May 2025 (Regular) Examination

Concept: Memory hierarchy organises storage from fastest-smallest-expensive (top) to slowest-largest-cheap (bottom).

1. CPU Registers: Tiny (32–64 bit) storage inside the CPU. Access time: <1 ns. Holds operands currently being processed.
2. Cache (L1/L2/L3): SRAM on or near the CPU die. Stores recently/frequently used data to prevent going to slower RAM.
3. Main Memory (RAM): DRAM, GBs in size, holds the active OS and all running processes.
4. Virtual Memory: Uses part of the SSD/HDD as an extension of RAM (swap space). When RAM is full, the OS pages out least-used memory blocks to disk.

• Speed: SSDs use NAND flash with no moving parts — sequential read up to 550 MB/s (SATA) or 7000 MB/s (NVMe) vs ~150 MB/s for HDD.
• Access time: SSD random access ~0.1 ms vs HDD ~10 ms (no seek delay or rotational latency).
• Durability: No mechanical parts means SSDs withstand shock, vibration, and drops much better.
• Silent operation: No spinning platters or moving heads — completely silent.
• Power efficiency: SSDs consume 2–3 W vs 6–15 W for HDDs, extending laptop battery life.

Hardware Architecture (Von Neumann Architecture) typically consists of:

1. Central Processing Unit (CPU): The brain of the computer. It contains the Control Unit (CU) which manages instructions, the Arithmetic Logic Unit (ALU) for calculations, and Registers for rapid temporary storage.
2. Memory Unit (RAM & ROM): Primary memory used to store data and instructions that are currently being processed by the CPU.
3. Input/Output (I/O) Devices: Input devices (keyboard, mouse) allow users to send data to the system. Output devices (monitor, printer) display the processed results.
4. System Bus: The communication channels (Data Bus, Address Bus, Control Bus) that link the CPU, Memory, and I/O components together for data transfer.

• Firmware: Software that is permanently programmed into a hardware device's read-only memory (ROM/Flash). It provides the low-level control for the device's specific hardware.
• Example: BIOS/UEFI on a motherboard, or code inside a TV remote.
• Difference from Software: Software refers to high-level programs that users interact with (OS, applications) and are loaded into RAM from secondary storage. Firmware is tightly coupled with hardware and rarely updated, acting as the fundamental interface between hardware and higher-level software.

• Scope of characters: ASCII supports only 128 characters (7-bit), sufficient for English but inadequate for global applications. Unicode (version 15) defines over 149,000 characters spanning 161 scripts — Latin, Arabic, Devanagari, CJK ideographs, and emoji.
• UTF-8 encoding: The most common Unicode encoding. fully backward compatible with ASCII. Uses 1 byte for ASCII-compatible characters, 2–4 bytes for others.
• Internationalisation (i18n): Multilingual apps must display user interfaces, store user data, and process input in any language. Unicode provides a single unified standard, eliminating the need for multiple encoding systems.

• Definition: An Instruction Set Architecture (ISA) is the complete set of machine-level instructions that a CPU can execute. It is the contract between hardware designers and software (compiler) writers.
• Software-hardware bridge: High-level language code (C/Python) is compiled into ISA instructions. The CPU's hardwired circuits execute those instructions directly. Example: int c = a+b compiles to ADD R1, R2 -> R3 in ARM ISA.
• Instruction format: Each instruction has an opcode (what to do) and operands (what to do it on — registers, immediate values, or memory addresses).

1. Fetch: PC value is placed on the address bus. Memory returns the instruction at that address. The instruction is stored in IR. PC is incremented to point to the next instruction.
2. Decode: The Control Unit examines the opcode in IR. It generates internal control signals: which ALU operation to perform, which registers to use, whether to read/write memory.
3. Execute: The ALU performs the operation (add, subtract, compare). Data may be read from or written to registers or RAM. For branch instructions, PC may be updated to a new address.
4. Write-back: The result is stored in the destination register or memory location.

Example: Add 0101 (5) and 0011 (3). Expected result: 1000 (8).

• Step 1 — Bit 0 (LSB): 1 + 1 = 10 -> sum bit = 0, carry = 1
• Step 2 — Bit 1: 0 + 1 + carry(1) = 10 -> sum bit = 0, carry = 1
• Step 3 — Bit 2: 1 + 0 + carry(1) = 10 -> sum bit = 0, carry = 1
• Step 4 — Bit 3 (MSB): 0 + 0 + carry(1) = 01 -> sum bit = 1, carry = 0

Result: 1000 (binary) = 8 (decimal). The carry-out from bit 3 is 0, so no overflow.

• Client-Server Network: A dedicated server provides resources/services; clients request them. The server handles authentication, access control, storage, and backups centrally.
  • Advantages: Centralised security, easy to scale, reliable data backup, audit logging.
  • Disadvantages: Higher cost (server hardware), single point of failure (if not redundant).
• Peer-to-Peer (P2P) Network: Each device acts as both client and server.
  • Advantages: Low cost, easy to set up for small groups.
  • Disadvantages: Decentralised security, difficult to scale, hard to manage.
• Recommendation: Client-Server is far better for a multi-city company due to centralized management, reliable backups, and consistent security features.

• (i) Create a directory: mkdir (e.g., mkdir reports)
• (ii) List files and subfolders: ls -la (lists all including hidden, with long format showing permissions)
• (iii) Copy contents: cp (e.g., cp file.txt backup/)
• (iv) Change access permissions: chmod (e.g., chmod 755 script.sh)

• Star Topology: All devices connect to a central switch/hub. Most common in LANs. Advantages: easy to add/remove devices, failure of one node doesn't affect others. Disadvantage: central switch is single point of failure.
• Mesh Topology: Every device is connected to every other device (full mesh) or to several others (partial mesh). Advantages: highly fault-tolerant — if one link fails, traffic routes around it. Disadvantage: expensive (many cables/ports), complex to manage.
• Ring Topology: Devices are connected in a closed loop. Data travels in one direction (or both in dual ring). Advantages: equal access, predictable performance. Disadvantage: a single break can disrupt the entire network (unless dual ring).

• World Wide Web (WWW): An information system on the Internet that allows documents to be connected to other documents by hypertext links.
• Web Browser & Client: The application (e.g., Chrome) used to request and render resources.
• Web Server: A computer hosting website files and responding to requests.
• HTML: The standard markup language for documents designed to be displayed in a web browser.
• URL: Uniform Resource Locator, the address of a given unique resource on the web.
• HTTP (Hypertext Transfer Protocol): The protocol over which web traffic runs. It defines how messages are formatted and transmitted.
• HTTPS (HTTP Secure): The secure version of HTTP. It uses SSL/TLS to encrypt the data transferred to protect against eavesdropping and tampering.

<form>
  <!-- Name -->
  <label for="name">Name:</label>
  <input type="text" id="name" name="name" required>

  <!-- Age -->
  <label for="age">Age:</label>
  <input type="number" id="age" name="age" required>

  <!-- Gender -->
  <label>Gender:</label>
  <input type="radio" id="male" name="gender" value="male">
  <label for="male">Male</label>
  <input type="radio" id="female" name="gender" value="female">
  <label for="female">Female</label>

  <!-- Submit -->
  <input type="submit" value="Submit">
</form>

<button onclick="showAlert()">Show Date & Time</button>

<script>
  function showAlert() {
    const currentDateTime = new Date().toLocaleString();
    alert("Current Date and Time: " + currentDateTime);
  }
</script>

<!DOCTYPE html>
<html>
<head>
  <title>BookNook Online Bookstore</title>
  <style>
    body { font-family: sans-serif; background-color: #f4f4f9; padding: 20px; }
    header { background-color: #2c3e50; color: white; padding: 15px; text-align: center; }
    ul { list-style-type: square; color: #333; margin-top: 20px; }
    li { padding: 5px 0; }
    .container { max-width: 800px; margin: auto; background: white; padding: 20px; border-radius: 8px; }
  </style>
</head>
<body>
  <div class="container">
    <header>
      <h1>Welcome to BookNook</h1>
    </header>
    <h2>Book Categories</h2>
    <ul>
      <li>Science Fiction & Fantasy</li>
      <li>Mystery & Thriller</li>
      <li>Biography & Autobiography</li>
      <li>Computers & Technology</li>
    </ul>
  </div>
</body>
</html>

p {
  color: darkgreen;
  font-size: 16px;
  line-height: 1.5;
}