0 0 1 0 1 1 0
m = 88 = 0 1 0 1 1 0 0 0
Cambridge IGCSE and O Level Computer Science Teacher's Guide 1
© David Watson and Helen Williams 2021
, Cambridge IGCSE and O Level Computer Science Computer Systems Workbook answers
6 a 44801 = A F 0 1
b 1010 1111 0000 0001
7 Three from:
• memory dumps
• error codes
• MAC addresses
• IP addresses
• HTML colour codes
8
Cambridge IGCSE and O Level Computer Science Teacher's Guide 2
© David Watson and Helen Williams 2021
, Cambridge IGCSE and O Level Computer Science Computer Systems Workbook answers
9 a i Number X D OUTPUT
220 220 128
92 1
64
28 1
32
−4 0
28
16
12 1
8
4 1
4
0 1
2
−2 0
0
1
−1 0
0
0 end
Cambridge IGCSE and O Level Computer Science Teacher's Guide 3
© David Watson and Helen Williams 2021
, Cambridge IGCSE and O Level Computer Science Computer Systems Workbook answers
ii Number X D OUTPUT
73 73 128
−55 0
73
64
9 1
32
−23 0
9
16
−7 0
9
8
1 1
4
−3 0
1
2
−1 0
1
1
0 1
0 end
b The flowchart is converting denary (base 10) numbers into 8-bit binary (base 2) numbers.
10 a i 94
ii 61
b i 10011011
ii 155
This is equal to 94 + 61 in denary.
Cambridge IGCSE and O Level Computer Science Teacher's Guide 4
© David Watson and Helen Williams 2021
Answers to Computer Systems
Workbook
1 Data representation
1 a 165 = 1 0 1 0 0 1 0 1
b 165 = A 5
2 a 0 1 1 1 0 1 1 0 = 118
b 5 F = 95
c 101011000100=AC4
d 3 E D = (0 0) 1 1 1 1 1 0 1 1 0 1
3 a 800 × 16 = 12 800 MiB
b 12 800/1024 = 12.5 GiB
4 a i 65 = 0 1 0 0 0 0 0 1
ii 97 = 0 1 1 0 0 0 0 1
b i V = 86
ii v = 118
c i 86 = 0 1 0 1 0 1 1 0
ii 118 = 0 1 1 1 0 1 1 0
d Lower-case letters have an ASCII code value which is + 32 when compared to the
equivalent upper-case letter, therefore to convert from an upper-case value, simply place
a '1' in the column with value 32.
M = 77 = 0 1 0 0 1 1 0 1 and m = 77 + 32 = 109 = 0 1 1 …
5 a
0 0 1 0 0 0 0 1
b i
1 0 0 0 0 1 0 0
ii 132
c i R = 27 = 0 0 0 1 1 0 1 1
r = 108 = 0 1 1 0 1 1 0 0
ii M = 22 = 0 0 0 1 0 1 1 0
m = 88 = 0 1 0 1 1 0 0 0
Cambridge IGCSE and O Level Computer Science Teacher's Guide 1
© David Watson and Helen Williams 2021
, Cambridge IGCSE and O Level Computer Science Computer Systems Workbook answers
6 a 44801 = A F 0 1
b 1010 1111 0000 0001
7 Three from:
• memory dumps
• error codes
• MAC addresses
• IP addresses
• HTML colour codes
8
Cambridge IGCSE and O Level Computer Science Teacher's Guide 2
© David Watson and Helen Williams 2021
, Cambridge IGCSE and O Level Computer Science Computer Systems Workbook answers
9 a i Number X D OUTPUT
220 220 128
92 1
64
28 1
32
−4 0
28
16
12 1
8
4 1
4
0 1
2
−2 0
0
1
−1 0
0
0 end
Cambridge IGCSE and O Level Computer Science Teacher's Guide 3
© David Watson and Helen Williams 2021
, Cambridge IGCSE and O Level Computer Science Computer Systems Workbook answers
ii Number X D OUTPUT
73 73 128
−55 0
73
64
9 1
32
−23 0
9
16
−7 0
9
8
1 1
4
−3 0
1
2
−1 0
1
1
0 1
0 end
b The flowchart is converting denary (base 10) numbers into 8-bit binary (base 2) numbers.
10 a i 94
ii 61
b i 10011011
ii 155
This is equal to 94 + 61 in denary.
Cambridge IGCSE and O Level Computer Science Teacher's Guide 4
© David Watson and Helen Williams 2021
