BSc CSIT (TU) Science Introduction to Information Technology (BSc CSIT, CSC109) Question Paper 2079 Nepal

Functional Components of a Computer System

A computer system is an electronic device that accepts data, processes it according to stored instructions, and produces meaningful information. Its functional organization (the von Neumann model) consists of the following units:

Block Diagram (described in words)

        +----------------------------+
        |        CPU                 |
  Input |  +---------+  +---------+   | Output
  ----->|  |  ALU    |  | Control |   |----->
 Device |  +---------+  |  Unit   |   | Device
        |       ^       +----+----+   |
        |       |            |        |
        +-------|------------|--------+
                v            v
        +----------------------------+
        |     Memory (Main Memory)   |
        +----------------------------+

Arrows show flow of data (solid) and control signals between Input → CPU ↔ Memory → Output.

1. Input Unit

Accepts data and instructions from the outside world, converts them into binary (machine-readable) form, and supplies them to the memory/CPU. Examples: keyboard, mouse, scanner.

2. Central Processing Unit (CPU)

The “brain” of the computer that performs processing. It has two main parts:

• Arithmetic and Logic Unit (ALU): Performs arithmetic operations ($+, -, \times, \div$) and logical/comparison operations (AND, OR, NOT, $<, >, =$).
• Control Unit (CU): Directs and coordinates all operations by fetching, decoding and executing instructions and generating timing/control signals. It does not process data itself but tells other units what to do.
• Registers: Small, fast storage inside the CPU (e.g., Accumulator, PC, IR, MAR, MBR) that hold data and instructions during processing.

3. Memory Unit

Stores data, instructions and intermediate/final results.

• Primary memory (RAM, ROM): Directly accessible by the CPU, fast, holds currently executing programs.
• Secondary memory (hard disk, SSD): Permanent, larger but slower storage.

4. Output Unit

Converts the processed binary results back into human-readable form and presents them to the user. Examples: monitor, printer, speaker.

5. System Bus

A set of electrical pathways (Address bus, Data bus, Control bus) that interconnect the CPU, memory and I/O units to transfer data, addresses and control signals.

Working summary (IPO cycle): Input → Storage in memory → Processing by CPU (fetch–decode–execute) → Output, with the Control Unit coordinating each step.

Memory

Memory is the part of a computer that stores data, instructions and results either temporarily or permanently. It is organized as a set of cells, each with a unique address, that hold binary information for the CPU to access.

Types of Memory

Memory is broadly classified into Primary, Secondary, and Cache/Register memory.

1. Primary (Main) Memory

Directly accessible by the CPU; fast but limited in size.

• RAM (Random Access Memory): Volatile read/write memory that holds programs currently running. Loses contents when power is off.
  • SRAM (Static): fast, used in cache, no refresh needed.
  • DRAM (Dynamic): slower, denser, cheaper, needs periodic refresh; used as main memory.
• ROM (Read Only Memory): Non-volatile; stores permanent instructions like the bootstrap/BIOS. Types: PROM, EPROM, EEPROM.

2. Secondary (Auxiliary) Memory

Non-volatile, large-capacity, slower storage used for permanent data. Not directly accessed by the CPU. Examples: hard disk, SSD, optical disc (CD/DVD), magnetic tape, flash/pen drive.

3. Cache Memory and Registers

• Cache: Very fast SRAM placed between CPU and RAM to store frequently used data, reducing access time.
• Registers: Fastest, smallest storage inside the CPU itself.

Memory hierarchy (fastest/costliest → slowest/cheapest): Registers → Cache → RAM → Secondary storage.

Virtual Memory

Virtual memory is a memory-management technique that uses a portion of secondary storage (hard disk) as an extension of main memory (RAM). It gives a program the illusion of having a large, contiguous main memory larger than the physically available RAM.

• The OS divides programs into fixed-size blocks called pages and divides RAM into frames.
• Only the pages currently needed are kept in RAM; the rest reside on disk in a swap file / page file.
• When a referenced page is not in RAM, a page fault occurs and the OS swaps the required page in from disk (and may swap out an unused page).
• The mapping between virtual addresses and physical addresses is done by the MMU using a page table.

Advantage: programs larger than physical RAM can run, and more programs can run concurrently. Disadvantage: excessive swapping (thrashing) slows the system because disk is far slower than RAM.

World Wide Web (WWW)

The World Wide Web is an information system of interlinked hypertext documents (web pages) and other resources, identified by URLs and accessed over the Internet using the HTTP/HTTPS protocol. It was proposed by Tim Berners-Lee (1989). Web pages are written mainly in HTML and are viewed through web browsers.

WWW vs. Internet

In short: the Internet is the physical/logical network; the WWW is one application that uses that network.

Web Browser

A web browser is application software used to access, retrieve and display web pages from the WWW. It sends HTTP requests to web servers, receives HTML/CSS/JS, and renders it for the user. Examples: Google Chrome, Mozilla Firefox, Microsoft Edge, Safari. Features include tabs, bookmarks, history and address bar.

Search Engine

A search engine is a software system/website that lets users find information on the WWW using keywords. It uses crawlers/spiders to index web pages and ranks results by relevance. Examples: Google, Bing, Yahoo, DuckDuckGo.

URL (Uniform Resource Locator)

A URL is the unique address of a resource on the web. Structure:

https://www.example.com:443/path/page.html?id=10
  |        |              |     |             |
protocol  domain name    port  path        query string

• Protocol: how to access (http, https, ftp).
• Domain name: identifies the web server (resolved to an IP by DNS).
• Path: location of the specific resource on the server.

Example: https://www.tu.edu.np/notice/exam.html

Classification of Computers Based on Purpose

Based on the purpose for which they are designed, computers are classified into two types:

1. General-Purpose Computers

Designed to perform a wide variety of tasks by simply changing the program/software. They are flexible and not limited to one application.

• Can run many programs: word processing, accounting, games, browsing, etc.
• Lower processing speed for a specific task compared to special-purpose machines, but highly versatile.
• Examples: Personal computers (PCs), laptops, general servers.

2. Special-Purpose Computers

Designed and built to perform one specific task or a limited set of tasks. The program is usually fixed (embedded) into the hardware.

• Highly efficient, fast and accurate for the dedicated job, but cannot be used for other tasks.
• Examples: Computers in washing machines, ATMs, traffic-light controllers, weather-forecasting systems, aircraft autopilots, digital cameras.

Summary: General-purpose = flexible, multi-task; Special-purpose = dedicated, single-task, more efficient for that task.

Convert $(3FA)_{16}$ to Binary and Decimal

Hexadecimal → Binary

Replace each hex digit with its 4-bit binary equivalent:

Hexadecimal → Decimal

Using positional weights of base 16:

Results

Booting Process of a Computer

Booting is the process of starting up a computer and loading the operating system into RAM so the computer becomes ready to use. It begins when power is switched on and the CPU starts executing instructions from ROM (BIOS/UEFI).

Steps

1. Power On: Power supply sends voltage; the CPU is reset and begins executing the bootstrap code stored in ROM (BIOS/UEFI) at a fixed address.
2. POST (Power-On Self-Test): BIOS tests essential hardware—RAM, keyboard, display, disks. Errors are reported via beep codes/messages.
3. Locate Boot Device: BIOS reads the boot order and searches for a bootable device (hard disk/SSD/USB).
4. Load Boot Loader: The Master Boot Record (MBR) / boot loader (e.g., GRUB, Windows Boot Manager) is read from the boot sector into RAM.
5. Load Operating System: The boot loader loads the OS kernel from disk into RAM and transfers control to it.
6. Initialization: The OS loads drivers, system services and the user interface; the computer is ready for use.

Types

• Cold/Hard boot: Starting the computer from a completely powered-off state.
• Warm/Soft boot: Restarting an already-running computer (e.g., Ctrl+Alt+Del / Restart) without cutting power.

Impact vs. Non-Impact Printers

Summary: Impact printers work by hammering characters onto paper through a ribbon (good for multi-part forms but noisy and low quality), whereas non-impact printers form characters using ink jets, heat or laser without striking the paper (quieter, faster and higher quality).

Bus, Star and Ring Topologies

Topology is the physical or logical arrangement in which computers (nodes) are connected in a network.

1. Bus Topology

All nodes are connected to a single common cable called the backbone/bus, terminated at both ends.

• Data is broadcast along the bus; the intended node accepts it.
• Advantages: simple, cheap, uses least cable.
• Disadvantages: a fault in the backbone brings down the whole network; performance drops as nodes increase; difficult fault isolation.

2. Star Topology

All nodes are connected to a central device (hub/switch); communication passes through it.

• Advantages: easy to install/manage; failure of one node/cable does not affect others; easy fault detection.
• Disadvantages: if the central hub fails, the entire network goes down; needs more cable than bus.

3. Ring Topology

Each node is connected to exactly two neighbors forming a closed loop; data travels in one direction (often using a token).

• Advantages: orderly, no collisions (token passing); performs well under heavy load.
• Disadvantages: failure of one node/link can break the whole ring; adding/removing nodes disrupts the network.

Diagram (in words): Bus = nodes hanging off one straight line; Star = nodes radiating from a central hub; Ring = nodes joined in a circle.

Advantages and Disadvantages of Computer Networks

A computer network is a collection of interconnected computers that can share data and resources.

Advantages

1. Resource sharing: Hardware (printers, scanners) and software can be shared among many users, reducing cost.
2. Data/file sharing: Files and information can be quickly exchanged between connected computers.
3. Communication: Enables email, chat, video conferencing and instant messaging.
4. Centralized data and security management: Data can be stored and backed up centrally with controlled access.
5. Cost reduction: One resource (e.g., a single internet connection or printer) serves many users.
6. Reliability/scalability: Workload can be distributed; more nodes can be added easily.

Disadvantages

1. Security risks: Vulnerable to viruses, hacking and unauthorized access.
2. Setup and maintenance cost: Requires investment in cabling, servers and skilled administrators.
3. Dependency: If the server or main link fails, the whole network may stop working.
4. Loss of privacy: Shared data can be intercepted or misused.
5. Need for management: Requires a network administrator to manage and troubleshoot.
6. Spread of malware: Infections can spread quickly across connected machines.

SQL (Structured Query Language)

SQL is a standard programming language used to create, manage, query and manipulate data in a relational database. It allows users to define database structures, insert and update records, and retrieve information using simple English-like statements. It is supported by RDBMS such as MySQL, Oracle, SQL Server and PostgreSQL.

Main SQL Commands (by category)

1. DDL (Data Definition Language) – defines/modifies database structure:

• CREATE – create a database/table
• ALTER – modify table structure
• DROP – delete a table/database
• TRUNCATE – remove all rows from a table

2. DML (Data Manipulation Language) – manipulates data:

• INSERT – add new records
• UPDATE – modify existing records
• DELETE – remove records
• SELECT – retrieve/query data (sometimes called DQL)

3. DCL (Data Control Language) – controls access:

• GRANT – give privileges
• REVOKE – withdraw privileges

4. TCL (Transaction Control Language) – manages transactions:

• COMMIT, ROLLBACK, SAVEPOINT

Example:

SELECT name, marks FROM students WHERE marks > 40;

Elements of Multimedia

Multimedia is the integrated use of multiple media—text, graphics, audio, video and animation—to present information in an interactive way. Its five basic elements are:

1. Text

The most fundamental element; written characters, words and numbers used to convey information, titles, menus and content. Properties include font, size, style and color.

2. Graphics (Images)

Still pictures such as photographs, drawings, charts and diagrams. Two types: raster/bitmap (made of pixels, e.g., JPEG, PNG) and vector (made of mathematical lines/curves, scalable). Graphics make content visually appealing and explanatory.

3. Audio (Sound)

Includes music, speech/narration and sound effects. Common formats: MP3, WAV, MIDI. Enhances understanding and adds realism.

4. Video

A sequence of moving images, often combined with audio, that captures real-world or recorded action. Formats: MP4, AVI, MOV. Very effective for demonstrations and storytelling.

5. Animation

The rapid display of a sequence of images/frames to create the illusion of movement. Used for simulations, cartoons and visual effects (e.g., GIF, Flash, 3D animation).

(Interactivity is often included as a sixth element, allowing users to control navigation and flow.)

Short Notes on Cyber Crime

Cyber crime refers to any illegal or criminal activity carried out using computers, networks or the Internet, either by targeting computers/data or by using computers as a tool to commit a crime. It threatens the confidentiality, integrity and availability of information.

Common Types of Cyber Crime

• Hacking / unauthorized access: Breaking into computer systems to steal or alter data.
• Phishing: Tricking users via fake emails/websites to reveal passwords or bank details.
• Identity theft: Stealing someone’s personal information for fraud.
• Virus/malware attacks: Spreading malicious software to damage data or systems.
• Financial/online fraud: Credit-card fraud, fake online transactions.
• Cyber stalking / cyber bullying / defamation on social media.
• Software piracy and copyright infringement.
• Denial of Service (DoS) attacks that crash websites/servers.

Prevention

Use strong passwords, firewalls and antivirus software, keep systems updated, avoid suspicious links, encrypt sensitive data, and follow legal frameworks such as the Electronic Transactions Act, 2063 (Nepal) which penalizes cyber offences.

Conclusion: Cyber crime causes financial loss and breach of privacy, so awareness and proper security measures are essential.