Computer Fundamentals and Applications

An Operating System (OS) is system software that acts as an interface between the user and the computer hardware. It manages hardware resources and provides a platform on which application programs run. Examples are Windows, Linux, macOS and Android.

Functions of an operating system

1. Process management: Creates, schedules, and terminates processes; allocates the CPU to them (multitasking) and handles synchronization and deadlocks.
2. Memory management: Allocates and deallocates main memory to programs, keeps track of which parts are in use, and uses virtual memory when RAM is insufficient.
3. File management: Creates, deletes, copies, names, and organizes files and directories, and controls access to them.
4. Device management: Controls input/output devices through device drivers, and handles buffering, spooling, and device allocation.
5. Security and protection: Protects data and resources through user accounts, passwords, and permissions.
6. User interface: Provides a command-line interface (CLI) or graphical user interface (GUI) for the user to interact with the system.
7. Error detection and handling: Detects hardware and software errors and takes suitable action.
8. Resource allocation and accounting: Shares CPU, memory, and devices among users and keeps usage records.
9. Networking: Supports communication and resource sharing between computers.

An Operating System (OS) is system software that manages the computer hardware and software resources and provides an interface between the user and the hardware, e.g. Windows, Linux, macOS, Android.

Major functions of an operating system

1. Process management: Creates, schedules and terminates processes, allocates the CPU, and supports multitasking and synchronization.
2. Memory management: Allocates and frees main memory, tracks usage, and provides virtual memory.
3. File management: Organizes files and folders, and handles creation, deletion, copying, naming and access permissions.
4. Device management: Controls I/O devices through drivers, buffering and spooling.
5. Security and protection: Authentication by passwords and user accounts, and access control.
6. User interface: Offers CLI or GUI for interaction with the computer.
7. Error detection: Detects and reports hardware and software faults.
8. Resource allocation and job accounting: Shares resources fairly among users and programs and records their usage.
9. Networking and communication: Allows data exchange and resource sharing between computers.

Computer protocol

A protocol is a set of rules and conventions that govern how data is formatted, transmitted, received and checked between devices on a network. It lets different hardware and software communicate. Examples: TCP/IP, HTTP, FTP.

E-mail protocols

1. SMTP (Simple Mail Transfer Protocol)

   • Used to send e-mail from the client to the mail server, and from one mail server to another.
   • Works on TCP port 25 (587 for submission).
   • It is a push protocol: it cannot retrieve messages.

2. POP3 (Post Office Protocol version 3)

   • Used to receive e-mail. The client connects to the mail server, downloads messages to the local computer and, by default, deletes them from the server.
   • Works on TCP port 110 (995 with SSL).
   • Suitable for reading mail offline on one device.

IMAP (Internet Message Access Protocol) is the alternative to POP3. It keeps mail on the server and synchronizes it across many devices (port 143).

Utility software is system software that performs specific maintenance and support tasks to keep the computer healthy, secure and running well. It does not run the hardware as the operating system does, but it helps the OS and the user to analyze, configure, optimize and protect the system.

Justification with examples

• Antivirus software (Windows Defender, Avast, Kaspersky) detects and removes viruses and malware, which protects data and keeps the system stable.
• Disk defragmenter and disk cleanup rearrange scattered file fragments and delete temporary and junk files, which frees space and makes file access faster.
• Backup and restore utilities make copies of data so that files can be recovered after failure or accidental deletion.
• File compression tools (WinZip, WinRAR, 7-Zip) reduce file size to save disk space and make transfers faster.
• Disk partition and formatting tools prepare and organize storage drives.
• Task manager/system monitor shows running processes and resource use, and lets the user stop programs that hang.
• Firewall and encryption utilities control network access and protect data from unauthorized users.
• Uninstaller and driver updaters remove unwanted programs cleanly and keep drivers current.

Together these utilities prevent slowdowns, data loss and security problems, so they help the computer system function properly and smoothly.

A computer is an electronic device that accepts data as input, processes it under the control of a stored program according to given instructions, stores the results, and produces useful information as output.

Anatomy of a digital computer

            +-----------------------------------------+
            |        CENTRAL PROCESSING UNIT          |
 Input      |   +---------+       +-----------+       |     Output
 Unit  ---> |   | Control |<----->|    ALU    |       | ---> Unit
(keyboard,  |   |  Unit   |       +-----------+       |   (monitor,
 mouse)     |   +----+----+       | Registers |       |    printer)
            +--------|------------+-----------+-------+
                     |
               +-----v------+          +----------------+
               |  Primary   |<-------->| Secondary      |
               |  Memory    |          | Storage (HDD,  |
               | (RAM/ROM)  |          | SSD)           |
               +------------+          +----------------+

• Input unit: Accepts data and instructions from the user and converts them into binary form (keyboard, mouse, scanner).
• Central Processing Unit (CPU): The brain of the computer.
  • Control Unit (CU): Fetches instructions from memory, decodes them, and directs and coordinates all other units.
  • Arithmetic Logic Unit (ALU): Performs arithmetic operations (+, -, ×, ÷) and logical operations (AND, OR, NOT, comparisons).
  • Registers: Very fast small memory inside the CPU that holds the data and instructions currently being executed.
• Memory unit: Primary memory (RAM, ROM) holds the programs and data in use; secondary storage (hard disk, SSD, pen drive) stores data permanently.
• Output unit: Converts processed binary results into human-readable form (monitor, printer, speaker).

Data flows as input, then processing (CPU with memory), then output, with results optionally saved to storage.

A Database Management System (DBMS) is software that allows users to define, create, store, retrieve, update, and manage a database while providing security, integrity, and controlled shared access. Examples are MySQL, Oracle, SQL Server and MS Access.

Database models

1. Hierarchical model Data is organized as a tree of parent-child records; each child has exactly one parent (one-to-many).

• Merits: Simple, fast retrieval along known paths, good integrity between parent and child.
• Demerits: Cannot represent many-to-many relationships directly, rigid structure, and insertion/deletion is complex.

2. Network model Records are connected by links (graph structure); a child may have several parents (many-to-many).

• Merits: Flexible, represents complex relationships, efficient access.
• Demerits: Complex to design and maintain; changing structure is difficult; needs knowledge of the physical layout.

3. Relational model Data is stored in tables (relations) of rows and columns; relationships are expressed by keys (primary and foreign keys) and queried with SQL.

• Merits: Simple and easy to understand, data independence, powerful query language, flexible, and supports integrity constraints.
• Demerits: Can be slower than other models for very large or complex data, and requires more hardware and software resources.

4. Object-oriented model Data is stored as objects that combine attributes and methods, supporting classes and inheritance.

• Merits: Handles complex data (images, multimedia), reusability, and close fit with object-oriented languages.
• Demerits: No universal standard, higher complexity, and less mature than relational systems.

A topology is the physical or logical arrangement of the nodes and links in a network. The main LAN topologies are:

1. Bus topology All devices are connected to a single backbone cable, with terminators at both ends.

• Advantages: Cheap, easy to install, needs little cable.
• Disadvantages: A break in the main cable stops the whole network; performance falls with more nodes; difficult to troubleshoot.

2. Star topology All devices are connected to a central hub or switch.

• Advantages: Easy to install and extend; failure of one cable or node does not affect others; easy fault detection.
• Disadvantages: The central device is a single point of failure; needs more cable and is costlier.

3. Ring topology Each device is connected to exactly two neighbours, forming a closed loop; data travels in one direction (often with a token).

• Advantages: Orderly access with no collisions; performs well under heavy load.
• Disadvantages: A failure of one node or cable can break the ring; adding or removing nodes disrupts the network; troubleshooting is difficult.

4. Mesh topology Every device is connected to every other device (full mesh uses $n(n-1)/2$ links).

• Advantages: Very reliable with multiple paths; no traffic problem; secure.
• Disadvantages: Very expensive; complex installation and many cables.

5. Tree (hybrid) topology Star networks are joined to a bus backbone in a hierarchy.

• Advantages: Scalable; easy to manage by segments; fault isolation.
• Disadvantages: Failure of the backbone breaks the network; cabling and maintenance are complex.

The World Wide Web (WWW) is a global system of interlinked hypertext documents and multimedia resources (web pages) stored on web servers and accessed over the Internet using a browser and the HTTP protocol. Each resource is identified by a URL.

Internet, intranet and extranet

Contemporary technologies are the modern, recently developed technologies that are changing the way people live, work and do business, such as Artificial Intelligence, Internet of Things, Cloud Computing, Blockchain, Big Data, and Virtual/Augmented Reality.

1. Artificial Intelligence (AI) AI enables machines to simulate human intelligence: learning, reasoning, and decision making.

• Roles: Chatbots and virtual assistants for customer service; medical image diagnosis; fraud detection in banking; recommendation systems (e-commerce, video streaming); automation of repetitive tasks; self-driving vehicles.

2. Cloud Computing Delivery of computing services (storage, servers, databases, software) over the Internet on a pay-as-you-use basis (IaaS, PaaS, SaaS).

• Roles: Reduces the cost of buying and maintaining hardware; allows access to data from anywhere; scalable resources on demand; backup and disaster recovery; supports online collaboration (Google Drive, Office 365).

(a) Create the sub directories theory and practical inside d:\exam\:

d:
cd \exam
mkdir theory practical

(b) Create marks.txt inside theory with the given content:

echo Theory marks in CFA > d:\exam\theory\marks.txt

(c) Rename the file:

ren d:\exam\theory\marks.txt CFAmarks.txt

(d) Hide the file:

attrib +h d:\exam\theory\CFAmarks.txt

(e) Search all files with the .pdf extension (in the current drive, including subdirectories):

dir \*.pdf /s

(a) Let the headings be in row 1: A = Name, B = Eng., C = Nep., D = Eco., E = Sociology, F = Computer, G = Total, H = Percentage, I = Result, J = Division. Data for Gautam is in row 2 (formulas are filled down to row 6).

1. Total (in G2):

=SUM(B2:F2)

2. Percentage (in H2), total marks being $5 \times 100 = 500$:

=G2/500*100

(equivalently =G2/5).

3. Result (in I2), pass requires at least 35 in every subject:

=IF(MIN(B2:F2)>=35,"PASS","FAIL")

4. Division (in J2):

=IF(H2>=60,"First",IF(H2>=45,"Second",IF(H2>=35,"Third","xxx")))

Results obtained: Gautam 331 (66.2%), First; Saru 325 (65%), First; Binod 331 (66.2%), First; Ritu 325 (65%), First; Kabindra 297 (59.4%), Second by percentage, but the result is FAIL because he scored 34 in Nepali.

(b) Font control tools in a word processor

The Font group (Home tab or Font dialog box) controls how characters look:

• Font face/name: Choose the typeface, e.g. Calibri, Times New Roman.
• Font size: Increase or decrease character size in points; grow/shrink buttons.
• Font style: Bold, italic and underline (single, double, dotted etc.).
• Font color: Changes the text color.
• Text highlight color: Highlights text like a marker pen.
• Strikethrough and double strikethrough: Draws a line through text.
• Subscript and superscript: Lowers or raises characters (H₂O, x²).
• Change case: Sentence case, lowercase, UPPERCASE, capitalize each word, toggle case.
• Text effects and typography: Shadow, outline, glow, reflection, small caps, all caps, character spacing.
• Clear all formatting: Removes applied formatting.
• Format Painter: Copies the formatting of one text to another.

(a) Computer peripherals are external hardware devices connected to the computer to give input, receive output or store data, e.g. keyboard, mouse, monitor, printer, scanner.

Impact vs non-impact printers

(b) A presentation is a collection of slides containing text, images, charts, audio and video, used to communicate ideas to an audience (e.g. MS PowerPoint, Google Slides).

Features of a good presentation package

• Ready-made templates, themes and slide layouts.
• Slide Master for consistent design across slides.
• Insertion of text, tables, pictures, charts, SmartArt, audio and video.
• Animation and slide transition effects.
• Multiple views (Normal, Slide Sorter, Slide Show, Notes).
• Speaker notes and handouts.
• Hyperlinks and action buttons for navigation.
• Slide show controls such as timing, rehearsal and presenter view.
• Saving/exporting in various formats (PPTX, PDF, video) and printing.
• Spell check, collaboration, and sharing.

CMYK color model

CMYK is a subtractive color model used in printing. It stands for Cyan, Magenta, Yellow and Key (Black). Colors are created by absorbing (subtracting) light from white paper using the four ink colors, each in the range 0-100%. Black (K) is added because mixing C, M and Y gives only a muddy dark brown and black text is cheaper with a single ink.

Basic tools in Photoshop

• Move tool: Moves selections or layers.
• Selection tools: Marquee (rectangle, ellipse), Lasso (free, polygonal, magnetic), Quick Selection and Magic Wand select regions of an image.
• Crop tool: Trims the image to a chosen area.
• Eyedropper: Picks a color from the image.
• Brush and Pencil: Paint on the canvas.
• Eraser: Removes pixels.
• Clone Stamp and Healing Brush: Copy or repair parts of an image (remove blemishes, objects).
• Gradient and Paint Bucket: Fill areas with gradients or solid color.
• Type tool: Adds text.
• Pen and Shape tools: Create paths and vector shapes.
• Zoom and Hand tools: Zoom and pan the view.
• Blur, Sharpen, Dodge, Burn: Retouching tools.

Transforms (Edit > Transform / Ctrl+T)

• Scale: Resize the object (hold Shift to keep proportion).
• Rotate: Turn by an angle (90° or free).
• Skew: Slant horizontally or vertically.
• Distort: Move corners freely.
• Perspective: Give a 3D depth effect.
• Warp: Bend the object into a custom shape.
• Flip horizontal/vertical: Mirror the object.

A computer virus is a malicious program that attaches itself to legitimate files or programs, replicates itself when the host is executed, and spreads from one computer to another, often damaging data, software or system performance.

Symptoms of a computer virus

• The computer runs unusually slowly or hangs and crashes frequently.
• Programs take a long time to load or fail to start.
• Unexpected pop-ups, messages or advertisements appear.
• Files or folders go missing, become corrupted, or file sizes change unexpectedly.
• Disk space or memory decreases without a reason.
• The system restarts or shuts down on its own.
• Antivirus or Task Manager is disabled or cannot be opened.
• The hard disk shows excessive activity and the network is unusually busy.
• The browser home page changes or unknown toolbars and programs appear.
• Unusual error messages or strange files with odd extensions appear.

A database is an organized collection of related data stored so that it can be easily accessed, managed and updated, normally through a DBMS. A file-based system stores data in separate files for each application.

Advantages of a database over a file-based system

1. Reduced data redundancy: Data is stored once rather than being duplicated in many files.
2. Data consistency: With less duplication, the same data is the same everywhere.
3. Data integrity: Constraints (keys, validation rules) keep data accurate.
4. Data independence: Programs are not affected by changes in the storage structure.
5. Data sharing: Many users and applications share the same data at the same time.
6. Security: Access rights restrict users to the data they are authorized for.
7. Backup and recovery: The DBMS provides automatic backup and recovery.
8. Easy querying: Query languages like SQL give fast and flexible retrieval.
9. Concurrent access control: Transactions and locking avoid conflicts.
10. Standards and lower maintenance cost are easier to enforce.

A proxy server is an intermediate server that sits between client computers and the Internet. A client sends its request to the proxy, which forwards it to the destination server, receives the response, and returns it to the client, hiding the client's real IP address.

Benefits of using a proxy server in an organization

1. Content filtering and access control: Blocks unwanted or harmful websites and enforces browsing policy.
2. Caching: Stores frequently visited pages locally, so they load faster and bandwidth is saved.
3. Security: Hides internal IP addresses, filters malicious content and acts as a protection layer along with the firewall.
4. Privacy and anonymity: The external servers see only the proxy's address.
5. Monitoring and logging: Tracks Internet usage of employees.
6. Bandwidth control: Limits or prioritizes the Internet use of users.
7. Single point of Internet access: Many internal computers can share one Internet connection.

E-commerce (electronic commerce) is the buying and selling of goods and services, and the transfer of money and data, over the Internet or other electronic networks. Examples are Daraz, Amazon and eSewa/Khalti-based online payments.

Benefits to customers

1. Convenience: Shop from home at any time (24/7) without travelling.
2. Wide choice: Products from many sellers, local and global, are available.
3. Price comparison: Easy to compare prices and features and find the best deal.
4. Time and cost saving: No travelling cost and no queues.
5. Discounts and offers: Lower prices through online deals and coupons.
6. Customer reviews: Ratings and reviews help make informed choices.
7. Easy payment options: Cards, mobile wallets, and cash on delivery.
8. Home delivery and easy order tracking.

The structure is taken as: E:\ROOT containing the directories dir_1 (with file_1.txt and file_2.txt) and dir_3 (with dir_2.txt and file_2.txt).

(a) Create the directories and files:

E:
mkdir ROOT
cd ROOT
mkdir dir_1 dir_3
echo. > dir_1\file_1.txt
echo. > dir_1\file_2.txt
echo. > dir_3\dir_2.txt
echo. > dir_3\file_2.txt

(b) Move all text files into dir_3 (/Y overwrites the duplicate file_2.txt without a prompt):

move /Y E:\ROOT\dir_1\*.txt E:\ROOT\dir_3\

(c) Delete the dir_1 directory with its content:

rmdir /s /q E:\ROOT\dir_1

(d) Hide the root directory:

attrib +h E:\ROOT

A word processor is application software used to create, edit, format, store, and print text documents such as letters, reports, and books. Examples are MS Word, Google Docs and LibreOffice Writer.

Major functions in the Home tab of MS Word

The Home tab has five main groups.

1. Clipboard group

• Paste: Inserts cut or copied content (with paste options such as keep source formatting or text only).
• Cut and Copy: Move or duplicate selected content.
• Format Painter: Copies formatting from one place to another.

2. Font group

• Font face and size, grow/shrink font.
• Bold, italic, underline, strikethrough.
• Subscript and superscript.
• Change case.
• Text effects, text highlight color, and font color.
• Clear all formatting.

3. Paragraph group

• Bullets, numbering and multilevel lists.
• Increase and decrease indent.
• Alignment: left, center, right, justify.
• Line and paragraph spacing.
• Shading and borders.
• Sort and show/hide paragraph marks.

4. Styles group

• Applies predefined styles such as Normal, Heading 1, Heading 2, Title, to give a uniform look and enable table of contents.

5. Editing group

• Find: Searches text in the document.
• Replace: Replaces text with other text.
• Select: Selects all text or objects.

(a) Animation is the process of creating the illusion of motion by displaying a sequence of images or by applying movement effects to objects. In PowerPoint, animation applies entry, emphasis, exit and motion path effects to text, pictures and shapes on a slide to make a presentation more attractive.

Advantages of Slide Master

• Consistency: One place to set the fonts, colors, background and layout for all slides.
• Time saving: A change in the master updates all slides at once.
• Common elements: A logo, footer, date and slide number can be placed on all slides once.
• Custom layouts: Create and reuse new layouts.
• Professional look: Maintains a uniform theme and branding.
• Easy maintenance of large presentations.

(b) Block diagram of a computer

 Input Unit --> [ CPU: Control Unit + ALU + Registers ] --> Output Unit
                        ^        |
                        |        v
                 Primary Memory <--> Secondary Storage

Components

• Input unit: Takes data and instructions from the user and converts them to binary (keyboard, mouse, scanner).
• Control Unit: Fetches, decodes and executes instructions, and controls and coordinates all other units.
• Arithmetic Logic Unit: Carries out arithmetic and logical operations.
• Registers: Fast storage in the CPU for the data being processed.
• Primary memory: RAM holds data and programs in use; ROM holds the start-up instructions.
• Secondary storage: Permanent storage of data and programs (hard disk, SSD).
• Output unit: Presents the processed result in human-readable form (monitor, printer, speaker).

(b) Dot-matrix

A dot-matrix printer is an impact printer: its pins strike an inked ribbon against the paper. Inkjet, laser and thermal printers print without physical impact.

(a) Anti-virus

Utility software performs maintenance tasks such as protecting, cleaning and managing the system. An anti-virus detects and removes malware, whereas an operating system is system software, a language translator is development software, and a word processor is application software.

(c) Windows 7

Windows 7 is a desktop (client) operating system. Unix, Linux and Windows Server are designed as network operating systems that manage users, resources and services on a network.

(d) Primary Key

A primary key uniquely identifies each row of a table and cannot be null or duplicated. A candidate key is only a possible choice for the primary key, a foreign key links to another table, and a composite key is a key made of more than one column.

(b) Transport Layer

TCP (Transmission Control Protocol) works at the Transport layer (layer 4) of the OSI model and provides reliable, connection-oriented end-to-end delivery.

(d) HTTP

HTTP is a protocol, not a web server. Apache, IIS (Internet Information Services) and GWS (Google Web Server) are web server software.

(c) Bit Coin

Bitcoin is a decentralized digital (crypto) currency that uses cryptography and blockchain to secure transactions. Credit cards, PayPal and Mastercard are conventional payment instruments or services, not crypto-currencies.

(b) shutdown /s

The /s switch shuts down the computer normally. /r restarts it, /h hibernates it, and /f forces running applications to close.

(c) Calibri

Calibri (11 pt) has been the default body font since Word 2007 and remained so in Word 2016. Word 2016 uses Calibri for body text and Calibri Light for headings.

(a) F1

F1 opens the Help pane in MS PowerPoint. F5 starts the slide show from the beginning, F6 moves between panes, and F11 is not used for help.

A database administrator (DBA) is the person (or team) responsible for the design, installation, security, performance, availability and maintenance of an organization's databases and the DBMS software that manages them.

Major roles and responsibilities of a DBA

• Database design and definition: Works with analysts to create the logical and physical schema, decide tables, keys, indexes and constraints.
• Installation and configuration: Installs and upgrades the DBMS software, applies patches and tunes system parameters.
• Security and access control: Creates user accounts, grants and revokes privileges, enforces authentication and encryption, and audits access.
• Backup and recovery: Plans regular backups, tests restore procedures, and recovers the database after failures such as disk crash or power loss.
• Performance tuning: Monitors queries, builds indexes, optimizes storage and memory use so that response time stays acceptable.
• Data integrity and consistency: Defines integrity rules, controls concurrent access and resolves deadlocks.
• Capacity planning and storage management: Estimates growth and allocates disk space.
• User support and training: Helps developers and end users with queries and documents standards and procedures.

Ergonomic keyboard

An ergonomic keyboard is a keyboard designed to reduce strain on the wrists, hands and arms and to keep a natural posture during long typing sessions. Typical features are a split or curved key layout, a tilted or tented design, a built-in palm (wrist) rest and a reduced reach to the keys. It helps prevent repetitive strain injury and carpal tunnel syndrome.

Working mechanism of a keyboard

1. Key press: Each key sits above a switch (membrane, mechanical or scissor type). Pressing a key closes a circuit at that position in a matrix of rows and columns.
2. Scanning: A microcontroller inside the keyboard continuously scans the matrix. When a circuit is closed, it identifies the row and column and so finds which key is pressed.
3. Scan code: The controller converts the key position into a unique scan code (a make code when the key is pressed and a break code when it is released).
4. Transmission: The scan code is sent to the computer through a cable (PS/2 or USB) or wirelessly (Bluetooth or radio).
5. Processing: The keyboard driver and the operating system translate the scan code into a character, taking Shift, Ctrl, Caps Lock and the current language layout into account. The character is placed in the keyboard buffer and passed to the active program, which displays it on screen.

Computers are classified by size, speed, storage and processing power into four main types.

1. Supercomputers The fastest and most powerful computers, with thousands of processors working in parallel and speeds measured in petaflops. They are very expensive and are used for weather forecasting, nuclear simulation, space research and genome analysis. Examples: Fugaku, Summit, Cray.

2. Mainframe computers Large, powerful computers that serve hundreds or thousands of users at the same time through terminals. They have large memory and storage, high reliability and strong security. They are used by banks, airlines, insurance companies and governments for bulk transaction processing. Example: IBM zSeries.

3. Minicomputers (mid-range computers) Smaller and cheaper than mainframes but more powerful than PCs. They support tens to hundreds of users and are used in small organizations, laboratories and manufacturing control. Examples: PDP-11, VAX, IBM AS/400.

4. Microcomputers (personal computers) Computers built around a microprocessor, meant for one user. They include desktops, laptops, tablets, smartphones and workstations. They are cheap, small and used at home, offices and schools.

In decreasing order of power: supercomputer, mainframe, minicomputer, microcomputer.

DBMS

A Database Management System (DBMS) is software that lets users define, create, store, retrieve, update and control access to a database. It provides data independence, reduced redundancy, integrity, security, concurrency control and backup/recovery. Examples: MySQL, Oracle, SQL Server, PostgreSQL.

Relational database model

Proposed by E. F. Codd in 1970, the relational model organizes data into relations (tables).

• A table consists of rows (tuples/records) and columns (attributes/fields).
• Each column has a domain (set of allowed values) and each row is unique.
• A primary key uniquely identifies each row; a foreign key is an attribute that refers to the primary key of another table and so links the tables.
• Data is manipulated by relational operations (select, project, join), commonly through SQL.

Example

STUDENT

COURSE

STUDENT (RollNo, Name, CourseID)  >-----  COURSE (CourseID, CourseName)
                          foreign key ---> primary key

Many students can belong to one course (one-to-many), and the link is made by the common attribute CourseID. This model is simple, flexible and the most widely used.

Specification of a personal computer (desktop for study, programming and office work)

Total estimate: about Rs 90,000 (the sum of the items above is Rs 87,500 plus the OS cost).

Reasons: the SSD gives fast booting, 16 GB RAM allows programming tools and multitasking, and the multi-core processor runs compilers and office software smoothly. The UPS protects against power cuts.

DOS commands are typed at the command prompt. Five common ones:

1. DIR lists the files and folders in the current directory. Example: DIR C:\Data shows the contents of C:\Data. DIR *.txt shows only text files.
2. CD (change directory) moves to another folder. Example: CD \Data\Notes goes to the Notes folder, CD .. goes one level up.
3. COPY copies one or more files. Example: COPY report.txt D:\Backup copies report.txt to D:\Backup.
4. DEL deletes files. Example: DEL old.txt deletes old.txt, and DEL *.tmp deletes all .tmp files.
5. MD (or MKDIR) creates a new directory. Example: MD Project creates a folder named Project.

Other useful commands are CLS (clear screen), REN (rename), TYPE (display a file) and DATE/TIME.

(a) Mail merge and the Review tab

Mail merge is a Word feature that produces many personalized documents (letters, labels, envelopes, certificates) from one main document and a data source. The main document holds the fixed text and merge fields such as «Name» and «Address». The data source (an Excel sheet, Access table or contact list) holds the variable data. When merged, Word creates one copy per record with the fields replaced by that record's data.

Major functions in the Review tab

• Proofing: Spelling and Grammar check, Thesaurus and Word Count.
• Accessibility: Check Accessibility to find problems for users with disabilities.
• Language: Translate text and set the proofing language.
• Comments: New Comment, Delete, Previous/Next to add notes for reviewers.
• Tracking: Track Changes records insertions and deletions; Show Markup chooses what to display; Reviewing Pane lists the changes.
• Changes: Accept or Reject a change, and move to the next or previous change.
• Compare: Compares two versions of a document, or combines the work of several authors.
• Protect: Restrict Editing and Block Authors control who can edit.

(b) Photoshop and MRP-sized photograph

Adobe Photoshop is a raster graphics editing program used to edit, retouch, composite and create images and artwork using layers, selections, filters and colour tools.

Steps to create a Machine Readable Passport (MRP) photograph in JPEG (typically 35 mm x 45 mm, white background, 300 dpi):

1. Open the photo with File > Open.
2. Choose the Crop tool and set Width 35 mm, Height 45 mm and Resolution 300 pixels/inch; crop so the face fills about 70 to 80 percent of the frame, centred.
3. Remove the background with the Quick Selection or Select Subject tool, then fill it with white on a new layer.
4. Adjust brightness, contrast and colour (Image > Adjustments) and retouch blemishes.
5. Check the size in Image > Image Size (35 mm x 45 mm at 300 dpi, about 413 x 531 pixels).
6. Save using File > Save As, select JPEG format, set quality to high and click Save.

Computer network

A computer network is a group of two or more computers and other devices connected by wired or wireless media so that they can share data, files, hardware resources (printers) and internet access. Types include PAN, LAN, MAN and WAN.

OSI model

The Open Systems Interconnection (OSI) reference model, developed by ISO, divides network communication into seven layers. Each layer provides services to the layer above and uses the services of the layer below. Data is encapsulated with a header as it moves down the sender's stack and is de-encapsulated at the receiver.

Memory aid (top to bottom): All People Seem To Need Data Processing.

Advantages: it standardizes network design, lets products from different vendors work together, simplifies troubleshooting by isolating problems to a layer, and lets layers change independently.

Diligence

A computer is free from tiredness, boredom and lack of concentration. It can work for hours continuously with the same speed and accuracy, whereas a human gets tired. For example, it can process millions of payroll records or run a calculation repeatedly without any decline in accuracy.

Versatility

A computer can perform many different kinds of tasks, simply by changing the program. The same machine can prepare documents, do calculations, play music and video, run simulations, manage databases, browse the internet and control other devices. It is used in education, banking, health, entertainment, engineering and many other fields.

Together, diligence and versatility make the computer reliable and applicable to almost any job.

Computer software

Computer software is a set of programs, instructions and related data that tells the hardware what to do and how to do it. It has no physical form and is stored in the computer's memory or on storage devices.

Types of software

1. System software: Controls and manages the hardware and provides a platform for other software.

   • Operating system: Windows, Linux, macOS, Android.
   • Utility programs: antivirus, disk cleanup, backup, file compression.
   • Device drivers: let the OS communicate with printers, graphics cards.
   • Language translators: compiler, interpreter, assembler.

2. Application software: Helps users perform specific tasks.

   • General-purpose: word processor, spreadsheet, web browser, presentation software.
   • Specific-purpose: accounting software, hospital management, payroll, airline reservation.
   • Customized (tailor-made) software developed for one organization.

3. Programming software: Tools such as editors, compilers, debuggers and IDEs used to write other programs.

Based on availability, software can also be proprietary, open-source, freeware or shareware.

A user interface is the means through which a user communicates with the computer. The operating system (OS) acts as this interface between the user and the hardware: the user does not need to know hardware details such as disk sectors or memory addresses; they give commands to the OS, which carries them out on the hardware and returns the result.

Types of OS interface

• Command-line interface (CLI): The user types commands, such as dir or copy in MS-DOS or a Linux shell.
• Graphical user interface (GUI): The user works with windows, icons, menus and a pointer, as in Windows or macOS.

Example

When a user double-clicks a file icon to open a document in Windows, the OS interprets the click, locates the file on the disk, loads it into memory, starts the word processor, and displays the document on the monitor. When the user prints it, the OS sends it to the printer driver. The user only used icons and menus and never dealt with the hardware directly.

Hence the statement is justified: the operating system provides a convenient, easy-to-use interface between the user (and application programs) and the computer hardware.

Data warehouse

A data warehouse is a large, centralized repository of integrated, historical data collected from many operational sources (databases, files, external systems) and organized for query, reporting and analysis rather than day-to-day transactions. Its data is subject-oriented, integrated, time-variant and non-volatile. It supports decision making and data mining.

Advantages

• Provides a single, consolidated view of enterprise data.
• Improves decision making through trend, forecasting and business intelligence analysis.
• Improves data quality and consistency by cleaning and standardizing data.
• Stores historical data over long periods.
• Queries run fast and do not slow the operational systems.
• Increases return on investment and helps find new opportunities.

Disadvantages

• Building and maintaining a warehouse is expensive and time consuming.
• Extracting, transforming and loading (ETL) data is complex.
• Data can become outdated because it is loaded periodically, not in real time.
• Requires large storage and skilled staff.
• Combining data raises security and privacy concerns.
• Integrating incompatible source systems is difficult.

Computer network

A computer network is a collection of interconnected computers and devices (hosts, printers, switches, routers) linked through wired or wireless media so that they can exchange data and share resources. Examples are a LAN in an office, a WAN across cities and the Internet.

Why organizations need a computer network

• Resource sharing: Printers, scanners, storage and software are shared, reducing cost.
• Data sharing and centralization: Files and databases are stored on a server and accessed by all authorized employees, keeping data consistent.
• Fast communication: E-mail, chat, video conferencing and VoIP connect staff and branches quickly.
• Cost saving: Licences, hardware and internet connections are shared.
• Centralized backup and security: Data is backed up in one place and access is controlled by user accounts.
• Remote access and e-commerce: Employees can work from anywhere, and customers can use online services.
• Reliability and scalability: Work can continue on other machines if one fails, and new users can be added easily.

Hypermedia

Hypermedia is an extension of hypertext in which text, graphics, images, audio, video and animation are linked together by hyperlinks, so users can move non-linearly from one piece of information to another by clicking. The World Wide Web is the best-known example of hypermedia, and it is also used in multimedia encyclopedias and e-learning courses.

Applications of augmented reality (AR)

AR overlays computer-generated images, sound or information onto the real-world view, usually through a smartphone, tablet or smart glasses.

• Education: 3D models and interactive lessons, such as the human body or planets.
• Healthcare: Surgeons see scans overlaid on the patient; medical training.
• Gaming and entertainment: Pokemon Go, filters in social media apps.
• Retail and e-commerce: Trying on clothes, glasses or placing furniture virtually in a room.
• Navigation: Live directions overlaid on the road.
• Industry and maintenance: Step-by-step repair guidance, design visualization.
• Military and training: Simulation and heads-up displays.
• Real estate and tourism: Virtual tours and information on landmarks.

(a) Excel formulas

Assume column A is SN, B is Name, C is monthly Salary, D is Service Tax, E is Income Tax, F is Total and G is Net Salary, with data in rows 2 to 5. The yearly salary is C2*12, and the tax rates are applied to the salary.

Service Tax (D2):

$\texttt{=IF(C2*12>150000, 5\%, 1\%)*C2}$

Income Tax (E2):

$\texttt{=IF(C2*12<=100000, 0, IF(C2*12<200000, 10\%, 15\%))*C2}$

Total (F2): =D2+E2

Net Salary (G2): =C2-F2

Fill these formulas down to row 5. Results:

(b) DOS commands

• ATTRIB displays or changes file attributes (R read-only, A archive, S system, H hidden). Example: ATTRIB +R +H data.txt makes data.txt read-only and hidden; ATTRIB -H data.txt removes the hidden attribute.
• XCOPY copies files and whole directory trees, with more options than COPY. Example: XCOPY C:\Project D:\Backup /S /E copies all files and subfolders, including empty ones.
• MKDIR (MD) creates a directory. Example: MKDIR C:\College\BCA creates folder BCA inside College.
• MOVE moves files or folders to another location (and can rename them). Example: MOVE C:\a.txt D:\Docs moves a.txt to D:\Docs.
• DEL deletes one or more files. Example: DEL C:\Temp\*.tmp deletes all .tmp files in Temp.

(a) Major functions in the Layout tab of Word

• Page Setup: Margins (normal, narrow, custom), Orientation (portrait or landscape), Size (A4, Letter, legal), Columns (split text into columns), Breaks (page, section, column breaks), Line Numbers and Hyphenation.
• Paragraph: Indent left and right, and Spacing before and after paragraphs.
• Arrange: Position and Wrap Text for objects, Bring Forward, Send Backward, Selection Pane, Align, Group and Rotate for pictures and shapes.

(In older Word versions this tab is called Page Layout and also contains Themes and Page Background, such as Watermark, Page Color and Page Borders.)

(b) Layers in Photoshop

Use of a layer: A layer is like a transparent sheet stacked over others. Each layer holds a separate part of the image (picture, text, shape, adjustment), so one element can be moved, resized, edited, hidden or deleted without affecting the rest of the image. This gives non-destructive editing, lets different blend modes and opacity be applied and allows a composite image to be built.

Organizing layers

• Naming layers meaningfully (double-click the name).
• Colour coding layers for quick identification.
• Grouping related layers into folders (Layer > New > Group, or Ctrl+G).
• Reordering by dragging layers up or down in the Layers panel, since upper layers cover lower ones.
• Linking layers to move them together, and locking layers to protect them.
• Hiding layers with the eye icon, deleting unused layers and merging or flattening when finished (Layer > Merge Layers).
• Using adjustment layers and layer masks to keep edits non-destructive.

Hardcopy devices

Hardcopy devices produce output on a physical medium such as paper or film that can be held and kept. Printers, plotters and some scanners/copiers fall in this class. Printers are divided into impact printers (dot-matrix), which strike the paper, and non-impact printers (laser, ink-jet), which do not.

1. Dot-matrix printer

• The print head contains a column of small pins (9 or 24).
• The head moves across the paper. For each character, the controller fires selected pins by electromagnets.
• The pins strike an inked ribbon against the paper, leaving dots which together form the character or image.
• It can print multi-part carbon copies, is cheap to run but is slow, noisy and gives low print quality.

2. Ink-jet printer

• The print head has many tiny nozzles connected to ink cartridges (cyan, magenta, yellow, black).
• Ink drops are sprayed onto the paper, either by heating the ink to form a vapour bubble (thermal) or by a piezoelectric crystal that squeezes out a drop.
• The head moves across the paper while the paper feeds forward, forming the image dot by dot.
• Quiet, good colour and photo quality, but ink is costly and the output can smudge.

3. Laser printer

1. A rotating drum is given a uniform electrostatic charge.
2. A laser beam, controlled by the data, draws the image on the drum, discharging the lit areas.
3. Toner (powdered ink) sticks to the discharged image areas.
4. The drum rolls against the paper, which carries a stronger opposite charge, so the toner transfers to the paper.
5. The fuser heats and presses the paper so toner melts and bonds.
6. The drum is cleaned and recharged for the next page.

It is fast, quiet and gives high-quality text, with a lower cost per page for large volume.

Computer interface

A computer interface is the point or means of interaction between two components, such as the user and the computer, or the computer and a peripheral device. Types:

• User interface: command-line, graphical (GUI), menu-driven or touch interface.
• Hardware interface: ports and connectors such as USB, HDMI, Ethernet.
• Software interface: an API that lets programs communicate.

Essential features of a mainframe computer

• Very large processing power and memory: Handles huge volumes of data and thousands of transactions per second.
• Multi-user: Hundreds or thousands of users can access it at once through terminals.
• High reliability and availability: Built with redundant components; it runs continuously for years.
• Large storage and input/output capacity: Manages massive databases through many I/O channels.
• Strong security and data integrity.
• Multitasking, batch and transaction processing with a specialized operating system such as z/OS.
• Expensive and needs a controlled environment, but each user costs less.

They are used by banks, insurance companies, airlines and government agencies, for example the IBM zSeries.

Utility programs

Utility programs are system software that perform maintenance and supporting tasks to help manage, analyse, protect and optimize the computer. Common kinds are:

• Antivirus and anti-malware software
• Disk cleanup and disk defragmenter
• Backup and restore programs
• File compression tools (WinZip, WinRAR)
• File manager and search tools
• Disk partition and formatting tools
• Firewall and encryption tools
• Task manager and system monitoring tools

Example: Antivirus (e.g., Windows Defender)

An antivirus program scans files, downloads, e-mail attachments and memory for malicious software such as viruses, worms and trojans. It compares them with a database of known virus signatures and also detects suspicious behaviour. When it finds a threat it quarantines or deletes it. It runs in the background providing real-time protection and updates its definitions regularly, and so protects the data and performance of the computer.

An operating system (OS) is the resource manager of a computer. It allocates the limited hardware resources fairly and efficiently among the programs and users that need them.

Resources managed

• Processor (CPU) management: The scheduler decides which process runs and for how long, using algorithms such as round robin, so that the CPU is used well and many programs seem to run together.
• Memory management: Allocates RAM to processes, keeps track of free and used areas, protects one process from another and uses virtual memory when RAM is short.
• File and storage management: Organizes files and directories, allocates disk space and controls access permissions.
• Device (I/O) management: Controls peripherals through drivers, buffering and spooling.
• Security and accounting: Controls access to resources by user authentication.

Example

Suppose a user is typing in a word processor, listening to music and printing a document at the same time. The OS gives the CPU to each program in short time slices, assigns separate RAM areas to each so they do not overwrite one another, queues the print job through a spooler so the printer is not blocked, and reads the music file from the disk. If the memory becomes full, it moves idle data to the swap area on the disk. Thus all programs share the resources without conflict.

The databases of an organization are supervised by the Database Administrator (DBA). The DBA is a person (or a team) with central control over the data and the DBMS software, and is responsible for keeping the database available, consistent, secure and efficient.

Tasks and obligations of the DBA

1. Database design and definition: works with analysts and designers on the conceptual, logical and physical schema, and defines tables, keys, constraints and views.
2. Installation and configuration: installs, upgrades and patches the DBMS and tunes its parameters.
3. Security and access control: creates users and roles, grants or revokes privileges, and enforces authentication and authorization so that only permitted people see or change data.
4. Backup and recovery: plans regular backups, tests them, and restores the database after hardware failure, crashes or data loss.
5. Performance monitoring and tuning: watches query performance, creates indexes, optimizes queries and storage, and plans capacity.
6. Integrity and consistency: defines and enforces integrity constraints and controls concurrent access, so that data stays accurate.
7. Data dictionary and standards: maintains documentation (metadata), naming conventions and data standards.
8. User support and training: helps developers and end users, resolves problems and advises on proper use of the database.
9. Data migration and archiving: moves data between systems and archives old data.
10. Policy and compliance: applies the organization's data policies and legal rules on privacy and retention.

A computer network lets computers, printers and other devices in an office share resources and information, which reduces the money and effort spent on running the office (overhead).

Ways a network lowers overhead

• Shared hardware: one laser printer, scanner or plotter can serve all users instead of buying one for each desk.
• Shared software and licences: software can be installed on a server and used by many users under a network licence, and updates are done in one place.
• Shared data and files: documents are kept on a file server, so there are no duplicate copies and no need to carry disks or print papers to pass information around.
• Cheaper communication: e-mail, instant messaging and VoIP/video conferencing reduce the cost of phone calls, couriers and travel.
• Centralized backup and administration: one administrator can manage security, backup and user accounts, so fewer technical staff are needed.
• Less paper and storage: electronic forms and records cut the cost of paper, printing and filing space.

Example: A college office has 20 staff computers. Without a network, each computer would need its own printer, its own copy of the accounting software and its own internet connection. With a LAN, the college buys two shared network printers, one server holding the student records and the accounting software, and one internet connection shared through a router. The cost of printers, software licences and internet subscriptions falls sharply, and staff can access the same student record at the same time without photocopying or moving papers.

A laser printer is a non-impact page printer that forms the image using a laser beam, a photosensitive drum and toner (dry powder ink). The laser draws the page image as an electrostatic charge on the drum, toner sticks to the charged area, and the toner is transferred to paper and fused with heat.

Characteristics

• High printing speed, measured in pages per minute (ppm), and very good print quality (600 dpi to 1200 dpi or more).
• Prints a full page at a time and is quiet, since it is a non-impact printer.
• Uses toner cartridges that print many pages, so the cost per page is low for large volumes.
• Sharp text and graphics; colour laser printers use four toners (cyan, magenta, yellow, black).
• Has its own memory and processor to hold the page before printing.
• The initial cost is higher than an inkjet printer, and colour models are costly.

Applications

• Offices, schools and colleges for reports, letters and exam papers.
• Publishing and desktop publishing work needing high-quality text and graphics.
• Printing of legal documents, invoices, bank statements and certificates in bulk.
• Network printing shared by many users in an office.

Web architecture is the structure of the components and the way they interact to deliver web content and services over the Internet. The most common form is the client-server model, often built in layers (tiers): presentation (browser), application (web server and business logic) and data (database server).

Main components

• Client (web browser): sends HTTP/HTTPS requests and displays HTML, CSS and JavaScript.
• DNS: converts the domain name into the IP address of the server.
• Web server: receives requests and returns static pages or passes the request on (for example Apache, Nginx).
• Application server: runs the server-side code (PHP, Java, Python, Node.js) and business logic.
• Database server: stores and retrieves data.

Data flow

1. The user types a URL such as www.example.com in the browser.
2. The browser asks a DNS server, which returns the IP address of the web server.
3. The browser opens a TCP connection and sends an HTTP request (for example GET /index.html).
4. The web server receives the request. For a static page it reads the file; for a dynamic page it hands the request to the application server.
5. The application server runs the code, queries the database, and receives the data.
6. The server builds the HTML response and sends it back as an HTTP response (status code, headers, body).
7. The browser receives the response, renders the page and fetches extra files (images, CSS, scripts) with further requests.

$\text{Browser} \rightarrow \text{DNS} \rightarrow \text{Web server} \rightarrow \text{Application server} \rightarrow \text{Database} \rightarrow \text{back to Browser}$

(a) A softcopy device is an output device that produces output in a temporary, electronic form which can be viewed but not held on paper, such as a monitor, projector or speaker. (An input device such as the OMR reads marks and sends them to the computer as soft data.)

Optical Mark Reader (OMR)

Working mechanism:

1. A specially printed sheet has small circles or boxes at fixed positions, which the person fills with a dark pencil or pen.
2. The sheet is fed into the scanner, and a light source (LED or laser) shines on the sheet.
3. Marked (dark) areas reflect less light than unmarked areas, and a photo-sensor detects this difference.
4. The reader converts the position of each detected mark into digital data, and software compares it with an answer key or code table.
5. The results are stored or processed by the computer.

Applications: checking multiple-choice examination answer sheets, surveys and questionnaires, voting and lottery tickets, attendance sheets, and application forms for entrance tests.

(b) DOS commands

i. Create the TU directory:

md TU

ii. Display the tree structure of the files and folders in TU:

tree TU /f

iii. Remove the non-empty folders BCA and MCA:

rd /s /q BCA
rd /s /q MCA

iv. Find the IP address of the computer:

ipconfig

v. Check whether a remote device is present on the network:

ping 192.168.1.1

(a) Ambient reality

Ambient reality (ambient computing/intelligence) is an environment in which computing is embedded in the surroundings, so that sensors, smart devices and networks quietly sense the user's context and respond automatically, without the user directly operating a device. Examples are smart homes where lights, temperature and speakers adapt to people, and voice assistants such as Alexa.

Difference from augmented reality

(b) Healing Brush Tool

The Healing Brush Tool is useful because it removes blemishes, spots, scratches, wrinkles and unwanted objects from an image. It samples pixels from one area (source) and paints them over the damaged area while matching the texture, lighting, shading and colour of the destination, so the repair blends naturally and is not visible.

Creating an ID card in Photoshop

1. Choose File > New and create a document of ID card size (for example 3.5 in x 2.2 in, 300 ppi, RGB).
2. Fill the background with a colour or place a design/logo on a new layer.
3. Open the passport photograph, use the Crop Tool to crop the face, and place it onto the card with File > Place; resize with Free Transform (Ctrl+T).
4. Use the Healing Brush (hold Alt to select a clean source, then paint over spots) to clean the photo.
5. Use the Horizontal Type Tool to add the name, ID number, department, address and signature on separate text layers.
6. Add shapes, borders and the institution logo using the Shape tools and layer styles.
7. Arrange the layers, and save the editable file as PSD; export as JPEG or PNG through File > Export for printing.

(a) Fundamental capabilities offered by an operating system

The operating system (OS) is the system software that manages the hardware and gives the user and application programs a convenient interface. Its main capabilities are:

1. Process management: creates, schedules and terminates processes, and allows multitasking.
2. Memory management: allocates and frees main memory for programs, and uses virtual memory.
3. File management: creates, stores, names, organizes, protects and retrieves files and directories.
4. Device management: controls input/output devices through drivers, with buffering and spooling.
5. User interface: provides a command line (CLI) or graphical (GUI) interface to use the computer.
6. Security and protection: passwords, user accounts and permissions to protect data from unauthorized access.
7. Resource allocation and error handling: shares the CPU, memory and devices among users fairly, and detects and reports errors.
8. Networking and communication: supports connection and sharing of resources on a network.
9. Running application software: provides system calls so that programs run without handling hardware directly.

(b) Interactive multimedia

Multimedia means the combined use of several media types, namely text, graphics, audio, video and animation, in one computer-based presentation. It is interactive when the user can control the flow of the content, for example by clicking buttons, choosing links, answering questions or navigating menus, and the system responds. Examples are educational CDs, computer games, e-learning websites and kiosks.

Components of multimedia

• Text: the basic medium for headings, descriptions and instructions, in various fonts and styles.
• Graphics/images: still pictures, drawings, photographs and icons (bitmap and vector).
• Audio: speech, music and sound effects, stored in formats such as MP3 and WAV.
• Video: recorded moving pictures with sound, stored in formats such as MP4 and AVI.
• Animation: the illusion of motion created by displaying a sequence of drawings or 3D models.
• Interactivity (user control): buttons, hyperlinks and menus that let users navigate the content.

When purchasing a new laptop, the buyer should evaluate the following criteria against the needs and budget.

1. Purpose of use: office work, programming, gaming, graphics/video editing or student use decides the required power.
2. Processor (CPU): type (Intel Core i3/i5/i7, AMD Ryzen), number of cores and clock speed decide speed and multitasking.
3. RAM: at least 8 GB for general use, with 16 GB or more for heavy work, and whether it can be upgraded.
4. Storage: SSD is much faster than HDD; capacity (256 GB, 512 GB, 1 TB) and expansion options.
5. Display: size (13 to 17 inch), resolution (Full HD or higher), panel quality and brightness.
6. Graphics card: integrated graphics for general use; dedicated GPU for games, design and video editing.
7. Battery life: hours of backup, which is important for portability.
8. Portability: weight and thickness.
9. Ports and connectivity: USB-A/USB-C, HDMI, card reader, Wi-Fi, Bluetooth.
10. Keyboard, touchpad, speakers and webcam: comfort and quality for daily use.
11. Operating system and software: pre-installed OS and licence.
12. Build quality, brand, warranty and after-sales service: especially local service centres and spare parts.
13. Price and value for money: comparison of specifications at the available budget.

A Geographic Information System (GIS) is a computer-based system for capturing, storing, managing, analyzing and displaying data that is linked to locations on the Earth's surface. It combines maps with database information so that users can see patterns, relationships and trends in spatial data. Examples of use are urban planning, disaster management, navigation, agriculture and land records.

Elements (components) of GIS

1. Hardware: computers, servers, GPS receivers, scanners, digitizers, plotters and mobile devices used to collect, process and display data.
2. Software: GIS programs (ArcGIS, QGIS) with tools to input, store, analyze and display geographic information.
3. Data: the most important element, consisting of spatial data (maps, satellite images, coordinates, in raster or vector form) and attribute data (descriptive information stored in tables).
4. People: the users, analysts, GIS specialists and managers who design, operate and interpret the system.
5. Methods (procedures): the rules, techniques and workflows used for analysis, so that results are accurate and consistent.

a) Retrieve the IP address of a website

nslookup www.tribhuvan-university.edu.np

(ping www.google.com also shows the IP address of the site in its reply.)

b) Move files from one location to another

move C:\Data\report.txt D:\Backup

This moves report.txt from the Data folder on C: to Backup on D:.

c) Delete a non-empty directory

rd /s /q C:\Projects\OldFolder

/s removes the directory with all its files and subfolders and /q suppresses the confirmation prompt.

d) Search for a file or directory

dir C:\ /s /b notes.txt

This searches drive C: and all subfolders for notes.txt. The where command can also be used, for example where /r C:\ notes.txt.

e) Check the available disk space on a drive

dir D:

The last line of the output shows the free bytes. Another option is fsutil volume diskfree D:.

A Database Management System (DBMS) is software that allows users to define, create, store, retrieve, update and control a database, which is an organized collection of related data. It acts as an interface between the database and the users or application programs. Examples are MySQL, Oracle, SQL Server and PostgreSQL.

A flat-file system stores data in separate independent files (for example text or CSV files), with each application managing its own files.

Advantages of DBMS over flat-file system

1. Reduced data redundancy: data is stored once and shared, instead of being duplicated across many files.
2. Data consistency: because of less duplication, there is no conflicting copy of the same data.
3. Data independence: the structure of the data can change without changing the application programs.
4. Data integrity: integrity constraints (primary key, foreign key, check) keep the data accurate and valid.
5. Data security: the DBMS provides user accounts, privileges and access control.
6. Concurrent access: many users can use and update the data at the same time safely.
7. Backup and recovery: automatic mechanisms restore data after failures.
8. Powerful query facility: languages such as SQL make it easy to retrieve data, whereas flat files need special programs.
9. Data sharing and relationships: related data from different tables can be combined easily.

Peer-to-peer (P2P) network: every computer (peer) has equal status and acts as both client and server. Computers share resources directly, with no dedicated server.

Client/Server network: one or more powerful dedicated computers (servers) provide resources and services, and the other computers (clients) request them.

A digital computer works on the input - process - output cycle with storage. The block diagram is shown below.

              +---------------------------------------+
              |        CENTRAL PROCESSING UNIT        |
 +--------+   |   +-----------------+                 |   +---------+
 | INPUT  |-->|   | CONTROL UNIT    |                 |-->| OUTPUT  |
 | UNIT   |   |   +--------+--------+                 |   | UNIT    |
 +--------+   |            |                          |   +---------+
              |   +--------v--------+                 |
              |   | ARITHMETIC &    |                 |
              |   | LOGIC UNIT (ALU)|                 |
              |   +--------+--------+                 |
              +------------|--------------------------+
                           |
                   +-------v--------+
                   |    MEMORY      |
                   | Primary / Secondary |
                   +----------------+

1. Input unit Accepts data and instructions from the user and converts them into binary form that the computer understands. Examples: keyboard, mouse, scanner, microphone, barcode reader.

2. Central Processing Unit (CPU) The brain of the computer, which executes instructions. It has:

• Control Unit (CU): directs and coordinates all operations. It fetches instructions from memory, decodes them, and sends control signals to the ALU, memory and input/output devices.
• Arithmetic and Logic Unit (ALU): performs arithmetic operations (addition, subtraction, multiplication, division) and logical operations (comparisons such as AND, OR, NOT, greater than, equal to).
• Registers: small, very fast storage locations in the CPU that hold the data, address and instruction being processed (for example accumulator, program counter, instruction register).

3. Memory (storage unit)

• Primary memory (main memory): RAM and ROM; holds the data and programs currently in use. RAM is volatile; ROM is non-volatile and stores the start-up program.
• Secondary memory: hard disk, SSD, CD/DVD, pen drive; stores data and programs permanently in large amounts.
• Cache memory: a small, very fast memory between the CPU and RAM that reduces access time.

4. Output unit Converts the binary results produced by the computer into a human-readable form. Examples: monitor, printer, speaker, projector.

Working: the input unit sends data to memory; the control unit fetches instructions and data from memory; the ALU processes them; the result is stored in memory and sent to the output unit.

(a) Memory hierarchy

Memory hierarchy is the arrangement of the different types of computer memory in levels according to speed, cost and capacity. Moving up the hierarchy, memory becomes faster, more costly per byte, smaller in capacity and closer to the CPU. Moving down, it becomes slower, cheaper and larger.

        Registers          (fastest, smallest, costliest)
        Cache memory (L1, L2, L3)
        Main memory (RAM)
        Secondary storage (SSD / HDD)
        Tertiary / offline storage (optical disk, magnetic tape, cloud)  (slowest, largest, cheapest)

1. Registers: inside the CPU; hold the data being processed; access time in nanoseconds or less; capacity of a few bytes.
2. Cache memory: small, very fast SRAM that keeps frequently used data and instructions to reduce the speed gap between CPU and RAM.
3. Main memory (RAM): volatile memory that holds running programs and data; larger (GBs) but slower than cache.
4. Secondary storage: hard disk and SSD; non-volatile, with large capacity (hundreds of GB to TB) and slower access.
5. Tertiary/offline storage: magnetic tapes, optical disks and backup media, used for archives; the cheapest and slowest.

The hierarchy works because of the principle of locality of reference: programs tend to reuse the same data, so a small fast memory can serve most requests.

(b) Layers and features of Photoshop

Layer: a layer in Photoshop is a transparent sheet on which part of an image, text or effect is placed. Layers are stacked on top of each other and together form the final image. Because each element is on its own layer, it can be edited, moved, resized, hidden or deleted without affecting the other layers (non-destructive editing). Layers can have opacity, blending modes, styles and masks.

Main features and tools

• Selection tools: Marquee, Lasso, Magic Wand and Quick Selection select parts of an image.
• Move and Crop tools: move selected content and crop or straighten an image.
• Brush, Pencil and Eraser: paint or erase pixels.
• Clone Stamp and Healing Brush tools: copy pixels and repair blemishes or remove unwanted objects.
• Paint Bucket and Gradient tools: fill areas with colour or gradients.
• Type tool: adds and formats text.
• Shape and Pen tools: draw vector shapes and paths.
• Adjustments: Brightness/Contrast, Levels, Curves, Hue/Saturation for colour correction.
• Filters: blur, sharpen, distort and artistic effects.
• Layer masks, layer styles and blending modes for compositing and effects.
• Zoom, Hand and Eyedropper tools: navigation and colour sampling.
• Support for many file formats (PSD, JPEG, PNG, GIF, TIFF) and RGB/CMYK colour modes.

Primary memory (main memory) is the memory directly accessed by the CPU. It holds the data, instructions and intermediate results of the programs currently being executed. It is fast and has limited capacity, and comprises RAM, ROM and cache memory. RAM is volatile (its contents are lost when power is off), while ROM is non-volatile.

Difference between static RAM (SRAM) and dynamic RAM (DRAM)

Command Line Interface (CLI) operating system: the user interacts with the computer by typing text commands at a prompt. It needs the user to remember commands and syntax, uses little memory and is fast for experts. Examples: MS-DOS, the Linux shell, Windows Command Prompt.

Graphical User Interface (GUI) operating system: the user interacts with the computer through graphical elements such as windows, icons, menus and pointers, using a mouse, keyboard or touch. It is easy to learn and use, but needs more memory and processing power. Examples: Windows, macOS, Ubuntu desktop, Android.

Types of operating system

1. Batch operating system: jobs are collected in groups (batches) and executed one after another without user interaction. Example: early IBM mainframe systems.
2. Multiprogramming/multitasking OS: several programs are kept in memory and the CPU switches among them, so that the CPU is used efficiently. Example: Windows, Linux.
3. Time-sharing (multi-user) OS: many users share the CPU by receiving short time slices, and each user feels they have their own machine. Example: UNIX.
4. Real-time OS (RTOS): responds to inputs within a strict time limit. Used in air traffic control, robots and medical devices. Example: VxWorks.
5. Distributed OS: manages a group of independent computers that work together as a single system.
6. Network OS: runs on a server and provides shared files, printers and user management over a network. Example: Windows Server, Novell NetWare.
7. Mobile OS: designed for smartphones and tablets. Example: Android, iOS.
8. Embedded OS: built into devices such as ATMs and washing machines.

Why DBMS is needed

A DBMS is needed to store and manage large amounts of related data in an organized, shared and secure manner:

• It reduces data redundancy and inconsistency, since data is stored once.
• It allows many users to share and access data at the same time.
• It enforces integrity constraints so that data stays valid.
• It provides security through user accounts and access privileges.
• It provides backup and recovery after failures.
• It gives easy retrieval of information through query languages such as SQL.
• It gives data independence between the stored data and the application programs.

How the relational model represents data and relationships

In the relational model, all data is organized in relations (tables). A table has rows (tuples) and columns (attributes), and each row represents one entity instance, such as one student.

• Data is represented by the values in the rows and columns of tables.
• Relationships are also represented using tables and values, through keys. A primary key uniquely identifies each row. A foreign key in one table holds the primary key value of a row in another table, which links the two tables.

Example:

DeptID is the primary key of Department and a foreign key in Student. The matching values of DeptID show which student belongs to which department. A many-to-many relationship is represented by a separate table that contains the foreign keys of both tables. Related data is combined using the join operation, for example:

SELECT Name, DName FROM Student JOIN Department ON Student.DeptID = Department.DeptID;

DNS (Domain Name System) is a hierarchical, distributed naming system of the Internet that translates human-readable domain names (such as www.example.com) into numeric IP addresses (such as 93.184.216.34) that computers use to locate each other. It works like the phone book of the Internet. When a user enters a domain name, the browser asks a DNS resolver, which queries root, top-level domain and authoritative name servers until the IP address is found and returned. The result is cached to speed up later requests.

Difference between the Internet and an extranet

E-commerce (electronic commerce) is the buying, selling and exchange of goods, services and information over the Internet or other electronic networks. It includes online shopping, online payment, electronic fund transfer and online banking. Examples: Daraz, Amazon, eSewa payments. Common types are B2B, B2C, C2C and C2B.

Benefits of e-commerce

To businesses

• Reaches a global market and a larger number of customers.
• Lower costs, since there is no need for a physical shop and fewer staff.
• Open for business 24 hours a day, 7 days a week.
• Faster transactions and automatic order and inventory handling.
• Easy collection of customer data for marketing.

To customers

• Convenience of shopping from home at any time.
• Wide choice and easy comparison of products and prices.
• Lower prices, discounts and saved travel time.
• Easy access to product reviews and information.
• Many online payment options.

To society

• Creates jobs and new business opportunities.
• Makes goods available in remote areas.
• Reduces paper use and travel.

(a) Uses of word processing software

Word processing software (for example MS Word) is used to create, edit, format, save and print text documents. Its uses include:

• Writing letters, reports, assignments, books, resumes and notices.
• Editing text easily (insert, delete, copy, move, find and replace).
• Formatting text with fonts, sizes, colours, alignment, bullets and numbering.
• Inserting tables, pictures, charts, shapes and hyperlinks.
• Checking spelling and grammar.
• Creating documents in bulk using mail merge.
• Setting up pages with headers, footers, page numbers and margins.
• Saving documents, sharing them and printing.

Major controls in the Layout tab of MS Word

• Margins: sets the space at the top, bottom, left and right of the page.
• Orientation: switches the page between portrait and landscape.
• Size: selects the paper size such as A4, Letter or Legal.
• Columns: divides the text into two or more columns.
• Breaks: inserts page breaks, section breaks and column breaks.
• Line Numbers: numbers the lines of the document.
• Hyphenation: splits long words at line ends automatically.
• Indent: sets left and right indentation of paragraphs.
• Spacing: sets the space before and after paragraphs.
• Position, Wrap Text, Bring Forward, Send Backward, Align, Group and Rotate: arrange objects such as pictures and shapes in the page.

(b) DOS commands

i. Create two folders:

md Folder1 Folder2

ii. Create files in the folders:

echo. > Folder1\file1.txt
echo. > Folder2\file2.txt

(copy nul Folder1\file1.txt also creates an empty file.)

iii. Copy the content of file1.txt to file2.txt:

copy Folder1\file1.txt Folder2\file2.txt

iv. Rename File2.txt as CopiedFile.txt:

ren Folder2\file2.txt CopiedFile.txt

v. Find the IP address of the network:

ipconfig

(a) Computer virus

A computer virus is a malicious program that attaches itself to a legitimate file or program, copies itself and spreads from one file or computer to another, usually without the user's knowledge. It can corrupt or delete data, slow down the system or steal information. It spreads through infected pen drives, email attachments, downloads and websites.

Symptoms of a virus

• The computer runs slowly or hangs and crashes often.
• Programs take long to open, or fail to start.
• Unexpected pop-ups, messages or changed home page.
• Files or folders disappear, are corrupted or change size.
• Strange file names or new unknown files appear.
• The disk fills quickly or free memory suddenly drops.
• Antivirus or Task Manager is disabled or will not open.
• High network or disk activity without reason, and the computer restarts by itself.

Prevention techniques

• Install reliable antivirus software and keep it and its virus definitions updated.
• Keep the operating system and applications updated with security patches.
• Scan pen drives and downloaded files before opening them.
• Do not open email attachments or links from unknown senders.
• Use a firewall.
• Download software only from trusted sources, and avoid pirated software.
• Take regular backups of important data.
• Use strong passwords and limited user accounts.

(b) Mask and editing controls in Photoshop

Use of mask: a mask hides or reveals parts of a layer without erasing any pixels. In a layer mask, painting with black hides the area, painting with white shows it, and gray gives partial transparency. This allows non-destructive editing: the hidden part can be restored anytime. Masks are used for blending images, removing backgrounds, and applying adjustments to selected areas only.

Controls for editing an image

• Crop tool and Image Size/Canvas Size: crop, resize and straighten the image.
• Brightness/Contrast, Levels and Curves: adjust tones and exposure.
• Hue/Saturation and Color Balance: change and correct colours.
• Selection tools (Marquee, Lasso, Magic Wand): edit chosen areas.
• Clone Stamp, Healing Brush and Spot Healing: remove blemishes and unwanted parts.
• Dodge and Burn: lighten or darken specific areas.
• Blur and Sharpen tools and Filters: soften, sharpen or add effects.
• Eraser and Brush: erase or paint on pixels.
• Transform (Ctrl+T), Rotate and Flip: resize, rotate and distort.
• Layers, blending modes, opacity and adjustment layers: combine and control edits.
• Undo and History panel: go back to earlier steps.

Why protocols are needed

A protocol is a set of rules that defines how data is formatted, addressed, sent, received and acknowledged on a network. Protocols are needed because:

• Different devices, hardware and operating systems must understand each other, so a common standard language is needed.
• They define data format, addressing and routing, so that data reaches the right destination.
• They provide error detection and correction, so data is delivered correctly.
• They control flow and sequencing, so a fast sender does not overwhelm a slow receiver and packets are put in the correct order.
• They handle connection setup and termination, and security (for example HTTPS, TLS).
• They allow products from different vendors to work together (interoperability).

Is it secure to transfer data through a network?

Not completely. Data on a network can be intercepted (eavesdropping), modified, stolen or blocked by attackers using sniffing, spoofing, malware, man-in-the-middle and denial-of-service attacks. Security is improved through encryption (SSL/TLS, HTTPS, VPN), firewalls, strong authentication, digital signatures, antivirus and updated systems. With these measures the transfer can be made reasonably secure, but no network is perfectly secure.

OSI model

The Open Systems Interconnection (OSI) model was developed by ISO. It divides network communication into seven layers; each layer provides services to the layer above and uses services of the layer below. At the sender, data goes down from layer 7 to layer 1, with each layer adding its header (encapsulation); at the receiver it moves up from layer 1 to layer 7.

A common memory aid for the layers from 7 to 1 is "All People Seem To Need Data Processing". The model gives a standard reference for designing protocols and for troubleshooting layer by layer.

A computer system consists of the following fundamental components.

1. Hardware The physical parts of the computer.

• Input devices (keyboard, mouse, scanner): send data and instructions into the computer.
• Central Processing Unit (CPU): executes instructions. The control unit directs operations, the ALU does arithmetic and logic, and registers hold data temporarily.
• Memory: primary memory (RAM, ROM, cache) holds data and programs in use; secondary memory (hard disk, SSD) stores data permanently.
• Output devices (monitor, printer, speaker): present the results to the user.

2. Software Programs that instruct the hardware.

• System software: operating system, device drivers and utilities, which manage the hardware and provide a platform for other software.
• Application software: programs for specific tasks such as word processing, spreadsheets and browsers.

3. Data Raw facts and figures that are input and processed into information.

4. People (users) Programmers, administrators and end users who operate the system and use its results.

5. Procedures The instructions and rules for using the system.

Together these components accept input, process it, store it and give output.

Computer memory is the part of the computer that stores data, instructions and results, either temporarily or permanently, so that the CPU can use them. It is measured in bytes (KB, MB, GB, TB).

Memory hierarchy

Memory hierarchy arranges the different types of memory in levels according to speed, cost and capacity. Higher levels are faster, costlier, smaller and closer to the CPU; lower levels are slower, cheaper and larger.

   Registers
   Cache memory (L1, L2, L3)
   Main memory (RAM)
   Secondary storage (SSD / HDD)
   Tertiary storage (optical disk, tape, cloud)

1. Registers: inside the CPU, the fastest and smallest, hold the data being processed.
2. Cache memory: small, fast SRAM that stores frequently used data and instructions to bridge the speed gap between the CPU and RAM.
3. Main memory (RAM): volatile memory holding running programs and data, of larger capacity (GBs) but slower than cache.
4. Secondary memory: hard disk and SSD, non-volatile, large and cheaper per byte, slower to access.
5. Tertiary/offline storage: optical disks, magnetic tapes and backups; the cheapest and slowest, used for archives.

The hierarchy gives a system that is nearly as fast as the fastest memory but with the capacity and cost of the cheapest, based on the principle of locality of reference.

Computer software is the set of programs, data and instructions that tells the hardware what to do and how to do it. It is the intangible part of a computer system; it cannot be touched, while hardware (CPU, memory, disk) can. Without software, hardware is just an idle machine.

Software is broadly divided into:

• System software: operating systems (Windows, Linux), device drivers, language translators (compiler, interpreter, assembler) and utilities.
• Application software: programs for specific user tasks, such as MS Word, a browser, a payroll system or a game.

Program vs software

Every software contains programs, but a program alone is not necessarily software.

Operating System (OS) is system software that manages the computer hardware and software resources and acts as an interface between the user (and application programs) and the hardware. Its main functions are process management, memory management, file management, device management, security and providing a user interface. Examples: Windows, Linux, macOS, Android.

Types of operating systems

1. Batch OS: Similar jobs are collected into a batch and executed one after another without user interaction. Example: early IBM mainframe systems, payroll processing.
2. Multiprogramming / Multitasking OS: Several programs are kept in memory and the CPU switches among them, so the CPU stays busy and the user can run many tasks at once. Example: Windows, Linux.
3. Time-sharing OS: The CPU time is divided into small slices and given to each user or process in turn, giving each the illusion of a dedicated machine. Example: UNIX.
4. Multiuser OS: Allows many users to use the system at the same time through terminals. Example: UNIX, Linux servers.
5. Real-time OS (RTOS): Responds to input within a strict time limit. Hard real-time (missile control, pacemaker) and soft real-time (multimedia streaming). Example: VxWorks, FreeRTOS.
6. Distributed OS: Manages a group of independent computers connected by a network and makes them appear as one system, sharing load and resources.
7. Network OS: Runs on a server and provides file, printer and user services to client computers. Example: Windows Server, Novell NetWare.
8. Mobile OS: Designed for smartphones and tablets. Example: Android, iOS.

Open-source operating systems (source code freely available to view, modify and redistribute): Linux and its distributions (Ubuntu, Fedora, Debian, Red Hat), FreeBSD, Android (AOSP), Chromium OS, and Haiku.

Database: A database is an organised collection of related data stored electronically so that it can be easily accessed, managed, updated and retrieved. It is usually managed by a Database Management System (DBMS) such as MySQL, Oracle, MS Access or SQL Server. Example: a college database storing students, courses and results.

Main functions of a database / DBMS

• Data storage and organisation: stores large amounts of data in tables in a structured way.
• Data retrieval: queries (for example SQL) fetch required records quickly.
• Data manipulation: insert, update and delete records.
• Data security: user accounts, permissions and access control.
• Data integrity: constraints (primary key, foreign key, not null) keep data accurate and consistent.
• Reducing redundancy: the same data is stored once and shared.
• Concurrency control: many users can use the data at the same time safely.
• Backup and recovery: restores data after failure.
• Report generation: produces summaries and reports.

Types of database

1. Hierarchical database: data is arranged in a tree with parent-child (one-to-many) relationships. Example: IBM IMS.
2. Network database: records are linked in a graph, allowing many-to-many relationships. Example: IDS, IDMS.
3. Relational database (RDBMS): data is stored in tables (rows and columns) related through keys. Most widely used. Example: MySQL, Oracle, PostgreSQL, SQL Server.
4. Object-oriented database: stores data as objects as in object-oriented programming. Example: db4o, ObjectDB.
5. NoSQL database: non-tabular, flexible storage for big data (document, key-value, column, graph). Example: MongoDB, Cassandra, Redis.
6. Distributed database: data is spread over several computers or locations but works as one database. Example: Google Spanner.

Browsing is the activity of locating and viewing information on the World Wide Web using a web browser such as Chrome, Firefox, Edge or Safari. The user types a URL or searches by keyword, follows hyperlinks from page to page and views text, images, audio and video. A browser requests pages from web servers and renders the received HTML for display.

Home page of a website is the main or first page of a website, shown when a visitor enters the site's domain name (for example www.example.com). It acts as the introduction and table of contents of the site, giving navigation links to other pages. The term also means the page a browser opens at start-up, which the user can set.

Three Internet protocols

1. HTTP / HTTPS (HyperText Transfer Protocol): The protocol used by the web to transfer web pages between a browser (client) and a web server. The client sends a request, the server sends a response. HTTPS adds encryption using SSL/TLS for security. Default ports: 80 (HTTP), 443 (HTTPS).
2. FTP (File Transfer Protocol): Used to upload and download files between a client and a server over a network. It uses separate control (port 21) and data connections and normally needs a username and password.
3. SMTP (Simple Mail Transfer Protocol): Used to send e-mail from a client to a mail server and between mail servers (port 25). Receiving mail uses POP3 or IMAP.

Other examples are TCP/IP, DNS, Telnet and DHCP.

a. Multimedia vs Hypermedia

Multimedia is the combination of more than one type of media, namely text, graphics, images, audio, video and animation, in a single presentation. It is usually presented in a linear manner and may or may not be interactive. Examples: a video lecture, a CD-based encyclopaedia, a PowerPoint slide show.

Hypermedia is an extension of hypertext in which multimedia elements are connected through hyperlinks, so the user can navigate non-linearly by clicking links from one piece of information to another. Example: the World Wide Web.

Every hypermedia is multimedia, but not every multimedia is hypermedia.

b. GUI vs CUI

GUI (Graphical User Interface) lets the user interact with the computer using graphical elements such as windows, icons, menus and pointer (mouse). Example: Windows, macOS.

CUI (Character/Command User Interface) lets the user interact by typing text commands at a prompt. Example: MS-DOS, Linux terminal.

Why networks matter in the 21st century

A computer network connects computers and devices so that they can exchange data and share resources. Its importance today comes from:

• Communication: email, video calls, messaging and social media all run on networks.
• Resource sharing: printers, files, databases and internet connections are shared, which lowers cost.
• Information access: the Internet gives access to education, news, research and e-government services.
• Business and e-commerce: online banking, digital wallets (eSewa, Khalti), online shopping and remote work depend on networks.
• Cloud and storage: data and software are available anywhere and are backed up centrally.
• Reliability and scalability: data can be replicated, and new users or devices can be added easily.

Role of transmission media in network design

Transmission media are the physical or wireless paths that carry signals. The choice of medium sets the speed, range, cost, security and immunity to noise of the network.

Guided (wired) media

• Twisted pair (UTP/STP): cheap and easy to install. Used for LANs up to about 100 m. Twisting reduces interference.
• Coaxial cable: a copper core with shielding. It is more noise-resistant than twisted pair and was used for cable TV and older Ethernet.
• Optical fibre: carries light pulses. It gives very high bandwidth, long distance, low attenuation and immunity to electromagnetic interference. It is used for backbones and ISP links, but it costs more.

Unguided (wireless) media

• Radio waves / Wi-Fi: mobility and easy installation inside buildings.
• Microwave and satellite: long distance and remote areas, with high cost and delay.
• Infrared / Bluetooth: short-range, line-of-sight links between nearby devices.

In design, fibre is chosen for backbones, UTP for desktops, and wireless where mobility or difficult terrain makes cabling impractical.

Functions of network devices

(a) ImageReady vs Photoshop, and selection tools

Selection tools in Photoshop

• Marquee tools: Rectangular, Elliptical, Single Row and Single Column, for regular-shaped selections.
• Lasso tools: Lasso (freehand), Polygonal Lasso (straight segments) and Magnetic Lasso (snaps to edges).
• Quick Selection tool: paints a selection that expands to edges.
• Magic Wand tool: selects pixels of similar colour, controlled by the tolerance setting.
• Object Selection tool and Select > Color Range: select by object or by sampled colours.
• Move tool and Crop tool are not selection tools. The Pen and Path tools can be converted to selections.

(b) PowerPoint, purpose, and Slide Sorter vs Slide Show view

PowerPoint is Microsoft's presentation software. It builds a presentation from slides containing text, images, charts, tables, audio, video, animation and transitions.

Purpose: to present information visually and clearly to an audience in teaching, business meetings, seminars and project defences. It can also print handouts or be shared as PDF or video.