WAEC SSCE - Computer Studies - 2016 (Essay)
Frage 1 Bericht
(a) (i) Define computer virus.
(i) List three types of computer network security breach.
(b) State five sources of computer network security breach.
(a)(i) Definition of computer virus
A computer virus is a malicious program written to attach itself to other programs or files and to replicate itself, so that it can spread from one computer to another and damage, corrupt or interfere with the normal working of the system.
(a)(ii) Three types of computer network security breach
- Hacking / unauthorised access to the network.
- Virus, worm or malware infection.
- Denial of Service (DoS) attack that floods the network so genuine users are shut out. (Other acceptable answers: phishing, eavesdropping/interception, spoofing.)
(b) Five sources of computer network security breach
- Infected external storage media such as flash drives and memory cards.
- Downloads and e-mail attachments from untrusted Internet sites.
- Hackers and intruders attacking the network from outside.
- Dishonest or careless insiders (staff or users who misuse access rights or leak passwords).
- Weak or missing security measures such as poor passwords, unpatched software and lack of a firewall or anti-virus.
Antwortdetails
(a)(i) Definition of computer virus
A computer virus is a malicious program written to attach itself to other programs or files and to replicate itself, so that it can spread from one computer to another and damage, corrupt or interfere with the normal working of the system.
(a)(ii) Three types of computer network security breach
- Hacking / unauthorised access to the network.
- Virus, worm or malware infection.
- Denial of Service (DoS) attack that floods the network so genuine users are shut out. (Other acceptable answers: phishing, eavesdropping/interception, spoofing.)
(b) Five sources of computer network security breach
- Infected external storage media such as flash drives and memory cards.
- Downloads and e-mail attachments from untrusted Internet sites.
- Hackers and intruders attacking the network from outside.
- Dishonest or careless insiders (staff or users who misuse access rights or leak passwords).
- Weak or missing security measures such as poor passwords, unpatched software and lack of a firewall or anti-virus.
Frage 2 Bericht
(a) An electronic book is made up of 500 pages and there are 16 lines of 24,000 bits line on each page.
Complete the space it will occupy on a computer in megabytes.
(b) Give an example of auxiliary storage.
(c) In the table below:
(i) List the two main types of computer software.
(ii) Give two examples under each in 4(c)i)
| main type | example |
| i | A |
| B | |
| ii | A B |
(a) Space occupied by the electronic book.
Given: 500 pages; 16 lines per page; 24,000 bits per line.
Step 1 - total number of bits:
\[ \text{Total bits} = 500 \times 16 \times 24000 = 192{,}000{,}000 \text{ bits} \]
Step 2 - convert bits to bytes (8 bits = 1 byte):
\[ \text{Bytes} = \dfrac{192{,}000{,}000}{8} = 24{,}000{,}000 \text{ bytes} \]
Step 3 - convert bytes to megabytes:
Using \(1\,\text{MB} = 1{,}000{,}000\) bytes:
\[ \dfrac{24{,}000{,}000}{1{,}000{,}000} = 24 \text{ MB} \]
The book therefore occupies about 24 MB. (If the binary convention \(1\,\text{MB} = 1{,}048{,}576\) bytes is used instead, the answer is \(24{,}000{,}000 \div 1{,}048{,}576 \approx 22.89\,\text{MB}\).)
(b) An example of auxiliary (secondary) storage: hard disk drive (also acceptable: flash/USB drive, CD-ROM, DVD, or magnetic tape).
(c) The two main types of computer software with examples:
| Main type | Examples |
|---|---|
| (i) System software | A - Operating system (e.g. Windows) B - Utility program / device driver |
| (ii) Application software | A - Word processor (e.g. Microsoft Word) B - Spreadsheet (e.g. Microsoft Excel) |
Antwortdetails
(a) Space occupied by the electronic book.
Given: 500 pages; 16 lines per page; 24,000 bits per line.
Step 1 - total number of bits:
\[ \text{Total bits} = 500 \times 16 \times 24000 = 192{,}000{,}000 \text{ bits} \]
Step 2 - convert bits to bytes (8 bits = 1 byte):
\[ \text{Bytes} = \dfrac{192{,}000{,}000}{8} = 24{,}000{,}000 \text{ bytes} \]
Step 3 - convert bytes to megabytes:
Using \(1\,\text{MB} = 1{,}000{,}000\) bytes:
\[ \dfrac{24{,}000{,}000}{1{,}000{,}000} = 24 \text{ MB} \]
The book therefore occupies about 24 MB. (If the binary convention \(1\,\text{MB} = 1{,}048{,}576\) bytes is used instead, the answer is \(24{,}000{,}000 \div 1{,}048{,}576 \approx 22.89\,\text{MB}\).)
(b) An example of auxiliary (secondary) storage: hard disk drive (also acceptable: flash/USB drive, CD-ROM, DVD, or magnetic tape).
(c) The two main types of computer software with examples:
| Main type | Examples |
|---|---|
| (i) System software | A - Operating system (e.g. Windows) B - Utility program / device driver |
| (ii) Application software | A - Word processor (e.g. Microsoft Word) B - Spreadsheet (e.g. Microsoft Excel) |
Frage 3 Bericht
(a) State two BASIC programming keywords.
(b) Write the following equations in BASIC format:
(i) I = PRT/100: (ii) Y= AX\(_2\) +BX+C; (iii) Y= MX + C
(c) Write a BASIC program that accepts mass and volume of a liquid as input from the User.
The program should compute.and display the density of the liquid. Density = mass volume
(a) Two BASIC programming keywords
- INPUT (used to receive data from the user).
- PRINT (used to display output on the screen).
(Other acceptable keywords: LET, REM, IF, THEN, FOR, END.)
(b) The equations in BASIC format
- (i) \(I = \dfrac{PRT}{100}\) is written as
I = (P * R * T) / 100 - (ii) \(Y = AX^2 + BX + C\) is written as
Y = A * X ^ 2 + B * X + C - (iii) \(Y = MX + C\) is written as
Y = M * X + C
(c) BASIC program to compute the density of a liquid
Density is mass divided by volume, \(D = \dfrac{mass}{volume}\).
10 REM PROGRAM TO CALCULATE DENSITY OF A LIQUID
20 INPUT "ENTER MASS"; M
30 INPUT "ENTER VOLUME"; V
40 D = M / V
50 PRINT "DENSITY OF THE LIQUID = "; D
60 ENDAntwortdetails
(a) Two BASIC programming keywords
- INPUT (used to receive data from the user).
- PRINT (used to display output on the screen).
(Other acceptable keywords: LET, REM, IF, THEN, FOR, END.)
(b) The equations in BASIC format
- (i) \(I = \dfrac{PRT}{100}\) is written as
I = (P * R * T) / 100 - (ii) \(Y = AX^2 + BX + C\) is written as
Y = A * X ^ 2 + B * X + C - (iii) \(Y = MX + C\) is written as
Y = M * X + C
(c) BASIC program to compute the density of a liquid
Density is mass divided by volume, \(D = \dfrac{mass}{volume}\).
10 REM PROGRAM TO CALCULATE DENSITY OF A LIQUID
20 INPUT "ENTER MASS"; M
30 INPUT "ENTER VOLUME"; V
40 D = M / V
50 PRINT "DENSITY OF THE LIQUID = "; D
60 ENDFrage 4 Bericht
(a) (i) What is a network cable?
(ii) State three types of cable used in networking
(b) Write the acronym VSAT in full.
(C) (i) Distinguish between an e-mail address and a website address.
(ii) List examples of each of: (1) e-mail address (2) website address
(a)(i) What is a network cable?
A network cable is a physical transmission medium (a wire or fibre) used to connect two or more computers or network devices together so that data signals can pass between them.
(a)(ii) Three types of cable used in networking
- Twisted-pair cable (for example UTP/STP, used with RJ-45 connectors).
- Coaxial cable.
- Fibre-optic cable.
(b) VSAT in full
VSAT means Very Small Aperture Terminal.
(c)(i) Difference between an e-mail address and a website address
An e-mail address is the unique identifier of an electronic mailbox to which messages are sent; it always contains the @ symbol in the form username@domain. A website address (URL) is the unique location of a web page or site on the Internet that you type into a browser to view the site; it has no @ symbol and usually begins with a protocol such as http:// or www.
(c)(ii) Examples of each
- E-mail address: ada@yahoo.com; info@waec.org.ng
- Website address: www.waecnigeria.org; https://www.google.com
Antwortdetails
(a)(i) What is a network cable?
A network cable is a physical transmission medium (a wire or fibre) used to connect two or more computers or network devices together so that data signals can pass between them.
(a)(ii) Three types of cable used in networking
- Twisted-pair cable (for example UTP/STP, used with RJ-45 connectors).
- Coaxial cable.
- Fibre-optic cable.
(b) VSAT in full
VSAT means Very Small Aperture Terminal.
(c)(i) Difference between an e-mail address and a website address
An e-mail address is the unique identifier of an electronic mailbox to which messages are sent; it always contains the @ symbol in the form username@domain. A website address (URL) is the unique location of a web page or site on the Internet that you type into a browser to view the site; it has no @ symbol and usually begins with a protocol such as http:// or www.
(c)(ii) Examples of each
- E-mail address: ada@yahoo.com; info@waec.org.ng
- Website address: www.waecnigeria.org; https://www.google.com
Frage 5 Bericht
(a) Convert the following numbers to be stated bases:
(i) 125.625, to binary
(ii) 111011.10011, to octal
(b) Given that X = 11011011 and Y= 11101101,
(i) construct the truth table for X, Y Z;
(ii) draw the logic gate of X, Y = Z
(iii) state the value of Z.
(a) Number-base conversions
(i) Convert \(125.625_{10}\) to base 2.
For the integer part, successive division by 2 gives:
| Division | Quotient | Remainder |
|---|---|---|
| 125 ÷ 2 | 62 | 1 |
| 62 ÷ 2 | 31 | 0 |
| 31 ÷ 2 | 15 | 1 |
| 15 ÷ 2 | 7 | 1 |
| 7 ÷ 2 | 3 | 1 |
| 3 ÷ 2 | 1 | 1 |
| 1 ÷ 2 | 0 | 1 |
Reading the remainders from bottom to top gives \(125_{10}=1111101_2\).
For the fractional part:
\(0.625\times2=1.25\), giving 1;
\(0.25\times2=0.5\), giving 0;
\(0.5\times2=1.0\), giving 1.
Therefore, \(0.625_{10}=0.101_2\), and hence
\[\boxed{125.625_{10}=1111101.101_2}\]
(ii) Convert \(111011.10011_2\) to base 8. Group the binary digits in threes from the binary point:
\[111\;011.100\;110_2=73.46_8\]
\[\boxed{111011.10011_2=73.46_8}\]
(b) \(X=11011011\), \(Y=11101101\), and \(Z=X\mathbin{\text{ AND }}Y\).
(i) Truth table for the AND operation
| X | Y | Z = X AND Y |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
(ii) Logic-gate diagram
(iii) Value of \(Z\)
| Bit position | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
|---|---|---|---|---|---|---|---|---|
| X | 1 | 1 | 0 | 1 | 1 | 0 | 1 | 1 |
| Y | 1 | 1 | 1 | 0 | 1 | 1 | 0 | 1 |
| Z | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 |
\[\boxed{Z=11001001_2}\]
Antwortdetails
(a) Number-base conversions
(i) Convert \(125.625_{10}\) to base 2.
For the integer part, successive division by 2 gives:
| Division | Quotient | Remainder |
|---|---|---|
| 125 ÷ 2 | 62 | 1 |
| 62 ÷ 2 | 31 | 0 |
| 31 ÷ 2 | 15 | 1 |
| 15 ÷ 2 | 7 | 1 |
| 7 ÷ 2 | 3 | 1 |
| 3 ÷ 2 | 1 | 1 |
| 1 ÷ 2 | 0 | 1 |
Reading the remainders from bottom to top gives \(125_{10}=1111101_2\).
For the fractional part:
\(0.625\times2=1.25\), giving 1;
\(0.25\times2=0.5\), giving 0;
\(0.5\times2=1.0\), giving 1.
Therefore, \(0.625_{10}=0.101_2\), and hence
\[\boxed{125.625_{10}=1111101.101_2}\]
(ii) Convert \(111011.10011_2\) to base 8. Group the binary digits in threes from the binary point:
\[111\;011.100\;110_2=73.46_8\]
\[\boxed{111011.10011_2=73.46_8}\]
(b) \(X=11011011\), \(Y=11101101\), and \(Z=X\mathbin{\text{ AND }}Y\).
(i) Truth table for the AND operation
| X | Y | Z = X AND Y |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
(ii) Logic-gate diagram
(iii) Value of \(Z\)
| Bit position | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
|---|---|---|---|---|---|---|---|---|
| X | 1 | 1 | 0 | 1 | 1 | 0 | 1 | 1 |
| Y | 1 | 1 | 1 | 0 | 1 | 1 | 0 | 1 |
| Z | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 |
\[\boxed{Z=11001001_2}\]
