Computer Organisation Exercise Solutions | KalviGavani

Computer Organisation: Exercise Solutions

How to Use This Page

Read the Samacheer Kalvi textbook Chapter 3 (Computer Organisation) first. Then use this page to revise: attempt the textbook questions on your own, then compare with the model answers below. Pay special attention to the Common Mistakes section and the Exam Checklist before your test.

Key Concepts (Quick Recap)

I. Choose the Correct Answer (MCQ)

Q1. The component of the CPU that performs arithmetic and logical operations is:

(a) Control Unit (b) Register (c) ALU ✓ (d) Memory

Q2. Which of the following is a volatile memory?

(a) ROM (b) Hard Disk (c) RAM ✓ (d) CD

Q3. The main printed circuit board in a computer is called:

(a) Processor (b) Motherboard ✓ (c) Hard Disk (d) RAM

Q4. Which memory is fastest in a computer?

(a) Hard Disk (b) RAM (c) Cache Memory ✓ (d) Pen Drive

Q5. MICR stands for:

(a) Magnetic Ink Character Recognition ✓ (b) Magnetic Input Character Reader (c) Magnetic Ink Code Recognition (d) Memory Ink Character Recognition

Q6. Which of the following is a secondary storage device?

(a) RAM (b) Cache (c) ROM (d) Hard Disk ✓

Q7. The bus that carries memory addresses from the CPU is called:

(a) Data Bus (b) Control Bus (c) Address Bus ✓ (d) System Bus

Q8. OMR is used to:

(a) Read magnetic characters (b) Read barcodes (c) Detect marks on paper ✓ (d) Convert text to speech

Q9. Which port is used to connect a printer?

(a) USB Port ✓ (b) HDMI Port (c) VGA Port (d) Ethernet Port

Q10. SSD stands for:

(a) Solid State Device (b) Solid Storage Drive (c) Solid State Drive ✓ (d) System Storage Device

II. Very Short Answer Questions (2 Marks)

Q1. What is the function of the ALU?

The ALU receives data from registers or memory, processes it, and sends the result back through the accumulator or to memory.

Q2. What are registers? Name any two registers.

Other registers include the Memory Address Register (MAR) and Instruction Register (IR).

Q3. Differentiate between RAM and ROM.

Q4. What is cache memory?

Q5. What is the function of the Control Unit?

The Control Unit does not process data itself — it manages and synchronises the activities of all other units.

Q6. What is a port? Name any two types.

Other types include VGA port, Ethernet port, PS/2 port, and audio port.

III. Short Answer Questions (3 Marks)

Q1. Explain the components of the CPU.

1. Arithmetic and Logic Unit (ALU): Performs all arithmetic operations (addition, subtraction, multiplication, division) and logical comparisons (greater than, less than, equal to). It is the computational engine of the CPU.

2. Control Unit (CU): Directs and coordinates all computer operations. It fetches instructions from memory, decodes them, and sends control signals to the ALU, memory, and I/O devices to execute the instructions. It acts as the manager of the entire system.

3. Registers: Small, high-speed memory locations inside the CPU used to temporarily hold data and instructions during processing. Important registers include the Accumulator (stores results), Program Counter (holds next instruction address), Memory Address Register (holds memory addresses), and Instruction Register (holds current instruction).

Q2. Describe the different types of secondary storage devices.

1. Hard Disk Drive (HDD): Uses magnetic disks (platters) that rotate under read/write heads. Offers large storage capacity (up to several TB) at low cost. Has moving parts, so it is slower than SSD and more prone to physical damage.

2. Solid State Drive (SSD): Uses flash memory with no moving parts. Much faster than HDD in read/write operations, more durable, and consumes less power. More expensive per GB than HDD. Commonly used as the primary drive in modern laptops.

3. CD (Compact Disc): Optical storage medium that stores up to 700 MB. Available as CD-ROM (read-only), CD-R (write once), and CD-RW (rewritable). Uses laser technology to read and write data.

4. DVD (Digital Versatile Disc): Similar to CD but with much higher capacity — single-layer DVDs hold 4.7 GB and dual-layer DVDs hold 8.5 GB. Used for storing videos, software, and large data files.

5. Pen Drive (USB Flash Drive): Small, portable flash storage device that connects via USB. Available in capacities from a few GB to over 256 GB. Convenient for transferring data between computers.

Q3. Explain the different types of memory in a computer.

Q4. Write a short note on input devices — MICR, OMR, and OCR.

1. MICR (Magnetic Ink Character Recognition): Reads characters printed with special magnetic ink. Primarily used in the banking industry for processing cheques. The magnetic ink allows characters (numbers 0-9 and four special symbols) to be read even if they are covered by stamps or signatures. It ensures high accuracy and security in cheque processing.

2. OMR (Optical Mark Recognition): Detects the presence or absence of marks (filled circles or rectangles) on a printed paper. Widely used for evaluating objective-type answer sheets in examinations, surveys, and lottery forms. It reads the position of marks, not the actual characters. OMR is fast and accurate for large-scale data collection.

3. OCR (Optical Character Recognition): Converts printed or handwritten text images into machine-readable digital text. Used for digitising books, documents, and forms. Unlike OMR which detects only marks, OCR recognises individual characters and can convert them into editable text. Commonly used in document scanning and data entry applications.

Q5. What is a motherboard? Describe its main components.

1. CPU Socket — holds the processor and connects it to the motherboard. 2. RAM Slots — slots where memory modules (DIMMs) are installed. 3. BIOS Chip — contains firmware that initialises hardware during boot-up. 4. Expansion Slots — PCI and PCIe slots for adding graphics cards, sound cards, and network cards. 5. Storage Connectors — SATA and M.2 connectors for hard drives and SSDs. 6. Power Connector — connects the power supply unit to the motherboard. 7. Ports — USB, HDMI, VGA, audio, Ethernet, and PS/2 ports for external devices. 8. Chipset — manages data flow between the CPU, memory, and peripherals. 9. Battery (CMOS) — maintains system settings like date and time when the computer is off.

IV. Long Answer Questions (5 Marks)

Q1. Explain the organisation of a computer with a neat block diagram.

Data Flow: 1. Input Unit feeds data into the CPU. 2. Control Unit fetches and decodes instructions, directs data flow. 3. ALU processes data — arithmetic and logical operations. 4. Registers hold data temporarily during processing. 5. Primary Memory stores data and programs currently in use. 6. Output Unit displays or produces the results. 7. Secondary Memory provides permanent storage for data and programs.

Q2. Explain the different types of input devices in detail.

1. Keyboard: The most common input device. It has keys for letters (A-Z), numbers (0-9), special characters, and function keys. Types include mechanical keyboards (physical switches), membrane keyboards (pressure pads), and virtual keyboards (on-screen). Used for typing text, entering commands, and data entry.

2. Mouse: A pointing device that controls the cursor on the screen. Types include optical mouse (uses LED light), laser mouse (uses laser for tracking), and wireless mouse (uses Bluetooth or RF). Actions include click, double-click, right-click, drag, and scroll. Essential for GUI-based operating systems.

3. Scanner: Converts physical documents, photographs, and images into digital format. Uses a light sensor to capture the image. Types include flatbed scanner (glass surface), sheet-fed scanner (paper is fed through), and handheld scanner. Resolution is measured in DPI (dots per inch).

4. MICR (Magnetic Ink Character Recognition): Reads characters printed with special magnetic ink. Primarily used in banking for cheque processing. The E-13B font is used for numbers 0-9 and four special symbols. Magnetic reading ensures accuracy even if the cheque is stamped or has signatures over the characters.

5. OMR (Optical Mark Recognition): Detects marks (filled circles or rectangles) on printed forms. Used extensively for evaluating objective answer sheets in competitive examinations, surveys, and feedback forms. A light beam scans the form and detects the position and intensity of marks. It is fast, accurate, and suitable for large-scale data collection.

6. OCR (Optical Character Recognition): Converts printed or handwritten text images into editable digital text. Used for digitising books, documents, and forms. Unlike OMR which detects only marks, OCR recognises individual characters. Modern OCR can handle multiple languages and fonts. Used in document management, data entry, and accessibility tools.

7. Barcode Reader: Scans barcode patterns (parallel lines of varying widths) printed on products. Used in retail stores, supermarkets, libraries, and warehouses for quick product identification and pricing. The reader uses a laser or LED to scan the barcode and converts it into a digital code that the computer can process.

Q3. Explain the different types of output devices in detail.

1. Monitor (Visual Display Unit): The most common output device, displays text, images, and video on screen. Types include:

• CRT (Cathode Ray Tube) — older, bulky monitors using electron beams; now largely obsolete.
• LCD (Liquid Crystal Display) — thin, lightweight, energy-efficient monitors used in most modern computers and laptops.
• LED (Light Emitting Diode) — similar to LCD but uses LED backlighting for better colour and contrast.
• OLED (Organic LED) — each pixel emits its own light; provides superior colour and contrast.

Key specifications: screen size (measured diagonally), resolution (e.g., 1920x1080), and refresh rate (e.g., 60 Hz).

2. Printer: Produces hard copy (paper) output. Types include:

• Dot Matrix Printer — uses pins to strike an inked ribbon; produces low-quality output; used in billing and invoicing where carbon copies are needed.
• Inkjet Printer — sprays tiny droplets of ink onto paper; produces good-quality colour output at moderate cost; common for home use.
• Laser Printer — uses laser beam and toner powder; produces high-quality, fast output; ideal for offices with high-volume printing needs.

3. Speaker: Converts digital audio signals into sound waves. Used for listening to music, videos, notifications, and multimedia presentations. Types include external speakers, built-in laptop speakers, headphones, and earphones. Connected via audio jack, USB, or Bluetooth.

4. Projector: Projects computer display onto a large screen or wall for presentations, classroom teaching, and home theatre. Types include LCD projectors and DLP (Digital Light Processing) projectors. Connected via VGA, HDMI, or wirelessly.

5. Plotter: A specialised output device that draws continuous lines to produce large-format graphics such as architectural blueprints, engineering drawings, and maps. Types include pen plotters and inkjet plotters. Used in CAD (Computer-Aided Design) applications.

Q4. Explain the different types of buses and ports in a computer.

Buses: A bus is a set of parallel wires (communication pathway) that connects different components of a computer and allows data, addresses, and control signals to travel between them. There are three types:

1. Address Bus:

• Carries memory addresses from the CPU to memory or I/O devices.
• Unidirectional — flows from CPU outward.
• The width (number of lines) determines the maximum addressable memory. For example, a 32-bit address bus can address 2^32 = 4 GB of memory.
• When the CPU needs to read or write data, it places the target address on the address bus.

2. Data Bus:

• Carries actual data between the CPU, memory, and I/O devices.
• Bidirectional — data can flow in both directions.
• The width determines how much data can be transferred at once. A 64-bit data bus transfers 64 bits per cycle.
• All data, whether instructions or operands, travels on the data bus.

3. Control Bus:

• Carries control signals from the CPU to coordinate operations.
• Bidirectional — carries signals in both directions.
• Important control signals include: Read/Write (indicates whether the operation is read or write), Clock (synchronises operations), Interrupt (signals from I/O devices), and Bus Request/Grant (manages bus access among multiple devices).

Ports: A port is a socket on the computer used to connect external devices. Common ports include:

Modern computers increasingly use USB-C and Thunderbolt ports which combine data, video, and power in a single connector.

Common Mistakes to Avoid

• Confusing the ALU (performs calculations) with the Control Unit (directs operations) — the ALU computes; the CU manages.
• Saying RAM is non-volatile — RAM is volatile and loses data when power is off; ROM is non-volatile.
• Confusing cache memory with RAM — cache is smaller, faster, and sits between the CPU and RAM.
• Writing that the address bus carries data — the address bus carries memory addresses only; data travels on the data bus.
• Stating that SSD uses magnetic disks — SSDs use flash memory with no moving parts; HDDs use magnetic platters.
• Mixing up MICR, OMR, and OCR: MICR reads magnetic ink characters (cheques), OMR detects marks on paper (answer sheets), OCR recognises printed/handwritten text (document scanning).
• Forgetting that the data bus is bidirectional while the address bus is unidirectional.
• Confusing ports with buses — ports are physical connectors for external devices; buses are internal communication pathways on the motherboard.
• Writing that ROM allows read and write operations — ROM is read-only; only RAM allows both read and write.
• Listing barcode reader as an output device — it is an input device that scans product information.
• Omitting registers when describing CPU components — registers are essential internal CPU storage locations.
• Saying cache memory is secondary storage — cache is primary memory, located close to the CPU for speed.

Exam Checklist

• [ ] Can you draw and label the block diagram of computer organisation?
• [ ] Can you explain the three components of the CPU (ALU, CU, Registers) with their functions?
• [ ] Can you distinguish between RAM, ROM, and Cache memory?
• [ ] Can you list and explain at least five secondary storage devices (HDD, SSD, CD, DVD, Pen Drive)?
• [ ] Can you explain MICR, OMR, and OCR with their full forms and uses?
• [ ] Can you name and explain the three types of buses (Address, Data, Control)?
• [ ] Can you list at least five types of ports and their uses?
• [ ] Can you describe the components of a motherboard?
• [ ] Can you explain input devices (keyboard, mouse, scanner, barcode reader) and output devices (monitor, printer, speaker, projector)?
• [ ] Can you distinguish between primary memory and secondary memory?
• [ ] Do you know the full forms of MICR, OMR, OCR, SSD, HDD, USB, HDMI, VGA, RAM, ROM, and BIOS?
• [ ] Can you explain the difference between CRT, LCD, LED, and OLED monitors?
• [ ] Can you compare dot matrix, inkjet, and laser printers?