CAMEROON PAST GCE ORDINARY LEVEL COMPUTER SCIENCE … · 2018. 5. 8. · Computer Science at the Ordinary level consist of 3 papers namely: Paper 1, 2 and 3. Paper 2 accounts for

CAMEROON PAST GCE ORDINARY LEVEL COMPUTER SCIENCE PAPER 2 QUESTIONS

& ANSWERS FROM 2016 – 2018

Compiled By:

GAMO NANA

Credits to:

gamonana.wordpress.com

www.cameroongcerevision.com

www.thebigbrain.com

August 2019

gamonana.wordpress.com

http://www.cameroongcerevision.com/

http://www.thebigbrain.org/

Table of Contents STRUCTURE OF THE EXAM..........................................................................................................3

1. QUESTION SECTION .............................................................................................................4

1.1. JUNE 2016 .................................................................................................................... .5

1.2. JUNE 2017 ....................................................................................................................10

1.3. JUNE 2018 ....................................................................................................................15

2. ANSWER SECTION ................................................................................................................20

2.1. JUNE 2016 ....................................................................................................................21

2.2. JUNE 2017 ....................................................................................................................31

2.3. JUNE 2018 ....................................................................................................................44

SOME TIPS WHEN WRITING THE EXAM ....................................................................................54

2

STRUCTURE OF THE EXAM Computer Science at the Ordinary level consist of 3 papers namely: Paper 1, 2 and 3.

Paper 2 accounts for 30% of the overall mark. It consists of 7 essay questions of which you are

required to answer 5. Section A of this paper comprises of two compulsory questions while

Section B will require you to answer any three out of five questions.

This paper has a duration of 2hrs.

This book would help you get familiar with the type of questions. It will help you to tackle the

exam with ease.

Disclaimer: The answers provided here are not the official marking guide. They express a

personal point of view. Feel free to contribute or report a problem at

gamonana.wordpress.com/contact

You are free to reproduce and share this book without the author’s permission.

3

1. QUESTION SECTION

4

1.1. JUNE 2016

5

Computer science Paper 2 (for more past questions visit http://gcerevision.com)

June 2016 Code: 0595 gcerevision.com

Instructions: answer any five questions (Two hours)

1. (a) Outline THRE advantages and THREE disadvantages of email communication compared to the

conventional postal system of sending textual information (6 marks)

(b) write the following file formats in full and state two characteristics of each

(i) GIF (3 marks)

(II) jpeg (3 marks)

(c) state the difference between the following pairs of terms. Give an example in each case

(i) system software and Application software (4 marks)

(ii) Primary storage and secondary storage (4 marks)

2. (a) (i) what is an operating system? (2 marks)

(ii) Give two examples of operating system. (2 marks)

(iii) outline FOUR functions of an operating system (4 marks)

(b) (i) what do you understand by the term computer generation? (2 marks)

(ii) Complete the table below on computer generations (2 marks)

Main Technology Generation

Integrated Circuit

Vacuum Tube

Very large-scale integration (VLSI)

Transistors

(c) Briefly explain the difference between an online system and a real-time system (4 marks)

(d) Give two difference between high level languages and low-level languages (4 marks)

3. (a) State the meaning of the following terms:

(i) Human-computer interface (2 marks)

(ii) Command line interface (2 marks)

(iii) Graphical user interface (2 marks)

(b) Below is an algorithm with each line of instruction numbered on the left:

1. Begin

2. Give the price of Item, A

3. Give the number of items bought, S

4. If S < 10 then

5. Total = A*S-100

6. Else

7. Total = A*S-300

8. Print Total

9. End

6



(i) state briefly what the algorithm does (3 marks)

(ii) state the two types of control structures uses in the algorithm (2 marks)

. (iii) Determine the output if the values of A = 300 and S = 3 (3 marks)

. (iv) Represent the algorithm above using a flow chart (6 marks)

4. (a) Briefly explain the difference between data validation and data verification (2 marks)

(b) A validation rule states that only alphabetic and/or numeric characters are acceptable and that an

entry must be least five characters in length. Which two of the following data would be REJECTED by the

system?

Good is123z giving w-6856 (2 marks)

Give reasons for your answer. (2 marks)

(c) The paragraph below contains five (5) abbreviations

“Most ISP in Cameroon provide internet connectivity to major banks. Internet connectivity requires

the TCP/IP protocol, while Web use requires the HTTP protocol. Interesting how some banks prefers DSL,

some go for ADSL and some others for broadband connections.”

(i) Write the 5 highlighted abbreviations in full (5 marks)

(ii) What are the roles of the TCP/IP and HTTP protocols? (2 marks)

(d) (i) sketch each of the following logic gates, clearly labelling inputs and outputs (3 marks)

OR AND NOT

(ii) Complete the following truth table

a b ā ā OR b

1 0

0 1

1 0

0 1

5. (a) briefly explain the following as used in computer networking

(i) Bandwidth (2 marks)

(ii) Optic fibre (2 marks)

(b) Briefly describe the following as used in information systems.

(i) Management Information System (2 marks)

(ii) Expert System (2 marks)

(c) A control system is designs to regulate the temperature of a piece of equipment by detecting the

color of a light bulb and sprinkling water for 20 seconds if the color is red. Study the flow charts given

below carefully and match letters in the flowchart symbols to the corresponding items in STATEMENT

LIST.

7



(you are not expected to draw the diagram)

(d) (i) What is a project? (2 marks)

(ii) Explain the roles of PERT and Gantt charts in project management (4 marks)

6. (a) With the aid of a suitable example in each case, state the meaning of

(i) Input device (2 marks)

(ii) Output device (2 marks)

(iii) Input/output device (2 marks)

(b) (i) write in full the acronyms RAM and ROM (2 marks)

(ii) Explain briefly the term ‘volatile’ in relation to RAM and ROM (2 marks)

(c) Explain the difference between a computer’s RAM and ROM in terms of:

(i) the role of the fata and instructions held in them (2 marks)

(ii) the ability to modify the data and instructions held in the (2 marks)

(d) (i) A common mistake is to assume that 1 kilobyte (KB) is equal to 1,000 bytes, instead of 1,024 bytes.

Explain why 1KB is equal to 1,024 bytes and not 1,000 bytes (2 marks)

(iii) Determine the storage capacity of a 4GB RAM in megabytes (MB) and Kilobytes (KB) (4 marks)

Start

A

B

D

C

NO

STATEMENT LIST

1. Is light red?

2. Check color of light

Bulb

3. Sprinkle water for 20

Seconds

4. Reset color of light

bulb and wait for 10

seconds

8



7. (a) Draw and label a simplified block diagram that shows the components of an information system

(6 marks)

(b) Explain the roles of the following components of a computer system

(i) CPU (2 marks)

(ii) primary memory (2 marks)

(iii) Secondary memory (2 marks)

(c) what does the processing speed of a microprocessor measure? (2 marks)

(d) Assume the Microprocessor A has a processing speed of 300 MHz and can execute 4 instructions in

each cycle. Microprocessor B has a processing speed of 250 MHz and can execute 5 instructions in each

cycle. Which of the two microprocessors will result in faster computations? State the reason. (6 marks)

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1.2. JUNE 2017

10



Instructions: answer any five questions (Two hours)

1. (a) briefly describe the following terms in relation to data security

(i) Data Encryption (2 marks)

(ii) Backup (2 marks)

(iii) Fire wall (2 marks)

(b) Briefly explain what is meant by data integrity (3 marks)

(c) state the difference between data verification and data validation (4 marks)

(d) (i) Briefly explain what you understand by computer simulation (2 marks)

(ii) state two advantages and two disadvantages of computer simulation (4 marks)

2. (a) Explain briefly the following data processing methods

(i) Batch processing (2 marks)

(ii) Online processing (2 marks)

(b) Describe the following types of human-computer interface

(i) Command line interface (3 marks)

(ii) Graphical User Interface (3 marks)

(iii) Menu-driven interface (3 marks)

(c) State the main role of each of the following network devices

(i) Bridge (1 mark)

(ii) Router (2 mark)

(iii) Modem (2 marks)

(d) Explain the difference between synchronous and asynchronous data transmission (2 marks)

3. (a) Draw a labelled diagram showing the basic components of a Central Processing Unit (4 marks)

(b) State three system buses that connect the components in (a) above (3 marks)

(c) Name four steps in the machine instruction cycle (4 marks)

(d) The following algorithm is intended to read three numbers and determine their product.Start

1. Set Count = 1

2. While Product = 1

3. While (Count <= 3) Do

4. Get a Number, N

5. Set Product = Product * N

6. Set Count = Count + 1

7. Print Product

8. Endwhile

END

11



Assume that the three numbers that are read in line 4 are 2,3 and 5

(i) Determine the output that is printed on line 7 each time the loop instructions are executed. (3 marks)

(ii) Draw a flow chart for the algorithm (6 marks)

4. (a) Given the logic circuit below:

(I) Write the logical expression for F and G (2 marks)

(II) Write TWO logic expression for H, first in terms of F and G, and then in terms of A, B, C and

D (3 marks)

(III) Given the following inputs to the logic circuit: A = TRUE, B = FALSE, C = FALSE, D = TRUE,

determine the values of F, G and H (3 marks)

(b) With aid of a suitable example in each case, state the meaning of:

(i) Input device (2 marks)

(ii) Output device (2 marks)

(iii) Input/output device (2 marks)

(c) Use binary arithmetic to evaluate

(i) 1100101 – 1010 (2 marks)

(ii) 1101011 + 1101 (2 marks)

(d) Convert the octal number 505 to a binary number (2 marks)

5. (a) Give simple definitions or explanations for the terms: - character, field, record, file, and database (5

marks)

(b) Assume you want to create a database of employees of a company, the departments they work for,

and their salaries. The tables below show sample data in the database.

A

B

D

C

H

G

F

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EMPLOYEE

ID FNAME LNAME DEPTCODE SALCODE

1 John Doe EN S1

3 Mary Hopkins MK S2

4 Peter Miles HR S2

6 Chris Jenkins EN S3

8 Susan Jenkins MK S1

DEPARTMENT

DEPTCODE DEPARTMENT

EN Engineering

MK Marketing

HR Human Relations

SALARY

SALCODE SALARY

S1 300000

S2 250000

S3 200000

S4 100000

(I) State the number of fields and records in the EMPLOYEE table (2 marks)

(II) What do you understand by the term key database? (2 marks)

(III) What is the most appropriate key for each of the three tables (3 marks)

(IV) With the keys chosen above, if the company has another employee whose FNAME, LNAME,

DEPTCODE and SALCODE are the same as for john Doe, how can the database management

system distinguish between these two employees? (2 marks)

(V) Would it be possible to add another employee called johnny Walker whose ID is 6? Explain

your answer. (2 marks)

(VI) Explain the problem that will arise if you try to add an employee whose SALCODE is S10,

without making any other change in the database. What change would you make so that

this employee’s data can be stored in the database? (4 marks)

6. John wants to set up a company to train people on Computer Literacy. Some of the people to train only

wants to know about using machines running the Microsoft Windows Operating System, while others

only want to know about using machines running the Linux operating system. John decides to set up two

personal computer laboratories: Lab A with Microsoft Windows and Lab B with Linux computers

Answer the following questions in relation to the scenario presented above.

(a) (i) What do you understand by the terms computer literacy? (2 marks)

(ii) State FOUR functions of an operating system. (4 marks)

(b) Answer the questions in this section to explain the types of training that john should provide

his trainees

(I) List five hardware components that the trainees need to know about so that they

can understand what happens from the time they type in a document to the time a

hardcopy is produced (2 marks)

(II) Name one hardware device, and the most relevant kind of application software that

can be used to improve the typing skills of the trainees (2 marks)

13



(III) State the category of network application software that must be installed on each

computer to enable easy access to the Web? Give two examples of his category of

software (4 marks)

(IV) List four important categories of application software that should include inn the

training. For each of them, state what it is used for. Your list should NOT include

your answer in (iii) above (6 marks)

7. (a) Implementation is one of the stages of SDLC, explain the following four conversation methods that

can be used during the implementation:

(i) Parallel conversion (2 marks)

(ii) Plunge conversion (2 marks)

(iii) Pilot conversion (2 marks)

(iv) Piecemeal conversion (2 marks)

(b) Explain the following in relation to programming languages

(i) Machine Language (3 marks)

(ii) Assembly language (3 marks)

(iii) High level language (3 marks)

(c) State two disadvantages and one advantage of a machine language (3 marks)

14

1.3. JUNE 2018

15

www.thebigbrains.org16




2. ANSWER SECTION

20

2.1. JUNE 2016

21

II. Answers to Cameroon GCE O/L Computer Science Paper 2, June 2016

Disclaimer:

This his not an offichial markhing guhide. Te answers ghiven here express a personal pohint of vhiew. Pleaseuse whith ficauthion. Feel free to ficontrhibute or report a problem at gamonana.wordpress.ficom/ficontafict

1.

(a) 03 advantages of emahil ficommunhificathion: hit his fast;hit his hinexpenshive; hit his permanent - you ficankeep a reficord of messages and replhies, hinficludhing detahils of when a message was reficehived

03 dhisadvantages of emahil ficommunhificathion: aficficesshible to others that fican read your emahilswhithout you knowhing; presenfice of spam that fican food your mahil box whith undeshirablemahil ; presenfice of vhirus that fican damage your ficomputer.

(b)

hi. GIF: Graphhific Interfichange Format

characteristics: ghif uses loss-less ficompresshion algorhithm meanhing hit does not getblurry; ghif fican be anhimated; hit dhisplays a maxhimum of 256 ficolours. This makes hit a poorformat for photographhific himages

ii. JPEG: Johint Photographhific Experts Group

characteristics: jpeg uses a lossy ficompresshion algorhithm; hit his ficapable of dhisplayhing amhillhion of ficolors that makes hit suhitable for photographhific himages; hit ficannot be anhimated

(fic)

hi. System sofware his sofware used to operate ficomputer hardware. It provhides platformto run applhificathion sofware. E.g Operathing System. Application sofware his sofwarethat provhides fafichilhithies to user to perform spefichiffic task. E.g word proficessor sofware

hihi. Primary storage otherwhise ficalled mahin memory his memory that fican be dhirefictlyaficficesed by CPU. Prhimary storage his volathile hin nature. Examples hinficlude RAM, Cafiche

Secondary storage ficannot be dhirefictly aficficessed by the CPU. It his used to store data on along term bashis . Examples hinficlude Hard Dhisk drhives, USB drhives

2.

(a)

hi. An operating system (OS) his system sofware that manages hardware and sofwareresourfices of a ficomputer.

hihi. Ubuntu, CentOS, Whindows 7

22

hihihi. Memory Management, Fhile management, Boothing of the ficomputer,Proficess Management, Provhidhing Interfafice (Command Lhine Interfafice and GraphhificalUser Interfafice)

(b)

hi. A Computer generation his ficharaficterhized by a major tefichnologhifical development thatfundamentally fichanges the way a ficomputer operates, lhike the use of vaficuum tubes,transhistors, and the mhificroproficessor.

hihi.

Main Technology Generation

Integrated Chirficuhit 4th

Vaficuum Tube 1st

Very large-sficale Integrathion (VLSI) 3rd

Transhistors 2nd

(fic) A real time system his a system whhifich provhides himmedhiate proficesshing and response to thedata behing hinputed e.g an Ahirlhine Reservathion system

An online system his a system ficonneficted to the Internet. Sufich system may nothimmedhiately proficess and ghive a response to an hinputed data. E,g browshing a webpage

(d) hhigh level langage his mafichhine hindependent whhile low level langage his mafichhine dependent

hhigh level langage his ficlose to human langage whhile low level his not ficlose to humanlanguage

3.

(a)

hi. Human–computer Interface (HCI) his a feld of study that foficuses on the deshign anduse of ficomputer tefichnology, and hin parthificular the hinteraficthion between humans (users)and ficomputers

hihi. A command-line interface his a text based way of hinteraficthing whith a ficomputer wherethe user hissues ficommands hin the form of suficficesshive lhines of text ficalled ficommand lhinesand reficehives responses also hin the form of suficficesshive lhines of text.

23

hihihi. A GUI his a vhisual way of hinteraficthing whith a ficomputer program ushing hitems sufich asWhindows, Ificons, Menus and Pohinters (WIMP)

Illustration 7: An example of GUI

24

(b)

hi. the algorhithm multhiplhies the prhifice of an hitem whith the number of hitems

hif the number of hitems his less than 10, a dhisficount of 100 his applhied to the total prhifice

hif the number of hitems his greater than or equal to 10, a dhisficount of 300 his applhied to thetotal prhifice

hihi. Sequenthial and Seleficthion Control Strufictures

hihihi. Total = 800

hiv.

25

Te hinput/output symbol his .

but beficause my sofware does not have hit I have used

4.

(a) Data Validation his about fichefickhing hif the hinput data ficonforms whith the data requhirements of the system to avohid unwanted data. An example his a date fichefick to avohid hinputhing dates that are beyond the ficurrent date.

Data Verifcation his a way of ensurhing the user types hin what he or she hintends .hi.e makhing sure the user does not make a mhistake when hinputhing data. An example of thhis hinficludes double entry of data when ficreathing a password to prevent hinficorrefict data hinput

(b) Good:his less than 5 ficharaficters hin length

w-6856: has a non alphabethific or numerhific ficharaficter whhifich his -

(fic)

hi. TCP/IP: Transmhisshion Control Protoficol/ Internet Protoficol

HTTP: HyperText Transfer Protoficol

DSL: Dhighital Subsficrhiber Lhine

ADSL: Asymmetrhific Dhighital Subsficrhiber Lhine

hihi. HTTP his used to transmhit webshite hinformathion (text,graphhific, sound, audhio…) aficross the Internet

TCP/IP transmhisshion of data (web pages, emahil, fles …) aficross the Internet

26

(d)

hi. EXPLANATION: fichoose the OR, AND and NOT gates

hihi.

A B Not A (NOT A) or B

1 0 0 0

0 1 1 1

1 0 0 0

0 1 1 1

5.

(a)

hi. Bandwidth: the amount of data that fican be transmhited hin a fxed amount of thime. It hisexpressed as bytes per seficond

hihi. Optic fibre: A tefichnology that uses glass threads (fbers) to transmhit data

(b)

hi. Management Information System: refers to an hinformathion system that his used hindefichishion-makhing and provhide tools for managers to ficoordhinate, evaluate and effichientlymanage an organhizathion

27

hihi. an expert system his a ficomputer system that emulates the defichishion-makhing abhilhity of a human expert

(fic) A:2

B: 1

C:3

D:4

(d)

hi. a project his an temporary endeavour whith a defned start and end date.

hihi. Tese two projefict management tools help:

to hidenthify tasks

to esthimate projefict durathion

to show the hinterdependenficy of tasks

PERT (Program Evaluation Review Technique) charts are generally used before aprojefict beghins to plan and determhine the durathion of eafich task. Tey are used for largeand ficomplex projeficts. Gantt charts are used whhile a projefict his happenhing to breakprojeficts hinto smaller tasks and hhighlhight sfichedulhing ficonstrahints. Tey are used forsmall projeficts.

6.

(a)

hi. An input device his a hardware devhifice that sends data to a ficomputer allowhing you tohinterafict whith hit. Examples hinficlude : keyboard, mouse, sficanner, mhificrophone, bar ficodereader.

hihi. An output device his a hardware devhifice that dhisplays (or reficehives) data from aficomputer. Examples hinficlude: Prhinters, Monhitors, Projefictors

hihihi. An input / output device his a devhifice that fican both send data to a ficomputer and dhisplay(or reficehive) data from a ficomputer. Example: A USB Drhive sends data to a ficomputerand dhisplays (or reficehives) data from a ficomputer

(b)

hi. RAM: Random Aficficess Memory

ROM: Read Only Memory

28

hihi. RAM his volathile, whhile ROM his not

(fic)

hi. Te data stored hin ROM his used prhimarhily hin the startup proficess of a ficomputer, whereas data hin RAM his used afer the Operathing System has been loaded

hihi. RAM data fican be modhify, ROM data his not modhifable

(d)

hi. 1KB = 1,024 bytes beficause 1KB his 2 10 bytes

hihi. 4GB = 4000MB = 400000000KB

7.

(a) EXPLANATION: there are 5 ficomponents of an Informathion System: People (Proficedures),Hardware, Sofware, Data, Network

(b)

hi. CPU: hit his used to proficess data

hihi. Primary Memory: thhis his mahin memory. It stores data dhirefictly aficficesshible by the CPU.Eg. RAM

Illustration 8: Components of an Information System

29

hihihi. Secondary Memory: thhis his memory that holds data on a long term bashis. It stores datathat his not dhirefictly aficficesshible by the CPU e.g Hard dhisk drhive

(fic) hit measures the performanfice of a CPU. Te unhit of measurement his ficalled Hertz

(d) thime = Number of hinstruficthions / frequenficy

for mhificroproficessor A, thime = 4/300 = 0.01s

for mhificroproficessor B, thime = 5/250 = 0.02s

mhificroproficessor A his faster shinfice hit exeficutes hits hinstruficthion hin fewer thime

EXPLANATION: truly speakhing time = Numiber of instructions * (1 / frequency)

30

2.2. JUNE 2017

31

I. Answers to Cameroon GCE O/L Computer Science Paper 2, June 2017

Disclaimer:

This his not an offichial markhing guhide. Te answers ghiven here express a personal pohint of vhiew. Pleaseuse whith ficauthion. Feel free to ficontrhibute or report a problem at gamonana.wordpress.ficom/ficontafict.

1.

(a)

hi. Data Encryption : This his a seficurhity method by whhifich data his ficonverted to a formwhere you need a seficret key to aficficess or read hit. This seficret key his formally ficalledEnficrypthion key. Te ficonverted text his ficalled fichiphertext whhile the orhighinal text hisplahintext

hihi. Backup : thhis refers to makhing ficophies of data to use hin the event the orhighinal data his lost

hihihi. Firewall : thhis his a seficurhity system that flters hinficomhing and outgohing traffic(messages)based on defned sets of rules. It his shimhilar to a physhifical barrhier that flters aficficess hin andout of the ficompound.

(b) Data integrity his the aficficuraficy and ficompleteness (ficonshistenficy) of data throughout hitslhifeficyficle. Data hintegrhity fican be mahintahined through the use of varhious error-fichefickhingmethods and valhidathion proficedures.

(fic) Data Verifcation his a way of ensurhing the user types hin what he or she hintends .hi.e makhingsure the user does not make a mhistake when hinputhing data. An example of thhis hinficludesdouble entry of data when ficreathing a password to prevent hinficorrefict data hinput

Data Validation on the other hand his about fichefickhing hif the hinput data ficonforms whith thedata requhirements of the system to avohid unwanted data. An example his a date fichefick toavohid hinputhing dates that are beyond the ficurrent date.

(d)

hi. Computer Simulation: thhis refers to the use of a ficomputer to himhitate a system usuallya real-world system. Te himhitathion proficess his based on a sets of mathemathificalequathions (mathemathifical model). Te purpose of shimulathion his to predhifict the results ofsomethhing

hihi. Advantages:

32

Avoid disturbing real world systems: Whith Computer Shimulathion, hit his posshible to test the behavhior ofsomethhing. We fican model a system ficlose enough to real world. Experhiments are done on the model whithout dhisturbhing the real world system.

Help Students: Teafichers fican do shimulathion of systems and explahin to students. Students fican get an hidea of any system eashily be seehing a shimulathion

Dhisadvantages:

Expensive : Computer shimulathion his expenshive beficause hit requhires a group of hhighly qualhifed hindhivhiduals buhild the shimulathion model

Computer limitation : Complex shimulathion hinvolves a ficomputer whith hhigher memory and proficessor speed. This his another drawbafick of shimulathion.

2.

(a)

hi. Batfich proficesshing his a method of runnhing data jobs periodically whith little or no user interaction. Batfich jobs are ficolleficted hin bulk rather than dhirefict hinput from user and are proficessed at a later thime. Example :Sfichedulhing the automathific payment of employees every month

hihi. Onlhine proficesshing his a method of runnhing data jobs continuously as they are hinputed.Te hinputed data his dhirefictly proficessed and outputed. Example: the bank ATM his anexample of onlhine proficesshing as data his himmedhiately proficessed and outputed asficustomers send hinput to the mafichhine.

Illustration 1: A bank ATM

33

(b)

hi. A command-line interface his a text based way of hinteraficthing whith a ficomputer wherethe user hissues ficommands hin the form of suficficesshive lhines of text ficalled ficommand lhinesand reficehives responses also hin the form of suficficesshive lhines of text. This type of hinterfaficehis not hideal for novhifice users as you must remember the range of dhiferent ficommands

hihi. A GUI his a vhisual way of hinteraficthing whith a ficomputer program ushing hitems sufich asWhindows, Ificons, Menus and Pohinters (WIMP)

Illustration 2: A command line interface

34

hihihi. Menu Driven Interface : thhis his an hinterfafice that ficonshist of a serhies of menus and sub-menus whhifich the user aficficesses by presshing butons, ofen on a toufich-sficreen devhifice. Aficommon example his the ATM

Illustration 3: A GUI

35

(fic)

hi. Bridges are shimhilar to repeaters and hubs hin that they broadficast data to every node

hihi. A router his a devhifice that forwards data pafickets along networks. Routers are loficated atgateways, the plafices where two or more networks ficonnefict.

hihihi. Modem: Short for modulator/demodulator, a modem his a hardware devhifice that allows aficomputer to send and reficehive hinformathion over telephone lhines. It his otherwhise ficalleddhialup modem whhifich his dhiferent from broadband modem

EXPLANATION: Computer hinformathion his stored dhighitally, whereas hinformathiontransmhited over telephone lhines his transmhited hin the form of analog waves. Whensendhing a shignal, the devhifice ficonverts ("modulates") dhighital data to an analog audhioshignal, and transmhits hit over a telephone lhine. Shimhilarly, when an analog shignal hisreficehived, the modem ficonverts hit bafick ("demodulates" hit) to a dhighital shignal.

Illustration 4: Example of Menu driven Interface

36

(d) Synchronous data transmission his a data transfer method hin whhifich data bloficks areficonthinuously and ficonshistently behing transfer. Examples hinficlude : telephonhific ficonversathions,vhideo ficonferenfiching

Asynchronous data transmission his a data transfer method hin whhifich data his transmhiteddhisficonthinuously and a start and stop behing must behing hinsereted hin eafich data blofick tohinform the reficehiver where hit beghins and ends. Examples hinficlude : emahils

3.

(a) EXPLANATION: C.P.U :- Te CPU his the heart and brahin of a ficomputer .Te threecomponents of the CPU:

▪ (A.L.U) Arhithmethific loghific unhit .

▪ (C.U) Control Unhit .

▪ (M.U) Memory Unhit .

A.L.U :- An arhithmethific loghific unhit his a dhighital fichirficuhit used hin ficomputers to performarhithmethific and loghific operathion .

C.U :- A ficontrol unhit his fichirficuhitry that dhireficts operathions whithhin a ficomputer’s proficessor.

M.U :- Memory unhit his the amount of data that fican be stored.

(b) Address Bus: It his a group of whires whhifich ficarrhies address only.Address bus hisunhidhireficthional beficause data fow hin one dhireficthion, from mhificroproficessor to memory or frommhificroproficessor to Input/output devhifices

Illustration 5: Basic Components of a CPU

37

Data Bus:It his a group of whires whhifich ficarrhies Data only.Data bus his bhidhireficthional beficausedata fow hin both dhireficthions, from mhificroproficessor to memory or Input/Output devhifices andfrom memory or Input/Output devhifices to mhificroproficessor

Control Bus: It his a group of whires, whhifich his used to generate thimhing and ficontrol shignals

(fic) the mafichhine hinstrficuthion ficyficle ficonshists of : Fetfich the hinstruficthion, deficode the hinstruficthion,Exeficute and Store result.

(d)

hi. for N = 2, Produfict = 2

for N = 3, Produfict = 6

for N = 5, Produfict = 30

hihi.

Illustration 6: Types of buses in a Computer

38

39

EXPLANATION: Te defichishion symbol always appear at the end of a whhile loop. If theficondhithion his true, the arrows goes bafick to the start of the loop otherwhise the loop histermhinated

the hinput/output symbol his .

but beficause my sofware does not have hit I have used

4.

(a)

hi. F represents the result of an AND GATE: A.B

G represents the result of an OR GATE: C+D

hihi. H: F + G

H:(A.B) + (C+D)

hihihi. F: FALSE

G: TRUE

H: TRUE

(b)

hi. An input device his a hardware devhifice that sends data to a ficomputer allowhing you tohinterafict whith hit. Examples hinficlude : keyboard, mouse, sficanner, mhificrophone, bar ficodereader.

hihi. An output device his a hardware devhifice that dhisplays (or reficehives) data from aficomputer. Examples hinficlude: Prhinters, Monhitors, Projefictors

hihihi. An input / output device his a devhifice that fican both send data to a ficomputer and dhisplay(or reficehive) data from a ficomputer. Example: A USB Drhive sends data to a ficomputerand dhisplays (or reficehives) data from a ficomputer

(fic)

hi. 111001101 (represents 101 hin base ten) - 010011010 (represents 10 hin base ten) = 110111011(represents 91 hin base ten)

40

EXPLANATION: whith bhinary subtraficthion 0 – 1 = 1 and 1 his borrowed from the nextshignhifficant bhit. Note that whith suficficesshive borrows, the values are deduficted aficficordhingly.

Eg 1: ficonshider 1001 – 101 . hin the thhird substraficthion (I.e 0 – 1) 1 his borrowed andappended to zero whhifich now beficomes 10 – 1 (I.e 2 -1) whhifich his equal to 1. Te fourthsubstraficthion beficomes 0 – 0 = 0. the fnal result ghives 100.

Eg 2: Conshider 1000 – 111 = 0001. In the frst substraficthion (I.e 0 - 1) 1 his borrowed fromthe 1 at the fourth poshithion. This 1 his appended to the zero at the thhird poshithionbeficomhing 10. 1 agahin his deduficted here so that what his lef his 1 and the seficond poshithionbeficomes 10. 1 his agahin deduficted here so that what his lef his 1 and we have a 10 at thefrst poshithion. We now have 10 – 1 whhifich ghives 1. Te next substraficthions are 111 – 111whhifich ghives 000. henfice the result 0001. Vhishit thhis to learn more about Bhinarysubtraficthion and here to have for bhinary to defichimal ficonvershions

hihi. 111011011 (represents 107) + 001011 01 (represents 13) = 111111000 represents 120 notethat whith bhinary addhithion 1 + 1 = 0 and 1 his ficarrhied. Also 1+1+1=1 and 1 his ficarrhied

(d) 5058 = 110101001 011 2 . EXPLANATION: ofictal means base 8 notathion. Tere are only 8symbols : from 0 to 7. the algorhithm to ficonvert from ofictal to bhinary his :

▪ ficonvert eafich dhighit hin the ofictal number hinto hits 3 dhighit bhinary equhivalent.

▪ Te result his the bhinary number

5.

(a) Character : hit ficonshist of 8 bhits. 8 bhits fican also be ficalled a byte. A bhit his the smallest unhit ofdata representathion. Te value of a bhit his ehither 0 or 1.

Field : a feld ficonshist of a group of ficharaficters. A feld his used to desficrhie an enthity (objefict,person, plafice or event). E.g the enthity person may have as feld: name

Record : a Reficord his a ficolleficthion of felds, whith eafich feld desficrhibhing the enthity. E.g theenthity person may have a reficord ficonshisthing of the felds : name, age and sex

File: A group of related reficords make up a fle. E.g the Person’s fle ficonshisthing of a serhies ofreficords of persons

Database : hit refers to an hintegrated ficolleficthion of related reficords or fles. Databases aremanaged by spefichialhised sofware ficalled Database Management Systems (DBMS)

EXPLANATION: Tese hitems from the Hierachy of data.

(b)

hi. 5 felds and 5 reficords

41

https://www.math-only-math.com/binary-subtraction.html

https://www.rapidtables.com/convert/number/binary-to-decimal.html

hihi. key: hit his the feld that enables to unhiquely hidenthify a reficord

hihihi. EMPLOYEE → ID; DEPARTMENT → DEPTCODE; SALARY → SALCODE

hiv. by ushing the ID feld whhifich whill be dhiferent for both employees

v. NO. Beficause the entry hin the ID feld shoud be unhique. Te ID 6 has already behing used

vhi. some of the employee’s ficorrespondhing reficord mhight not fgure hin the DEPARTMENTand SALARY tables. Add the ficorrespondhing reficord to the DEPARTMENT andSALARY tables

6.

(a)

hi. Computer literacy his defned as the knowledge and abhilhity to uthilhize ficomputers andrelated tefichnology effichiently

hihi. Boothing, Memory management, Dhisk management, Provhidhing Interfafice.

(b)

hi. keyboard, mouse, monhitor, prhinter

hihi. Hardware devhifice: keyboard

sofware: A Word Proficesshing sofware

hihihi. Internet browser: Mozhilla Fhirefox, Google Chrome

hiv. Spreadsheet Sofware : A tool used to ficreate leters, word sheets

Desktop Publhishhing Sofware: A tool used to ficreate hillustrathive worksheets, banners

Database Sofware: A tool used to store data lhike text hinformathion

Presentathion Sofware: used to ficreate multhimedhia apps

7.

(a)

EXPLANATION: SDLC stands for Sofware Development Lhife Cyficle. It represents allthe phases hinvolved hin the development of a sofware.

hi. Parallel conversion his an himplementathion tefichnhique hin whhifich an exhisthing system runshin parallel whith the new system, to verhify that both produfice hidenthifical results and thusensure that the new system fican ficorrefictly takeover the exhisthing system.

42

hihi. Plunge conversion his an himplementathion tefichnhique hin whhifich there his an abrupt fichangefrom the old system to the new system at a predefned thime. This method forfices theusers to make the new system work shinfice they have no other method to fall bafick on.

hihihi. Pilot conversion his an himplementathion tefichnhique hin whhifich a workhing vershion of thesystem his himplemented hin one part of the organhizathion, sufich as a shingle department. Asthe system his behing used, fichanges fican be made to himproved hit. When the system hisdeemed ficomplete, hit his hinstalled throughout the organhizathion, ehither at onfice (dhirefictficonvershion) or gradually (phased or phiefice meal ficonvershion). Philot ficonvershions are onlyposshible hin organhizathions that have dhisficrete seficthions or branfiches.

hiv. Piecemeal conversion otherwhise ficalled Phased ficonvershion his an himplementathiontefichnhique hin whhifich the new system his hintroduficed gradually. It fican be used when hit hisnot posshible to hinstall a new system throughout an organhisathion all at onfice.

(b)

hi. Machine Language his a programmhing language ficonshisthing of bhinary or hexadefichimalhinstruficthions whhifich a proficessor fican respond to dhirefictly. Sufich programmhing langagesneed no translathions to be understood by the proficessor. Mafichhine languages areproficessor dependent and thus not portable (hie the ficode wrhiten for one proficessor ficannot be used on a dhiferent proficessor). Mafichhine langages are dhifficult to read, wrhite andmahintahin

hihi. An assembly language, also refered to as ASM, his a low-level programmhing languagehin whhifich there his a very strong ficorrespondenfice between the program's statements andthe hinstruficthions whhifich the proficessor understands. Assembly langages are translatedhinto mafichhine langage ushing an assembler Assembly langages are also dhifficult toread,wrhite and mahintahin. Tey are not very portable.

hihihi. High level language his a programmhing langage ficlose to human langage, his mafichhinehindependent and thus portable. Tey are eashier to read, wrhite and mahintahin. Tey aretranslated hinto mafichhine langage ushing a ficomphiler or hinterpreter

(fic) two dhisadvantages of Mafichhine Language: dhifficult to read, wrhite; not portable

advantage: quhifickly hinterpreted by the Proficessor

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2.3. JUNE 2018

44

III. Answers to Cameroon GCE O/L Computer Science Paper 2, June 2018

1.

(a)

i. SDLC: Software Development Life Cycle

ii. BIOS: Basic Input Output Software

iii. PDF: Portable Document Format

iv. CPU: Central Processing Unit

(b)

i. Arithmetic logic unit (ALU), Control Unit (CU) and Memory Unit (MU) .

ii. A.L.U :- it is used in computers to perform arithmetic and logic operations .

C.U :- A control unit is a set of circuits that directs operations twithin a computer’s processor.

M.U :- is the amount of data that can be stored.

iii. Te fetch Decode Execute Cycle is also knotwn as the Instruction Cycle.

Fetch: Te Program Counter (PC) points to the address of the next instruction. Tis instruction is fetched and stored inside the Instruction Register (IR)

Decode: Decode the Encoded Instruction found in the IR

Execute: Perform the Decoded Operation e.g For an addition Operation, take the values of ttwo registers and actually add them Te result generated by the operation is stored in the main memory or sent to an output device.

Te processor goes back to the program counter to fnd the next instruction and a netwcycle begins

45

2.

(a)

i. Network Interface Card: A Nettwork interface card is a hardtware component ( circuit board) that connects a computer to a computer nettwork, usually a LAN (Local Area Nettwork)

ii. Modem: Short for modulator/demodulator, a modem is a hardtware device that allotws acomputer to send and receive information over telephone lines. It is othertwise called dialup modem twhich is diferent from broadband modem

EXPLANATION: Computer information is stored digitally, twhereas information transmited over telephone lines is transmited in the form of analog twaves. When sending a signal, the device converts ("modulates") digital data to an analog audio

Illustration 9: A Network Interface Card

Illustration 10: Examples of Modems

46

signal, and transmits it over a telephone line. Similarly, twhen an analog signal is received, the modem converts it back ("demodulates" it) to a digital signal

iii. Router: A router is a device that fortwards data packets along nettworks. Routers are located at gatetways, the places twhere ttwo or more nettworks connect.

(b)

i. A: IF symbol

B:Input / Output Symbol

C: Start/Stop Symbol

ii. Pseudocode is a textual representation of an algorithm; for example in English, twhile fotwchart is a graphical representation of

(c)

i. Finiteness: An algorithm should terminate afer a fnite number of steps

Precision (Defniteness): Each step of an algorithm must be clear and not ambiguous.

Input & Output: the algorithm must accept zero or more input and must produce at least one output.

ii. You have passed. Keep it up.

iii. Sequential construct: Lines 1,2,3 and 4

Illustration 11: An example of Router

47

Selection construct: Line 5

3.

(a)

i. difcult to search for information;

possibility of duplicates.

Poor data security.

ii. A Database Management System (DBMS) is a software used to manage data. A DBMS allotw users to create, read, update and delete data.

iii. A database refers to an integrated collection of related records. Databases are managedby specialised software called Database Management Systems (DBMS)

iv. A key is a feld (or set of felds) that helps to uniquely identify a record.

v. Data integrity is the accuracy and completeness (consistency) of data throughout its lifecycle.

(b) User interface: Tis is the means by twhich the user and a computer system interact to complete tasks

(c)

i. Graphical User Interface: visual tway of interacting twith a computer

ii. Voice Interface: speech based tway of interacting twith a computer

iii. Command Line Interface: Text based tway of interacting twith a computer

4.

(a)

i. Storage Capacity in Bytes = 2 * 100 * 10 * 512 = 100240000 Bytes

ii. 100240000Bytes = 1024KBytes

EXPLANATION: A hard disk drive consist of a set of platers. Each plater is made up of concentric circles called Tracks. A sector is a portion of a track. It is the smallest unit of storage.

48

(b)

i. faster speed and less fle loading time

ii. avoid the loss of data by keeping data in a secondary (another) location

iii. prevent the atack of virus, protect your computer.

49

(c)

i. Read Only Memory:this is a storage location that keeps unmodifable data.

ii. Random Access Memory: this is main memory that stores modifable data

iii. Hard disk: this is computer memory that stores data on a long term basis.

(d)

i. Cybercrime: is a crime that involves a computer and a nettwork

ii. Spamming : fooding of someone’s e-mail twith untwanted emails

Phishing: fraudulent atempt to obtain someone’s personal information

5.

(a)

i. Confdentiality: ensures that sensitive information are accessed only by an authorized person

ii. Software damage: anything that can cause harm to software.

iii. Unauthorized access: Tis is twhen someone gains access to a system using someone else's account or other methods. For example, if someone kept guessing a passtword or username for an account that twas not theirs until they gained access, it is considered unauthorized access.

iv. Unauthorized Use: this is the use of a system twithout the otwner’s consent

(b) Measures to check Confdentiality: Use of username/passtword; data encryption

Measures to check Unauthorized access: install fretwall, install antivirus (or spytware)

(c)

i. EXPLANATION:

• A hexadecimal number is a base-16 number and uses sixteen distinct symbols : from 0 to 15.

An octal number or oct for short is a base-8 number and uses the digits 0 to 7. Octal numerals can be made from binary numerals by grouping consecutive binary digits into groups of three (starting from the right).

• Hotw to convert?

• Step 1: Find the equivalent binary number for each digit in the given hexadecimal number.

Add 0’s to the lef if any of the binary equivalent is shorter than 4 bits

50

• Step 2: Separate the binary digits into groups, each containing 3 bits or digits from right to

lef. Add 0s to the lef, if the last group contains less than 3 bits.

• Step 3: Find the octal equivalent for each binary group.

• Note that for a hexadecimal number A is equivalent to 10, B to 11, C to 12, … E to 15

Source:

SOLUTION

• to convert DC to octal, twe twill apply our three step method above

◦ step 1: DC16 → 1101 110002

◦ step 2: 1101 110002 → 0110011 1002. (the last zero has been added to have groups of 3 digits

each

◦ Step 3: 3348

ii. 10001110012 = (1*27) +(0*26) +(0*25) +(1*24) +(1*23) +(1*22) +(0*21) +(1*20)

= 128 + 0 + 0 + 16 + 8 + 4 + 0 + 1

= 150710

Check the correctness of this anstwer here

6.

(a)

i. Analysis → Design → Implementation → User Support

ii. Analysis: Data Collection, Data Interpretation, twrite the software requirements

Design: Implementation of process (activity) diagrams (using fotwchart), dratwing ofscreen layouts

(b)

i. Systems Analyst: they do Data Collection and analysis. Tey are also involved indesigning the system. Tey produce the System’s Requirement.

ii. Programmer: they implement the system. Tey twrite software code

(c)

i. twtwtw: World Wide Web

51

https://www.rapidtables.com/convert/number/binary-to-decimal.html

ii. Te Internet is a global nettwork of connected computers twhile twtwtw is a collection oftweb pages accessed through the Internet. Te Internet can be vietwed as a road andtwtwtw as a car using that road.

iii. A blog is a twebsite , typically one run by an individual or small group, that is twritenin an informal or conversational style. An Internet Relay Chat (IRC) is a system forchating that involves a set of commands and a client/server software. Some of thecommands include: “/help” twhich is used to bring up a list of all the commands or thehelp twindotw.

(d)

i. A social nettwork is a twebsite or virtual community that allotws people twith similarinterests to come together, share and comment on information, photos and videos.

ii. Facebook, LinkedIn, Ttwiter

iii. advantage:

It allotws for Information Sharing.

Stay in touch twith friends and family that are distant apart.

Disadvantage:

presence of Fake information.

Addiction, Reduced Privacy

7.

(a)

i. An operating system (OS) is system software that manages hardtware and software resources of a computer. Examples include: Windotws, Linux, MacOS

ii. Memory Management,

File management,

Booting of the computer,

Process Management,

Providing Interface (Command Line Interface and Graphical User Interface).EXPLANATION: A comprehensive list of the functions of the Operating System canbe found here. Look at the section “Characteristics of Operating System”

(b)

52

https://www.tutorialspoint.com/computer_fundamentals/computer_operating_system

i. high level langage is machine independent twhile lotw level langage is machinedependent;

high level langage is close to human langage twhile lotw level is not close to humanlanguage.

ii. Lotw level language: x86 assembly

High Level Language: python

(c)

i. An Interpreter translates a program one statement at a time to produce machine code.It does not generate an intermediate object code. Programming languages like Python,PHP, use Interpreters

ii. A compiler translates a program as a twhole into machine code. It generates anintermediate object code before producing the machine code. Programming languageslike C, C++, Java use compilers

(d)

i. P = X + Y

ii. Q = Z + W

iii. R = P + Q

53

SOME TIPS WHEN WRITING THE EXAM 1. To get familiar with the type of questions asked, get to solve as many past questions

as possible;

2. You must not necessarily solve all GCE past questions for you to succeed. A couple of

past questions for 3 to 5 years is enough;

3. Start with the easy questions first, it gives you motivation. Once you are done with

the easy questions you can go tackle the difficult one.

4. When revising for your exam, do not seek to cram but to understand your notes.

Understand in your words would stick better into your brain than trying to memorize

the notes of your teacher, word for word;

5. Pray before you start writing your exam. God always guide his Children.

GAMO NANA,

Tel: 697518768.

Email: [email protected]

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Documents

CAMEROON PAST GCE ORDINARY LEVEL COMPUTER SCIENCE … · 2018. 5. 8. · Computer Science at the Ordinary level consist of 3 papers namely: Paper 1, 2 and 3. Paper 2 accounts for