Cambridge IGCSE™ and O Level Computer Science
Practice Paper 1B – Computer Systems
Time allowed: 2 hours 15 minutes
Maximum number of marks:
100
Answer all questions
The security code to unlock a safe is composed of six characters. The code is formed from the ten digits 0 to
9 and the six letters A to F. The present security code is:
O
1
F
F
1
C
E
a) i)
Each character in the security code is a hexadecimal number. Write down the 4-bit binary
equivalent of each of the six characters:
O
F
F
1
C
E
[2]
a) ii)
Explain why the security code, OFF1CE, is not a very secure choice.
[1]
b) i)
Convert the denary number, 45, into an 8-bit binary number.
[1]
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b)
ii)
format.
Convert the denary number, –83, into an 8-bit binary number in two’s complement
[1]
b)
iii)
Carry out the sum, 45 + (–83), and comment on your result.
[2]
c)
i)
Convert the denary number, 943, into a 3-digit hexadecimal number.
[2]
c)
ii)
Describe one use of the hexadecimal system.
[2]
2
a) i)
Give two advantages of using an automated system.
1
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[2]
a)
ii)
Give two disadvantages of using an automated system.
1
2
[2]
The diagram below shows an industrial process which is being used to produce a vaccine. There are two
stages in the process which involve the use of a microprocessor, interfaces, sensors, actuators (to operate
stirrers and valves), and a database.
b)
Complete the diagram by naming the parts (1) to (5).
(1)
Process 1
(3)
(2)
(4)
(5)
(1)
Process 2
(3)
(2)
1
2
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3
4
5
[3]
One example of an automated system is the control of entry and exit to a public car park. Cameras take a
photograph of the front of a car as it approaches the entry barrier. At the exit barrier, a second camera
takes a photograph of the front of the car. The exit barrier will only be raised if the correct parking fee has
been paid. Describe how sensors, cameras, actuators and a microprocessor would be used to do the
following:
c)
i)
Control the correct raising and lowering of the entry and exit barriers for a car.
[4]
c)
ii)
Ensure that the car approaching the exit barrier has paid the correct parking fee
before raising the barrier.
[3]
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a) i)
The terms AI (artificial intelligence) and machine learning are shown on the left in the
diagram below. Four statements are shown on the right.
By drawing lines, connect each term to the statements that correctly apply.
[4]
a)
ii)
Autonomous vehicles (such as cars, buses and vans) are undergoing rapid
development. Define the term autonomous.
[1]
b)
ii)
Give two advantages of using autonomous vehicles.
1
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[2]
b)
iii)
Give two disadvantages of using autonomous vehicles.
1
2
[2]
c)
Six statements about expert systems are made in the table below. Put a tick (✓) in the
correct column to indicate whether the statement refers to a knowledge base, rules base or
inference engine.
Statements
Knowledge Rules
base
base
Inference
engine
Acts like a search engine by examining
knowledge and data to see if it matches the
queries
Repository of facts; a collection of objects and
attributes
A set of inference rules
Uses inference rules to draw conclusions
Follows logical thinking; often uses a set of “IF”
statements to draw a logical conclusion
Stores all the knowledge about an area of
expertise obtained from a number of sources
[6]
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a) i)
Blockchaining is used by cryptocurrency transactions. Explain what is meant by a
cryptocurrency.
[1]
a) ii)
When a new cryptocurrency transaction takes place, a new block is created. Name three
items found in a typical cryptocurrency block.
1
2
3
[3]
b)
Blockchaining helps to prevent data tampering by cybercriminals. Three other methods
used by cybercriminals to illegally gain personal data are phishing, pharming and Trojan horses.
Describe each of these three types of cyber security threats.
Phishing:
Pharming:
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Trojan horse:
[6]
5
Name the five computer terms being described below.
a) i)
Program that supplies moving and still images on a monitor after a period of inactivity by a
computer:
a) ii)
Software that communicates with the operating system and translates data into a format
understood by a peripheral device, for example, a printer:
a) iii)
Signal sent from a device or software to a microprocessor/CPU causing it to temporarily
halt what it is doing:
a) iv)
Area of memory which holds data temporarily (for example, data being sent to a printer)
allowing a processor to carry out other tasks:
a) v)
On starting up a computer, part of the operating system is loaded into RAM which is
handled by the BIOS:
[5]
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Human computer interfaces are usually called CLI or GUI.
b)
i)
Explain these two terms:
CLI:
GUI:
[2]
b)
ii)
Give two advantages and two disadvantages of using CLI.
Advantage 1:
Advantage 2:
[2]
Disadvantage 1:
Disadvantage 2:
[2]
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a) The Fetch-Decode-Execute cycle is split up into six steps. These steps are given below in a table, but
are not written in the correct order. By writing the numbers 1 to 6 in the left column, put each step into
its correct order.
Order
Steps
Contents at the memory location contained in the MAR are then copied
temporarily into the MDR.
The value in PC is then incremented by 1, so that it now points to the next
instruction which needs to be fetched.
The PC contains the address of the memory location of the next instruction which
is about to be fetched.
The contents of the MDR are then copied and placed into the CIR.
The instruction is finally decoded and then executed by sending out signals (via the
control bus) to the various components of the computer system.
This address is then copied from the PC to the MAR using the address bus.
[5]
b)
Four types of address were mentioned in part a). Explain the function of these four
registers.
PC:
MAR:
MDR:
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CIR:
[4]
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a) i)
Smartphones and tablets use different types of touchscreen technology. Look at the
following three diagrams of touchscreen technology. Write down the name of the touchscreen
technology being depicted in each case:
Type of touchscreen technology:
Type of touchscreen technology:
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Type of touchscreen technology:
[3]
a)
ii)
Give one advantage of each type of touchscreen technology shown in part a) i).
Touchscreen technology
Advantage
[3]
b)
3D printers make use of direct 3D printing or binder 3D printing. Compare both types of 3D
printing methods.
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[2]
c) Inkjet and laser printers are used in the office to carry out many tasks. Describe the differences in
technology used by both types of printer.
[3]
8
a) The following diagram shows the name of two types of projector used in giving presentations. Six
statements about projectors are shown on the right. By drawing lines indicate which statements refer
to each type of named projector.
[6]
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b)
A manager is using a DLP projector to give a presentation. She is using a laptop to interface
with the projector. All the files she is using are stored on the cloud.
Describe three advantages to storing important files on the cloud.
1:
2:
3:
[3]
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a) Explain the differences between random access memory (RAM) and read-only memory (ROM).
[3]
b)
A computer is using virtual memory. Complete the paragraph below using the following
terms. Each term could be used once, more than once or not at all.
o increasing
o latency
o physical memory
o random access memory
o read only memory
o reducing
o redundancy
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o
o
o
o
o
swap space
thrashing
thrash point
unlimited memory
virtual memory
When using virtual memory, RAM is the ………………………………… and RAM plus swap space on HDD is known
as the ……………………..….Virtual memory gives the illusion of ………………………………………. being available to
the user. One drawback when using HDD occurs when there is a high rate of head movements; this is
known as ………………………………..This can be reduced by increasing the size of …………………………... or by
………………………………… the number of programs running.
[6]
c)
Give two benefits of using virtual memory.
[2]
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