COMPUTER SCIENCE
REINFORCEMENT WORKSHEET IX
Total Marks 50
1 (a) (i) Convert the following two hexadecimal numbers into binary:
FA7
D3E
FA7
D3E
[4]
(ii) Now perform the AND (logic) operation on each corresponding pair of binary bits in the
two numbers from part (i).
[2]
(iii) Convert your answer in part (ii) into hexadecimal.
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[2]
(b) (i) The following code shows HTML ‘tag’ pairs on either side of the text stating the colour
that each creates.
<font color “ # F F 0 0 0 0 “ > RED </font>
<font color “ # 0 0 F F 0 0 “ > GREEN </font>
<font color “ # 0 0 0 0 F F “ > BLUE </font>
<font color “ # X “ > YELLOW </font>
<font color “ # Y “ > MAGENTA </font>
<font color “ # Z “ > CYAN </font>
Yellow is a combination of red and green, magenta a combination of red and blue and
cyan a combination of green and blue.
State what 6-digit hexadecimal values should replace X, Y and Z in the above code.
X . .......................................................................................................................................
Y . .......................................................................................................................................
Z . .......................................................................................................................................
[3]
(ii) Describe how other colours, such as a darker shade of blue, are created.
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[2]
(c) 1A – 16 – C5 – 22 – FF – FF is an example of a MAC address.
(i) Identify what the first six and last six hexadecimal digits represent.
First six digits . ..................................................................................................................
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Last six digits . . . . .............................................................................................................
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[2]
(ii) State why MAC addresses are used.
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[1]
2 (a) Complete the truth tables and name the single logic gate that could replace each logic circuit:
(i)
A Working space
A B X
X
B
0 0
0 1
1 0
1 1
Single logic gate ............................................................................................................[3]
(ii)
A Working space
A B X
X 0 0
0 1
B 1 0
1 1
Single logic gate ............................................................................................................[3]
(b) (i) Draw a logic circuit to represent the following logic statement:
X = 1 if (A = 1 AND B = 1) OR ( (B = NOT 1) AND C = 1)
B X
[4]
(ii) Complete the truth table for the logic statement in part (b)(i).
Working space
A B C X
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
[4]
3 The conditions in a fish tank are being controlled using sensors and a microprocessor. To keep
the fish healthy, the temperature must be at 25°C and the oxygen content needs to be 20 ppm
(parts per million). The tank contains a heater and an oxygen inlet controlled by a valve.
heater oxygen supply
sensor A sensor B
microprocessor
(a) Describe how the sensors and the microprocessor are used to maintain the
correct conditions in the fish tank.
[4]
(b) Five sensors and five applications are shown below.
Draw a line to link each sensor to its most appropriate application.
Sensor Application
Light
Monitor the pollution levels in a river
sensor
Moisture Control the switching off and on of
sensor street lights
Gas Detect intruders breaking into a
sensor building
pH Monitor the amount of water left in
sensor clothes in a dryer
Pressure Monitor acidity levels in the soil in a
sensor greenhouse
[4]
4 The majority of mobile phones use touch screens. Three common technologies are used by
different mobile phone manufacturers.
Choose one of the following mobile phone technologies:
• resistive
• capacitive
• infrared
Chosen technology ..........................................................................................................................
(i) Describe how your chosen technology works to allow a user to make selections by touching
the screen.
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(ii) Give one benefit and one drawback of your chosen technology when used on mobile phone
touch screens.
Benefit
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Drawback
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[2]
5 The steps to print a document using a laser printer are shown in the table below.
Put each step in the correct order. The first step has been done for you.
Step Order
As the printing drum rotates, a laser scans across it; this removes the
positive charge in certain areas
The printing drum is coated in positively-charged toner; this then sticks to the
negatively-charged parts of the printing drum
The paper goes through a fuser which melts the toner so it fixes permanently
to the paper
The printer driver ensures that the data is in a format that the laser printer
can understand 1
A negatively-charged sheet of paper is then rolled over the printing drum
Data is then sent to the laser printer and stored temporarily in the printer
buffer
The toner on the printing drum is now transferred to the paper to reproduce
the required text and images
The printing drum is given a positive charge
Negatively-charged areas are then produced on the printing drum; these
match exactly with the text and images to be printed
[8]
