Cambridge International AS & A Level

* 4 1 5 8 9 4 4 3 1 5 *

COMPUTER SCIENCE 9618/13

Paper 1 Theory Fundamentals May/June 2022

1 hour 30 minutes

You must answer on the question paper.

No additional materials are needed.

INSTRUCTIONS
● Answer all questions.
● Use a black or dark blue pen.
● Write your name, centre number and candidate number in the boxes at the top of the page.
● Write your answer to each question in the space provided.
● Do not use an erasable pen or correction fluid.
● Do not write on any bar codes.
● You may use an HB pencil for any diagrams, graphs or rough working.
● Calculators must not be used in this paper.

INFORMATION
● The total mark for this paper is 75.
● The number of marks for each question or part question is shown in brackets [ ].
● No marks will be awarded for using brand names of software packages or hardware.

This document has 16 pages. Any blank pages are indicated.

DC (PQ/CGW) 301925/5
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1 Text and numbers are examples of data stored in a computer.

(a) A character set is used to represent characters in a computer.

(i) Describe what is meant by a character set.

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(ii) Identify two character sets and state one difference between them.

Character set 1 ..................................................................................................................

Character set 2 ..................................................................................................................

Difference ..........................................................................................................................

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(iii) Describe how lossless compression can be used to reduce the file size of a text file.

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(iv) Explain why lossy compression should not be used on a text file.

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(b) A computer can represent numerical data in different forms.

Complete the table by writing the answer to each statement.

Statement Answer

The hexadecimal value 11 represented in denary

The smallest denary number that can be represented

by an unsigned 8-bit binary integer
The denary number 87 represented in Binary Coded
Decimal (BCD)

The denary number 240 represented in hexadecimal

The denary number –20 represented in 8-bit two’s

complement binary
[5]

Working space

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2 (a) The Fetch-Execute (F-E) cycle is represented in register transfer notation.

Describe each of the given steps.

Step Description

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PC [PC] + 1
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MDR [[MAR]]
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MAR [PC]
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[3]

(b) Explain how interrupts are handled during the F-E cycle.

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3 (a) The table shows part of the instruction set for a processor. The processor has one general
purpose register, the Accumulator (ACC).

Instruction
Explanation
Opcode Operand
LDM #n Immediate addressing. Load the number n to ACC
Direct addressing. Load the contents of the location at the
LDD <address>
given address to ACC
Indirect addressing. The address to be used is at the given
LDI <address>
address. Load the contents of this second address to ACC
<address> can be an absolute or symbolic address
# denotes a denary number, e.g. #123

The current contents of main memory are:

Address
100 101
101 67
102 104
103 100
104 68

Complete the table by writing the value stored in the accumulator after the execution of each
instruction.

Instruction Accumulator
LDM #103

LDD 102

LDI 103

[3]

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(b) The instructions in part (a) are examples of the data movement group.

Describe two other instruction groups.

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(c) The table shows part of the instruction set for a processor. The processor has one general
purpose register, the Accumulator (ACC).

Instruction
Explanation
Opcode Operand
AND Bn Bitwise AND operation of the contents of ACC with the operand
XOR Bn Bitwise XOR operation of the contents of ACC with the operand
OR Bn Bitwise OR operation of the contents of ACC with the operand
B denotes a binary number, e.g. B01001010

The binary value 00111101 is stored in the memory address 200.

Each instruction in the diagram is performed on the data in memory address 200.

Draw one line from each instruction to its correct result.

Instruction Result

01111101

XOR B11110000
00111101

OR B01010101 11111111

AND B11111111 11000010

11001101

[3]

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4 A computer has system software including an operating system.

(a) Describe the key management tasks of an operating system.

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(b) Utility software is a type of system software.

(i) Describe the purpose of back-up software and defragmentation software.

Back-up software ..............................................................................................................

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Defragmentation software .................................................................................................

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(ii) Give one other example of utility software.

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5 A company wants to store data about its employees in a computer system. The owner of the
company wants to ensure the security and integrity of the data.

(a) (i) State why data needs to be kept secure.

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(ii) One way the data stored in a computer can be kept secure is by using back-up software.

Give two other ways the data stored in a computer can be kept secure.

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(b) The data about the employees is currently stored on paper. The data needs to be transferred
into the computer system.

Data validation and verification are used to help maintain the integrity of the data.

(i) Identify and describe one method of data verification that can be used when transferring
the data from paper to the computer.

Method ..............................................................................................................................

Description ........................................................................................................................

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(ii) The company needs to transfer the date of birth of each employee into the computer
system.

Give one example of how each of the following data validation rules can be used to
validate the date of birth when it is entered into the system.

Range check .....................................................................................................................

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Presence check .................................................................................................................

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Length check .....................................................................................................................

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(iii) Explain why the data in the system may not be correct even after validating and verifying
the data.

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6 A relational database, TECHNOLOGY, stores data about the staff in a company and the computer
devices used by the staff.

The database has the following tables:

STAFF(StaffID, FirstName, LastName, DateOfBirth, JobTitle)

DEVICE(DeviceID, Type, DatePurchased, StaffID)

(a) Describe the relationship between the two tables. Refer to the primary and foreign keys in
your answer.

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(b) The database uses a Data Definition Language (DDL) and Data Manipulation Language
(DML).

(i) Complete the SQL script to return the number of devices stored in the database for the
staff member with the first name ‘Ali’ and last name ‘Khan’.

SELECT .............................................................. (STAFF.StaffID)

FROM ..............................................................

INNER JOIN DEVICE

.............................................................. STAFF.StaffID = DEVICE.StaffID

WHERE STAFF.FirstName = 'Ali'

.............................................................. STAFF.LastName = 'Khan';

[4]

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(ii) The table DEVICE needs a new attribute to store whether the device has been returned
by the staff member, or not.

Write a Structured Query Language (SQL) script to insert the new attribute into the table
DEVICE.

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(c) The database is in Third Normal Form (3NF).

Complete the table by describing the three normal forms.

Normal Form Description

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First Normal Form (1NF)
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Second Normal Form (2NF)
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Third Normal Form (3NF)
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7 (a) Write the logic expression for the following logic circuit.

B
X

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(b) Complete the truth table for the following logic expression:

X = (A NAND B) OR (A AND NOT C)

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
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8 A company uses cloud computing.

(a) Define cloud computing.

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(b) State what is meant by a public cloud and a private cloud.

Public cloud ..............................................................................................................................

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Private cloud .............................................................................................................................

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(c) Give two benefits and one drawback of using cloud computing.

Benefit 1 ...................................................................................................................................

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Benefit 2 ...................................................................................................................................

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Drawback ..................................................................................................................................

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[3]

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© UCLES 2022 9618/13/M/J/22