SC015 Computer Science Examination Revision Flashcards

Comprehensive practice flashcards covering the SC015 Computer Science syllabus including Information Processing Cycle, Number System conversions, Information Coding Schemes, Logic Gates and Truth Tables, Network Architectures, Classifications, Internet Addressing, Ethics, Netiquette, and the System Development Life Cycle (SDLC).

According to the exam guidelines for the Information Processing Cycle (LO 1.1b), what is the required rule when writing an activity?

Always start each answer with an operation verb followed by the data or information (Operation verb + data/information). Examples: read/accept data for Input, calculate/verify/update for Process, and display/show/print for Output.

In the 2023/2024 scenario where Ali withdraws RM100 at an automated teller machine (ATM), what are two valid activities each for Input, Process, and Output operations?

Input:

• Read bank card information such as name
• Read account type
• Read transaction type

Process:

• Verify the card
• Verify the PIN number
• Calculate/verify the balance
• Deduct/update the balance

Output:

• Print/show/display message or balance
• Eject/dispense bank card
• Dispense the money
• Dispense/issue/print the receipt

In the 2024/2025 CaloriX mobile application scenario, what are two valid activities each for Input, Process, and Output operations?

Input:

• Read number of steps
• Capture/upload/take food photos
• Read initial weight

Process:

• Calculate/estimate calories per day
• Calculate/estimate/verify calories per photo
• Verify optimal diet
• Measure/predict/calculate time/duration needed to obtain ideal weight
• Generate/create meal plan

Output:

• Display/show recommendation/suggestion/advisory of meal plan
• Display/show relevant photos
• Display/show time/duration needed to gain ideal weight
• Display weight increment/decrement

In the 2025/2026 scenario where Johan calculates the average BMI of students in his class, what are two valid activities each for Input, Process, and Output operations?

Input:

• Read the number of students
• Read weight
• Read height

Process:

• Calculate/compute BMI of each student
• Calculate/compute total BMI of all students
• Calculate/compute average BMI
• Verify/determine the value entered from the user

Output:

• Display/show/print the error message
• Display/show/print average BMI
• Display/show/print the BMI

How is the binary whole number $110011_2$ converted into decimal?

By multiplying each binary digit by its corresponding positional weight of base $2$: $(1 \times 2^5) + (1 \times 2^4) + (0 \times 2^3) + (0 \times 2^2) + (1 \times 2^1) + (1 \times 2^0)$$= 32 + 16 + 0 + 0 + 2 + 1$$= 51_{10}$

How is the binary whole number $101010_2$ converted into decimal?

By multiplying each binary bit by powers of $2$: $(1 \times 2^5) + (0 \times 2^4) + (1 \times 2^3) + (0 \times 2^2) + (1 \times 2^1) + (0 \times 2^0)$$= 32 + 0 + 8 + 0 + 2 + 0$$= 42_{10}$

How is the hexadecimal value $5\text{A}55_{16}$ converted to decimal?

Substitute hex digit $\text{A}$ with $10$, then expand by powers of $16$: $(5 \times 16^3) + (10 \times 16^2) + (5 \times 16^1) + (5 \times 16^0)$$= (5 \times 4096) + (10 \times 256) + (5 \times 16) + (5 \times 1)$$= 20480 + 2560 + 80 + 5$$= 23125_{10}$

How is the hexadecimal value $\text{B0FA}_{16}$ converted to decimal?

Substitute hex digits $\text{B} = 11$ and $\text{F} = 15$ and $\text{A} = 10$, then expand: $(11 \times 16^3) + (0 \times 16^2) + (15 \times 16^1) + (10 \times 16^0)$$= (11 \times 4096) + 0 + (15 \times 16) + (10 \times 1)$$= 45056 + 0 + 240 + 10$$= 45306_{10}$

What is the workflow rule for converting between hexadecimal and binary numbers?

1. Hexadecimal to binary: Convert each single hexadecimal digit into a 4-bit binary equivalent from right to left.
2. Binary to hexadecimal: Group binary digits into sets of 4 bits starting from right to left, then convert each 4-bit group into its single hexadecimal digit.

What is the binary conversion of the hexadecimal value $78_{16}$?

Convert each digit into a 4-bit group:

• $7 = 0111_2$
• $8 = 1000_2$ Combining the groups yields $01111000_2$ (or $1111000_2$).

What is the binary conversion of the hexadecimal value $\text{D0B1}_{16}$?

Convert each hex character to 4 binary bits ($\text{D} = 13$, $0 = 0$, $\text{B} = 11$, $1 = 1$):

• $\text{D} \rightarrow 1101_2$
• $0 \rightarrow 0000_2$
• $\text{B} \rightarrow 1011_2$
• $1 \rightarrow 0001_2$ Result: $1101000010110001_2$

What is the hexadecimal equivalent of the 16-bit binary string $1010001111101100_2$?

Divide the bits into 4-bit nibbles from right to left:

• $1010_2 = 10 = \text{A}_{16}$
• $0011_2 = 3 = 3_{16}$
• $1110_2 = 14 = \text{E}_{16}$
• $1100_2 = 12 = \text{C}_{16}$ Result: $\text{A3EC}_{16}$

Differentiate between the EBCDIC and Unicode coding schemes based on number of bits, number of characters represented, and context of use.

• Number of bits: EBCDIC uses $8\text{ bits}$ per character; Unicode uses $16\text{ bits}$ per character.
• Number of characters: EBCDIC represents $256$ ($2^8$) characters; Unicode represents $65536$ ($2^{16}$) characters.
• Context of use: EBCDIC is used on IBM mainframe computers or high-end servers; Unicode is implemented across multiple operating systems (Windows, Mac OS X, Linux) to represent all written human languages.

Which coding scheme is suitable for representing characters in English versus Korean, and why?

• English: ASCII / Extended ASCII, because it uses $8\text{ bits}$ to represent up to $256$ characters, which is sufficient for English letters and symbols.
• Korean: Unicode, because it uses $16\text{ bits}$ to represent up to $65536$ characters, allowing it to encompass complex characters and non-Latin written scripts such as Korean.

Calculate the total number of bits and bytes required to store the string "Never Lose" using both the Unicode and EBCDIC coding schemes.

The string "Never Lose" has $10\text{ characters}$ (including the space).

• Unicode: $10 \times 16 = 160\text{ bits}$; $160 / 8 = 20\text{ bytes}$
• EBCDIC: $10 \times 8 = 80\text{ bits}$; $80 / 8 = 10\text{ bytes}$

What is the order of precedence from highest to lowest for logical operators in Boolean expressions?

1. Parentheses ( )
2. NOT, NAND (same precedence, left to right)
3. NOR, XOR, XNOR (same precedence, left to right)
4. AND
5. OR

Based on the provided logic circuit diagram, what is the resulting Boolean expression for output $Y$?

$$Y = (A \cdot B)' + (B \oplus C)'$$

Based on the logic circuit shown in FIGURE 2.1, what is the complete Boolean expression for output $X$?

$$X = (A'B' + AB) \cdot C$$

How can the logic circuit for $X = (A'B' + AB) \cdot C$ be simplified using only two types of logic gates?

The term $(A'B' + AB)$ is equivalent to the XNOR operation $(A \oplus B)'$. Therefore, it can be simplified using an XNOR gate receiving inputs $A$ and $B$, whose output connects directly into a 2-input AND gate along with input $C$, yielding $X = (A \oplus B)' \cdot C$.

What are the Boolean expressions and logic gates corresponding to the following two logic statements?

1. Output $Y$ is True (1) if inputs $A$ and $B$ are the same, and False (0) if they differ.
2. Output $Y$ is True (1) if inputs $A$ and $B$ are False (0), and False (0) if any input is True.

1. XNOR Gate: $Y = (A \oplus B)'$
2. NOR Gate: $Y = (A + B)'$

Based on FIGURE 2.2, determine the intermediate expressions for outputs $C$ and $D$, and the final output $Q$.

• $C = (A \cdot B)'$ (NAND gate)
• $D = A \oplus B$ (XOR gate)
• $Q = (C \oplus D)' = ((A \cdot B)' \oplus (A \oplus B))'$ (XNOR gate)

In the 2023/2024 scenario for traveling from Kuala Lumpur to Bandar Melaka (O) via Expressway (U) or Federal Road (P), what is the derived Boolean expression?

$O = P + U$ Where Federal Road $P = (S \cdot A) \cdot D'$ and Expressway $U = B \cdot K$. Thus: $O = ((S \cdot A) \cdot D') + (B \cdot K)$

In an elderly monitoring system, an alert is triggered (X) if a fever is detected (F), or the bed is not occupied (B'), or the emergency button is pressed (E). What is the Boolean expression?

$$X = F + B' + E$$

Compare Client-Server and Peer-to-Peer (P2P) network architectures in terms of centralization, file management, and security control.

• Client-Server: Centralized model where a dedicated server controls resources, data security, and file management; all clients request services from the central server; security is centrally controlled by an administrator.
• Peer-to-Peer (P2P): Decentralized model where every computer acts as both service provider (server) and consumer (client); no central repository for files; users manage security on their own individual machines.

State two drawbacks of a Peer-to-Peer (P2P) network architecture.

1. Vulnerable to security threats due to direct peer-to-peer communication without centralized authentication.
2. Lack of a central repository makes file management and backups difficult.
3. Network speed and performance can decrease significantly as more peers participate and share files.

In a Peer-to-Peer network, what happens to User A's computer if User B's computer suffers a virus attack?

The virus will only infect User A's computer if an infected file is transferred from Computer B and executed/opened on Computer A. If files are not shared, or if User A receives but does not execute the infected files, User A's computer remains safe.

Differentiate between a Local Area Network (LAN) and a Wide Area Network (WAN) based on area of coverage and ownership.

• Area of Coverage: LAN covers devices within a limited geographical area (e.g., a home, school computer lab, single building). WAN spans a broad geographical region (e.g., a city, country, or across the globe).
• Ownership: LAN is typically owned, managed, and operated by a single individual organization. WAN exists under collective ownership, multiple telecommunications providers, or public/consortium management over long distances.

Differentiate between Intranet and Extranet based on accessibility of information.

• Intranet: Accessible exclusively by an organization's internal employees and authorized internal personnel.
• Extranet: Accessible by authorized internal employees as well as designated external partners, suppliers, vendors, or customers.

What are three recognized disadvantages of the Internet according to the course notes?

1. Privacy and security issues: Personal information is vulnerable to data theft, hacking, and identity fraud.
2. Addiction and time wasting: Users may over-consume digital entertainment/gaming, leading to neglected duties.
3. Misinformation and fake news: The spread of unverified or fraudulent content can create confusion and panic.

What are the primary differences between IPv4 and IPv6 in terms of address length, number of groups/octets, and number system representation?

• Address length: IPv4 is $32\text{ bits}$; IPv6 is $128\text{ bits}$.
• Number of groups/octets: IPv4 consists of $4\text{ groups (octets)}$ separated by periods; IPv6 consists of $8\text{ groups}$ separated by colons.
• Number system: IPv4 uses decimal numbers (range $0 - 255$ per octet); IPv6 uses hexadecimal notation (range $0 - \text{FFFF}$ per group).

Why was IPv6 introduced to replace IPv4?

To overcome the exhaustion of available 32-bit IPv4 addresses by providing a vast address pool of $2^{128}$ unique addresses, accommodating the rapid growth of Internet-connected devices, smartphones, and IoT.

What is the relationship between an IP address and a domain name, and what is the role of the Domain Name Server (DNS)?

A domain name is the human-readable text alias of a numerical IP address. A Domain Name Server (DNS) translates and maps the domain name entered by a user into its corresponding IP address so network routing can occur.

Identify the four components labeled (i), (ii), (iii), and (iv) in the web address shown.

(i) Protocol (http) (ii) Server address / domain name (www.nsp.biz.my) (iii) Pathway (/newproject/) (iv) Webpage name / document file (login.htm)

Differentiate between HTTP and HTTPS in terms of security and usage.

• HTTP (Hypertext Transfer Protocol): Unencrypted data transmission suitable only for non-sensitive public web content.
• HTTPS (Hypertext Transfer Protocol Secure): Encrypted communication providing data security, confidentiality, and integrity; essential for sensitive data, online banking, and e-commerce.

What is Computer Ethics, and what are its six recognized areas?

Computer Ethics refers to moral guidelines that govern the use of computers, mobile devices, information systems, and related technologies. Its six areas are:

1. Information Accuracy
2. Green Computing
3. Software Piracy
4. Codes of Conduct
5. Information Privacy
6. Intellectual Property Rights

Identify the specific area of Computer Ethics illustrated by each of the following scenarios:

1. A student uses ChatGPT to write an academic assignment without fact-checking or originality.
2. Someone downloads another person's photo from social media to create deepfakes and repost them.
3. Administrative staff use student directory records to promote private tutoring businesses.

1. Information Accuracy
2. Information Privacy
3. Information Privacy

What is Netiquette, and what are two key rules when participating in online forums or instant messaging?

Netiquette is the code of acceptable behaviors users should adhere to while communicating on the Internet. Key rules include:

• Avoid typing in ALL CAPITAL LETTERS, as it represents shouting.
• Use proper grammar, spelling, and punctuation.
• Be polite, avoid offensive language, and do not post flames.
• Be forgiving of other people's unintended spelling or grammatical errors.

What are the five phases of the System Development Life Cycle (SDLC) in chronological order?

1. Planning
2. Analysis
3. Design
4. Implementation
5. Support & Security

What are the main activities and deliverables of the SDLC Planning phase?

Activities:

• Review and approve project requests
• Prioritize project requests
• Allocate resources (money, people, equipment)
• Form the project development team

Deliverables:

• List of project requests, cost estimates, team roster, schedule/milestones, Gantt charts, and PERT charts.

What are the two major sub-stages of the SDLC Analysis phase?

1. Preliminary Investigation: Gathers initial information, studies the core problem, and produces a Feasibility Report.
2. Detailed Analysis: Assesses existing workflows, determines specific user requirements, and constructs models (ERD, DFD, Use Case diagrams).

What are the four conversion methods used in the SDLC Implementation phase to deploy a new system?

1. Direct conversion: Shuts down the old system completely and immediately activates the new system.
2. Parallel conversion: Runs the old system alongside the new system simultaneously until the new system is proven reliable.
3. Phased conversion: Implements modules or components of the new system in progressive stages.
4. Pilot conversion: Introduces the entire system into only one selected department or branch before organization-wide rollout.

Identify and define the four types of system maintenance carried out during Phase 5 (Support & Security) of the SDLC.

1. Corrective maintenance: Diagnoses and fixes existing bugs or system errors.
2. Adaptive maintenance: Implements changes to adapt to updated hardware, software environments, or new regulatory requirements.
3. Perfective maintenance: Optimizes performance, improves user interfaces, and enhances efficiency.
4. Preventive maintenance: Reduces the probability of future problems through routine checkups and system tuning.