Information Technology Class-XII Practice Flashcards

COMPUTER NETWORKING: OVERVIEW AND ADVANTAGES

• Definition of Computer Network: A computer network is a collection of interconnected computers and other hardware devices linked through communication channels to facilitate communication and resource sharing among users.
• Key Advantages of Networking:
  • Program Security & Easy Maintenance: Programs are stored in locked, read-only spaces on servers to prevent unauthorized copying or tampering.
  • Secure Database & Personal Work Files: Data redundancy across multiple computers ensures information is not lost if a single unit fails. Password protection prevents malicious deletion.
  • Remote Booting: Eliminates the need for physical boot disks at workstations.
  • Collaboration via File Sharing: Publicly accessible storage for assignments, tests, and results. Facilitates communication through Email, Video Conferencing, and Instant Messaging.
  • Resource Sharing: Users share peripheral devices like printers, DVD drives, scanners, and digital projectors, reducing installation and maintenance costs.
• Network Components:
  • Hardware: Computers (Desktops, Laptops, Smart Phones), peripheral devices, transmission media, and networking devices (Hub, Switch, Router, Modem).
  • Nodes: Any computer or peripheral device connected to a network.
  • Software: Communication protocols and translation formats (Gateways).
• Network Classification by Size:
  • Personal Area Network (PAN): Organized around an individual in a single building (range: up to $10\,m$ radius).
  • Local Area Network (LAN): Covers a room, building, or campus (range: up to $10\,km$ radius).
  • Metropolitan Area Network (MAN): Spans an entire city or campus (range: up to $100\,km$ radius).
  • Wide Area Network (WAN): Crosses city, country, or continental limits (No upper limit; e.g., the Internet).

TRANSMISSION MEDIA AND TOPOLOGIES

• Network Topology: The layout pattern of interconnections between nodes.
  • Point-to-Point: Direct link between two computers; fast and reliable.
  • Bus: Uses a single central cable (backbone) with terminators at both ends to prevent signal reflection.
  • Star: Each node connects to a central hub or switch. Robust, but fails if the central hub fails.
  • Ring: Circular connection where data travels in one direction. Each computer acts as a signal booster.
  • Tree: Combination of Bus and Star topologies; highly expandable.
  • Mesh: Every node has a direct connection to every other node; high security and volume capacity.
• Guided (Wired) Media:
  • Twisted Pair/Ethernet: Copper wires twisted to reduce noise. Types include Unshielded (UTP) and Shielded (STP). Max length: $100\,m$.
  • Co-axial Cable: Inner copper conductor with a braided metal shield. Used for TV and high-speed LAN ($10\,Mbps$). Baseband ($75\,Ω$) is for digital; Broadband ($50\,Ω$) is for analog.
  • Optic-fiber Cable: Thin glass/plastic strands transmitting light pulses via total internal reflection. Features a Core, Cladding, and Buffer coating. Highest speed ($>100\,Gbps$) and immune to electromagnetic interference.
• Unguided (Wireless) Media:
  • Radio Waves: Range $3\,kHz$ to $3\,GHz$. Omnidirectional and can penetrate buildings.
  • Microwaves: Range $0.3\,GHz$ to $300\,GHz$. Requires line-of-sight alignment.
  • Infrared: Range $300\,GHz$ to $400,000\,GHz$. Short-range ($5\,m$), cannot pass through solid objects.
  • Bluetooth: Radio waves in $2.402\,GHz$ to $2.480\,GHz$. Connects up to 8 devices simultaneously.
  • Satellite Link: Uses Geostationary ($35,838\,km$ height), MEO, or LEO orbits. Uplink frequency ($1.6\,GHz$ to $30.0\,GHz$) is always higher than Downlink ($1.5\,GHz$ to $20.0\,GHz$).

INTERNET PROTOCOLS AND ADDRESSING

• Internet History: Proposed by J C R Licklider (1962); Packet switching developed by Leonard Kleinrock. ARPANET (1969) was the first network. Tim Berners-Lee created WWW (1992).
• Internet Access Types:
  • Dial-up: Uses analog phone lines. Shell (text only), TCP/IP (graphics support), or ISDN ($128\,Kbps$).
  • DSL (Digital Subscriber Line): Asymmetric (ADSL) features higher downstream than upstream. Uses filters to separate voice and data.
  • Cable Modem: Uses HFC (Hybrid Fiber Coax). Always connected but bandwidth is shared by neighbors.
• Network Identifiers:
  • MAC Address: Permanent 12-digit hexadecimal (48-bit) physical address assigned by the manufacturer (e.g., $00:A0:C9:14:C8:35$).
  • IP Address:
    • IPv4: 32-bit address represented as four octets ($0-255$). E.g., $216.27.63.135$.
    • IPv6: 128-bit address developed to handle the exhaustion of available IPv4 addresses.
• Internet Protocols:
  • TCP/IP: Suite governing data transmission and packet reconstruction.
  • SMTP/POP3/IMAP: Protocols for sending and receiving email.
  • FTP: For file transfers between computers.
  • HTTP/HTTPS: For hyper-text transfer between servers and browsers.
  • Telnet: For logging into remote computers.

NETWORK SECURITY AND CYBER CRIMES

• Cyber Crimes:
  • Hacking: Breaking into networks for destruction or monetary gain. Includes Web Hijacking.
  • Virus: Malicious code requiring human interaction to spread. Types: Boot Infectors, System Infectors, Executable Program Infectors.
  • Worm: Self-replicated code that spreads automatically without a host program.
  • Trojan Horse: Malicious program disguised as legitimate software.
  • DoS (Denial of Service): Flooding a resource with requests to crash it and deny legitimate access.
  • Spoofing: Pretending to be someone else by forging IP addresses or Email headers.
• Security Tools:
  • Firewall: Hardware/software barrier between internal and external networks that filters traffic.
  • Encryption: Transforming plaintext to ciphertext.
    • Symmetric: Same key for encryption and decryption.
    • Asymmetric: Public key for encryption, Private key for decryption.
  • Digital Signature: Ensures authenticity and non-repudiation of electronic documents.
  • Cookies: Message strings (up to $4\,kB$) stored by browsers to track user activity.
• Cyber Laws in India: The Information Technology Act, 2000 (IT Act) and IT Amendment Act, 2008.
  • Section 43: Penalties for data theft and computer damage (Civil liability).
  • Section 66: Criminality for data theft (Section 66F specifically addresses Cyber Terrorism with life imprisonment).

PROGRAMMING FUNDAMENTALS AND JAVA LIBRARIES

• Object Oriented Programming (OOP): Focuses on Data Encapsulation, Inheritance, and Polymorphism.
• Access Specifiers:
  • Public: Accessible anywhere.
  • Protected: Accessible in the same package and by subclasses in other packages.
  • Default: Accessible only within the same package.
  • Private: Accessible only within the defined class.
• Inheritance: Process where one class (Subclass) acquires properties of another (Superclass) using the extends keyword.
  • Forms: Single, Multiple (via Interfaces), Multilevel, Hierarchical, and Hybrid.
• Common Java Methods:
  • String Class: length(), concat(), toLowerCase(), toUpperCase(), trim(), substring(start, end).
  • Math Class: Math.pow(a, b) for powers; Math.round(a) for rounding values.
• JDBC (Java Database Connectivity): API to connect Java to databases like MySQL.
  • Drivers: JDBC-ODBC Bridge (Type 1), Native-API (Type 2), Network Protocol (Type 3), and Thin Driver (Type 4).
  • Core Classes: DriverManager, Connection, Statement, ResultSet.

RELATIONAL DATABASE MANAGEMENT SYSTEM AND MYSQL

• Database Transaction: A group of tasks treated as a single unit.
• ACID Properties: Atomicity, Consistency, Isolation, Durability.
• Transaction Control:
  • COMMIT: Saves changes permanently.
  • ROLLBACK: Reverts changes to the last commit.
  • SAVEPOINT: Creates intermediate markers within a transaction.
• Aggregate Functions:
  • MAX(), MIN(), AVG(), SUM(), COUNT().
  • COUNT(*) includes all rows; COUNT(column) excludes NULLs.
• SQL Clauses:
  • GROUP BY: Groups results based on column values.
  • HAVING: Applies conditions to groups (used where WHERE cannot handle aggregate functions).
• Joins and Sets:
  • Equi-Join: Extracts data from multiple tables based on common column equality.
  • Foreign Key: A column in one table referencing the Primary Key of another to ensure referential integrity.
  • UNION: Combines output of two SELECT statements (requires identical column count and types).
• MySQL Specifics:
  • Constraints: PRIMARY KEY, NOT NULL, UNIQUE, ENUM, SET.
  • Operators: LIKE (pattern matching using % and _), BETWEEN (range), IN (list matching).
  • Built-in Functions:
    • CONCAT_WS(separator, str1, str2): Concatenate with separator.
    • TRUNCATE(x, d): Chops off digits to $d$ decimal places without rounding.
    • SYSDATE() vs NOW(): SYSDATE() returns time of execution while NOW() returns constant time of statement start.

IT APPLICATIONS: E-BUSINESS AND DIGITAL TRANSACTIONS

• E-Business Models:
  • B2B: Business-to-Business (e.g., wholesale).
  • B2C: Business-to-Consumer (e.g., Amazon, Flipkart).
  • C2C: Consumer-to-Consumer (e.g., eBay).
  • G2C: Government-to-Citizen (e.g., portal for birth certificates).
• UI Design (Front-End Interface):
  • CLI: Command Line (text only).
  • GUI: Graphical User Interface (uses icons and widgets).
  • Components: JTextField (single line), JTextArea (multi-line), JRadioButton (exclusive choice), JCheckBox (multiple choices).
• ER Model (Entity-Relationship):
  • Entity: Object (Rectangle).
  • Relationship: Association (Diamond).
  • Attribute: Property (Ellipse). Attributes can be Composite, Single-valued, or Multi-valued.
• Digital Payments in India:
  • USSD (*99#): Banking for feature phones without internet.
  • AEPS: Aadhaar-enabled fingerprint-based payments.
  • UPI: Real-time interoperable bank transfers.
  • PoS Types: Physical, Mobile (mPoS), and Virtual PoS.
  • NEFT vs RTGS: NEFT settlements in hourly batches; RTGS for large-value real-time transfers (Minimum $Rs. 2\,lakh$).