By Elimu Assistant Team 
Understanding Computer Systems: Key Questions
Questions
- a) Explain why a computer is able to display the correct time and date when it has just been switched on. (2 mks)
b) Discuss two types of special memories found in a computer system. (4 mks)
c) i) Define a Bus with reference to a computer system. (1 mk)
ii) List two examples of buses. (2 mks)
d) Distinguish between a power cable and an interface cable. (2 mks)
e) Differentiate between the different types of RAM. (4 mks) - a) i) Define a system. (1 mk)
ii) Explain system entropy. (1 mk)
b) State three circumstances that can lead to the development of information systems. (3 mks)
c) Distinguish parallel changeover from straight changeover as used in system implementation. (2 mks)
d) Discuss two fact-finding methods. (4 mks)
e) Differentiate an open system from a closed system. (2 mks)
f) List two responsibilities of a system analyst. (2 mks) - a) State two ways of representing a signed number. (2 mks)
b) Convert110011.0110to Decimal (3 mks)
c) Differentiate between absolute value and base value. (2 mks)
d) Outline two reasons for using the binary system in computers. (2 mks)
e) Perform111011001000_2 – 11011011001_2using one’s complement and convert your answer to Hexadecimal. (4 mks)
Answered
In this blog post, we’ll explore some fundamental questions about computer systems, information systems, and binary number systems. Whether you’re a student, tech enthusiast, or someone looking to deepen your understanding of computing, this guide will provide clear and concise answers to common questions.
1. Why Does a Computer Display the Correct Time and Date When Switched On?
When you turn on your computer, it displays the correct time and date because of a special memory called the Complementary Metal-Oxide Semiconductor (CMOS). This memory is powered by a small battery (often called the CMOS battery) even when the computer is off. The CMOS stores essential system information, including the date and time, ensuring it remains accurate.
2. Types of Special Memories in a Computer System
Computers use various types of special memories to optimize performance and functionality. Two key examples include:
- Cache Memory: A high-speed memory located inside the processor. It stores frequently accessed data to speed up processing.
- Buffers: Temporary storage areas found in input/output devices. They help manage data flow between devices with different speeds.
3. What is a Bus in a Computer System?
A bus is an electronic pathway that connects different components of a computer system, allowing them to communicate. Examples of buses include:
- Address Bus: Carries memory addresses for data transfer.
- Data Bus: Transfers actual data between components.
- Control Bus: Sends control signals to manage operations.
4. Power Cable vs. Interface Cable
- Power Cable: Transmits electrical power from a source (like a wall socket) to the computer.
- Interface Cable: Connects peripheral devices (e.g., printers, monitors) to the computer system for data transfer.
5. Types of RAM
RAM (Random Access Memory) comes in different types, each with unique characteristics:
- Static RAM (SRAM): Faster and more expensive, used in cache memory.
- Dynamic RAM (DRAM): Slower but cheaper, used as the main memory in computers.
6. What is a System?
A system is a set of organized components that work together within a defined boundary to achieve specific goals.
7. System Entropy Explained
System entropy refers to the gradual decay of a system over time. As user requirements change and technology evolves, a system may become less effective or obsolete.
8. Circumstances Leading to Information System Development
Information systems are developed under three main circumstances:
- New Opportunities: To leverage emerging technologies or market trends.
- Problems: To address inefficiencies or challenges in existing systems.
- Directives: To comply with new regulations or organizational policies.
9. Parallel Changeover vs. Straight Changeover
- Parallel Changeover: Both old and new systems run simultaneously until users are confident in the new system.
- Straight Changeover: The old system is replaced immediately by the new one.
10. Fact-Finding Methods
Two common methods for gathering system requirements are:
- Interviews: Engaging with stakeholders to understand their needs.
- Questionnaires: Collecting feedback and opinions from users through structured forms.
11. Open System vs. Closed System
- Open System: Interacts with its environment, exchanging information and resources.
- Closed System: Operates independently, without external interactions.
12. Responsibilities of a System Analyst
A system analyst is responsible for:
- Reviewing existing systems and recommending improvements.
- Collaborating with programmers to design and implement new systems.
13. Representing Signed Numbers
Signed numbers can be represented using:
- One’s Complement: Inverts all bits of a binary number.
- Two’s Complement: Adds 1 to the one’s complement for a more efficient representation.
14. Binary to Decimal Conversion
To convert 110011.0110 to decimal:
- Calculation:
1×25+1×24+0×23+0×22+1×21+1×20+0×2−1+1×2−2+1×2−3+0×2−41×25+1×24+0×23+0×22+1×21+1×20+0×2−1+1×2−2+1×2−3+0×2−4
=32+16+0+0+2+1+0+0.25+0.125+0=51.375=32+16+0+0+2+1+0+0.25+0.125+0=51.375
15. Absolute Value vs. Base Value
- Absolute Value: The magnitude of a number, ignoring its sign.
- Base Value: The positional value of a digit in a number system (e.g., 10 in decimal, 2 in binary).
16. Why Use Binary in Computers?
The binary system is used in computers because:
- It simplifies the design of electronic circuits (ON/OFF states).
- Digital devices based on binary are more reliable, compact, and energy-efficient.
17. Binary Subtraction Using One’s Complement
To perform 111011001000_2 – 11011011001_2:
- Find the one’s complement of the subtrahend:
1101101100111011011001 → 0010010011000100100110 - Add to the minuend:
111011001000+00100100110=111111101110111011001000+00100100110=111111101110 - Convert to hexadecimal:
1111111011102=FEE161111111011102=FEE16
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