NIOS CS 330 — Theory Study Portal

Number systems and conversions between decimal, binary, octal, and hexadecimal — extremely high frequency in NIOS exams.

• Decimal (Base 10): Uses digits 0–9. Our everyday number system.
• Binary (Base 2): Uses only 0 and 1. Computer's native language. Each digit = 1 bit. 8 bits = 1 byte.
• Octal (Base 8): Uses digits 0–7. Shorthand for binary (group of 3 bits).
• Hexadecimal (Base 16): Uses 0–9 and A–F (A=10, B=11, C=12, D=13, E=14, F=15).
• Dec → Binary: Divide by 2 repeatedly, read remainders bottom-up.
• Dec → Octal: Divide by 8 repeatedly, read remainders bottom-up. (258)₁₀ = (402)₈
• Dec → Hex: Divide by 16 repeatedly. (2748)₁₀ = (ABC)₁₆
• Hex → Dec: Multiply each digit by 16^position. (BDF)₁₆ = 11×256 + 13×16 + 15 = 3039
• ASCII: American Standard Code for Information Interchange. 'A'=65, 'B'=66, 'C'=67, 'D'=68, 'a'=97.
• Boolean Logic: AND, OR, NOT gates. AND: both inputs 1 → output 1. OR: any 1 → output 1. NOT: inverts.
• Bit, Nibble, Byte: 1 bit, 4 bits, 8 bits respectively. 1 KB = 1024 bytes.

• OS Definition: System software that manages hardware and software resources, acts as interface between user and hardware.
• Functions of OS: Process management, memory management, file management, device management, security, UI.
• Types of OS: Batch, Time-sharing, Real-time, Distributed, Network, Single-user, Multi-user.
• Batch OS: Jobs collected, processed in batches without user interaction. E.g. payroll systems.
• Time-sharing OS: Multiple users share CPU time simultaneously. Each user gets a time slice.
• Real-time OS: Processes data instantly. Used in ATM, missile systems, air traffic control.
• Popular OS: Windows, Linux, macOS, Android, iOS, Ubuntu.
• Shell: Interface between user and OS kernel. Two types: CLI (Command Line) and GUI.
• Process vs Program: A program is static code; a process is a running program.
• Multitasking vs Multiprogramming: Multitasking = one user, multiple tasks. Multiprogramming = multiple programs in memory.

• Data Communication: Transfer of data between devices via transmission medium (wired/wireless).
• Components: Sender, Receiver, Message, Medium, Protocol.
• Transmission Modes: Simplex (one-way, e.g. TV), Half-duplex (both ways, not simultaneous, e.g. walkie-talkie), Full-duplex (both ways simultaneously, e.g. phone).
• Bandwidth: Maximum data transfer capacity of a channel. Measured in bps (bits per second).
• Network Types: LAN (Local, within building), WAN (Wide, across cities/countries), MAN (Metropolitan, city-wide), PAN (Personal).
• Topologies: Bus (single cable), Star (central hub), Ring (circular), Mesh (every device connected to every other), Tree (hierarchical).
• Bus Topology: All devices on single cable. Failure of cable = entire network fails. Simple, cheap.
• Star Topology: Central hub/switch. Hub failure = network down. Easy to troubleshoot.
• Ring Topology: Data travels in one direction. Each node acts as repeater. Token passing.
• Mesh Topology: Every node connected to every other. Most reliable but expensive. n(n-1)/2 connections for n nodes.
• Hub vs Switch: Hub broadcasts to all; Switch sends only to intended recipient.
• Router: Connects different networks, routes data packets. Uses IP addresses.
• Firewall: Security system monitoring incoming/outgoing traffic. Blocks unauthorized access.
• Transmission Media: Twisted pair, Coaxial cable, Fiber optic (wired); Radio, Microwave, Infrared (wireless).

• Internet: Global network of computers connected via TCP/IP protocol.
• TCP/IP: Foundation protocol of Internet. TCP = Transmission Control Protocol. IP = Internet Protocol.
• ARPANET: Advanced Research Projects Agency Network — predecessor of Internet, developed by US DoD in 1969.
• WWW (World Wide Web): System of hypertext documents accessed via Internet. Created by Tim Berners-Lee.
• URL: Uniform Resource Locator — address of a webpage. E.g., http://www.example.com
• HTTP/HTTPS: HyperText Transfer Protocol. S = Secure (encrypted). Foundation of web data exchange.
• DNS: Domain Name System — translates domain names to IP addresses.
• ISP: Internet Service Provider — provides internet access (e.g., BSNL, Airtel, Jio).
• IP Address: Unique numerical label for each device. IPv4 = 32-bit (e.g. 192.168.1.1), IPv6 = 128-bit.
• Video Conferencing: Real-time visual and audio communication over the internet between multiple participants. E.g., Zoom, Google Meet.
• FTP: File Transfer Protocol — for transferring files between computers.
• SMTP/POP/IMAP: Email protocols. SMTP = sending. POP = receiving (downloads). IMAP = receiving (stays on server).
• Browser: Software to access web pages. E.g., Chrome, Firefox, Edge, Safari.

• Word Processor: Software to create, edit, format, print text documents. Writer supports creating/formatting/printing data.
• OpenOffice Writer: Free, open-source word processor. Equivalent to MS Word.
• Toolbars: Formatting toolbar (font style, size, bold, italic, underline), Standard toolbar (save, open, print), Drawing toolbar.
• Copying Text: Select text → Edit > Copy (Ctrl+C) → Place cursor → Edit > Paste (Ctrl+V). Creates duplicate of selected text.
• Cut vs Copy: Cut (Ctrl+X) moves text; Copy (Ctrl+C) duplicates text.
• Indentation: Space between text and page margin. Types: First-line, Hanging, Left, Right indentation.
• Spacing: Distance between lines (line spacing) or paragraphs. Single, 1.5, Double spacing.
• Components of Writer Window: Title bar, Menu bar, Toolbars, Ruler, Work area, Status bar, Scroll bars.
• Mail Merge: Creating multiple personalized letters using a data source (like a database or spreadsheet).
• Find & Replace: Ctrl+H — finds text and replaces with new text throughout document.

• Spreadsheet: Application to store data in rows and columns, perform calculations. Lotus 1-2-3 is an example.
• OpenOffice Calc: Free, open-source spreadsheet. Equivalent to MS Excel.
• Cell: Intersection of a row and column. Identified by column letter + row number (e.g., A1, B3).
• Worksheet: Individual page of a spreadsheet. Also called a sheet tab.
• Workbook: Collection of worksheets in one file.
• Docking Toolbars: Provides quick access to various tools and functions.
• Alignment: Position of data with respect to the boundary of the cell (left, right, center, justify).
• Sorting: Arranging data in ascending (A–Z, 0–9) or descending (Z–A, 9–0) order.
• Formula: Starts with = sign. E.g., =A1+B1, =SUM(A1:A10), =AVERAGE(B1:B5).
• Charts: Visual representation of data. Types: Bar, Line, Pie, Column.
• Absolute vs Relative Reference: Relative (A1) changes when copied. Absolute ($A$1) stays fixed.

• Presentation Software: Used to create slideshows with text, images, animations. OpenOffice Impress.
• Impress: Can add Text, Pictures, Audio, Video — All of the above! (PYQ favorite)
• Views in Impress: Normal view (editing), Slide Sorter view (organize slides), Notes view (speaker notes), Outline view, Slide Show view.
• Slide Sorter View: Organizes and manages sequence of slides. (PYQ: "Which view allows you to organize and manage the sequence?")
• Handouts View: Used to print multiple slides on a single page as thumbnails. (PYQ: "Which view is used to print multiple slides?")
• Ctrl+Q: Close a presentation. (PYQ answer!)
• Slide Transitions: Animation effects when moving from one slide to next.
• Animation: Effects applied to objects within a slide (text, images).
• Master Slide: Template that controls the background, fonts, and color scheme for all slides.

• C++: General-purpose, object-oriented programming language developed by Bjarne Stroustrup as extension of C.
• Header Files: #include<iostream.h> for I/O, <math.h> for math functions (log, exp, sqrt), <string.h> for strings, <ctype.h> for character functions.
• math.h / cmath: Contains exp(x), log(x), log10(x), sqrt(x), pow(x,y), abs(x). (PYQ: "What is header file for log(x)?" → math.h)
• Data Types: int (integer), float (decimal), double (precise decimal), char (single character), bool (true/false), void.
• char Data Type: Stores a single character. Size = 1 byte. E.g., char ch = 'A';
• ASCII Values: 'A'=65, 'B'=66, 'C'=67, 'D'=68 … 'Z'=90, 'a'=97 … 'z'=122, '0'=48.
• cin / cout: cin = input (keyboard), cout = output (screen). Both need iostream.h.
• Variables: Named memory location. Must be declared before use. E.g., int x = 5;
• Operators: Arithmetic (+,-,*,/,%), Relational (<,>,==,!=), Logical (&&, ||, !), Assignment (=, +=), Increment (++), Decrement (--).
• Type Casting: Converting one data type to another. E.g., (float)5/2 = 2.5, not 2.

• OOP: Object-Oriented Programming — paradigm based on objects containing data and code.
• Class: Blueprint/template for creating objects. Defines data members and member functions.
• Object: Instance of a class. Has state (data) and behavior (functions).
• Encapsulation: Binding data and functions together in a class. Hiding internal details.
• Abstraction: Showing only essential information, hiding complexity.
• Inheritance: One class acquires properties of another. Promotes code reuse.
• Polymorphism: Same function name, different behavior. "Many forms".
• Data Hiding: Restricting access to class members using private/protected.
• Access Specifiers: public (accessible everywhere), private (only within class — default), protected (within class and derived classes).
• Member functions: Functions defined inside a class to operate on class data.
• Dot (.) operator: Accesses public members of an object. E.g., obj.display();
• :: (Scope resolution) operator: Used to define member functions outside a class. E.g., void ClassName::funcName()
• Inline Member Function: Function defined inside class body. Compiler replaces call with code directly for speed.

• if-else: Conditional execution. if(condition){...} else {...}
• switch-case: Multi-way branch. Each case must have break; to avoid fall-through. default runs if no case matches.
• Fall-through in switch: Without break, execution continues to next case. (PYQ: grade='B' without break → outputs "GoodFairInvalid")
• while loop: Checks condition before executing. while(i<4){...}
• for loop: Initialization, condition, increment in one line. for(int i=0; i<5; i++){...}
• do-while loop: Executes at least once, checks condition after. do{...}while(condition);
• break: Exits the loop/switch immediately.
• continue: Skips current iteration, goes to next.
• Infinite loop: Loop with always-true condition. while(i>0); with semicolon after while = infinite loop! (PYQ trap!)
• Nested loops: Loop inside a loop. Inner loop completes all iterations for each outer iteration.

• Function: Named block of code performing a specific task. Promotes code reuse.
• Parts: Function declaration (prototype), function definition, function call.
• Function Prototype: Declaration before main(). E.g., void fun1(int); — tells compiler function exists. (PYQ calls this "Statement 1")
• Call by Value: Copies variable's value. Changes inside function don't affect original. void change(int b) — b is a copy.
• Call by Reference: Passes address. Changes affect original. void fun1(int& b) — & means reference. (PYQ: output of fun1 with int& b → a becomes 15*15=225)
• Return type: void returns nothing. int returns integer. float returns decimal.
• Default arguments: Function parameters with default values if not provided.
• Function overloading: Same function name, different parameter types/number. Example of polymorphism.
• math.h functions: sqrt(), pow(), log(), exp(), abs() — frequently tested.
• Library functions: Pre-written functions in header files (strlen, strcpy in string.h, etc.)

• Array: Collection of elements of same data type stored at contiguous memory locations.
• Declaration: int arr[5]; — array of 5 integers. Index starts from 0, so arr[0] to arr[4].
• Accessing elements: arr[0]=10; arr[1]=20; etc.
• Array size: If declared int arr[n], valid indices are 0 to n-1.
• 2D Array: int matrix[3][4]; — 3 rows, 4 columns.
• String as array: char name[20]; — stores string. Ends with null character '\0'.
• Selection Sort: Find minimum, swap with first element. Repeat for remaining. O(n²) time. (Frequently asked in PYQ — write the program!)
• Bubble Sort: Compare adjacent elements, swap if out of order. Repeat passes.
• Searching: Linear search (check each element), Binary search (sorted array, divide and conquer).
• Array as function argument: Array name without [] passes base address (by reference automatically).

• Structure: User-defined data type grouping different data types under one name. Keyword: struct.
• Declaring a structure: struct Student { int roll; char name[20]; float marks; };
• Creating objects: Student s1, s2; (create two objects of type Student). (PYQ: Statement 1 always asks to create two objects)
• Accessing members: Using dot operator. s1.roll = 101; cin >> s1.name;
• Input for member: cin >> s1.salary; (PYQ: Statement 2 always asks to input a member)
• Structure vs Class: Structure members are public by default. Class members are private by default.
• Typedef: Creates an alias for a data type. typedef int INTEGER; → INTEGER x = 5;
• Enumerated (enum): User-defined type with named integer constants. enum Days {MON=1, TUE, WED, THU, FRI, SAT, SUN};
• Nested Structure: Structure inside another structure.

• Class syntax: class ClassName { private: ...; protected: ...; public: ... };
• Members: Data members (variables) and member functions (methods) inside a class.
• Constructor: Special function with same name as class, no return type. Called automatically when object is created. Initializes objects.
• Destructor: Same name as class with ~ prefix. Called automatically when object is destroyed. Frees memory.
• Default constructor: No parameters. If not defined, compiler creates one automatically.
• Parameterized constructor: Takes arguments to initialize with specific values.
• Copy constructor: Creates a new object as copy of existing object.
• this pointer: Implicit pointer pointing to current object. Used when member and parameter have same name.
• Objects as function arguments: Can be passed like variables.
• Array of objects: Student s[5]; — array of 5 Student objects.

• Inheritance: Derived class inherits properties of base class. Promotes reuse. Syntax: class Derived : accessSpecifier Base {}
• Types of Inheritance: Single, Multiple, Multilevel, Hierarchical, Hybrid.
• Single: One base, one derived class.
• Multiple: One derived class, multiple base classes. class C : public A, public B.
• Multilevel: Chain — A→B→C. C inherits B which inherits A.
• Hierarchical: One base class, multiple derived classes.
• Hybrid: Combination of two or more types.
• Access in inheritance (public mode): public members of base → public in derived. protected members → protected. Private → NOT inherited.
• Access in inheritance (private mode): Both public and protected members of base become private in derived.
• Accessible from objects of class: Only PUBLIC members. (PYQ question type!)
• Employee→Department→Project (PYQ standard code): Project inherits Employee publicly, Department privately. From Project object, accessible = public of Employee + public of Project. Protected of Employee becomes protected in Project.

• Pointer: Variable that stores the memory address of another variable.
• Declaration: int *p; — p is a pointer to int.
• Address operator &: Returns address of variable. p = &x; — p holds address of x.
• Dereference operator *: Accesses value at address. *p gives value at address stored in p.
• PYQ classic: int x=965; int *y=&x; cout<<*y; → Output: 965 (dereferences pointer)
• Pointers allow dynamic memory allocation using new and delete. (PYQ True/False — TRUE)
• Object pointers: Can access only PUBLIC members of object (NOT private). (PYQ True/False — FALSE for accessing private)
• new operator: Allocates memory at runtime. int *p = new int;
• delete operator: Frees dynamically allocated memory. delete p;
• Pointer arithmetic: p++ moves pointer to next element based on data type size.
• NULL pointer: Pointer not pointing to any address. int *p = NULL;

• File: Collection of logically related records stored on secondary storage.
• Header file for file I/O: <fstream.h> (PYQ: "Writing data on file requires ____ header file" → fstream.h)
• File classes: ifstream (input/read), ofstream (output/write), fstream (both).
• Opening a file: Using open() function. E.g., outfile.open("data.txt");
• Closing a file: outfile.close(); — always close after use.
• File modes: ios::in (read), ios::out (write), ios::app (append — opens in append mode), ios::binary.
• ios::app: Opens file in APPEND mode — adds data to end, doesn't overwrite. (PYQ fill-in-the-blank!)
• EOF: End Of File marker. Used to stop reading.
• eof() function: Returns true when end of file is reached.
• get() and put(): Character-level file I/O.
• getline(): Reads entire line from file.

• DBMS: Database Management System — software to store, organize, retrieve data. E.g., MySQL, Oracle, MS Access.
• RDBMS: Relational DBMS — stores data in tables (relations) with rows and columns. E.g., MySQL.
• Table/Relation: Collection of rows and columns representing data about an entity.
• Attribute: Column in a table. Represents a property of an entity. E.g., Name, Age, Salary.
• Tuple/Record: A single row in a table.
• Domain: Set of valid values for an attribute. E.g., Age domain = positive integers.
• Degree: Number of columns (attributes) in a table.
• Cardinality: Number of rows (tuples) in a table.
• Primary Key: Uniquely identifies each row. Cannot be NULL or duplicate. E.g., Roll Number.
• Candidate Key: All columns that CAN be a primary key (unique + not null). Primary key is chosen from candidate keys.
• Alternate Key: Candidate keys NOT chosen as primary key.
• Foreign Key: Column referencing primary key of another table. Creates relationships.
• Data Models: Conceptual (ERD), Logical (RDBMS tables), Physical (actual storage).
• SQL: Structured Query Language — language to interact with RDBMS.
• DDL: Data Definition Language — CREATE, ALTER, DROP (structure of tables).
• DML: Data Manipulation Language — SELECT, INSERT, UPDATE, DELETE (data in tables).
• DCL: Data Control Language — GRANT, REVOKE (permissions).
• SELECT command: Retrieves data. SELECT * FROM table WHERE condition;
• INSERT command: Adds new records. INSERT INTO table VALUES(...);
• UPDATE command: Modifies existing records. UPDATE table SET col=val WHERE condition;
• DELETE with WHERE: Deletes specific rows matching condition. Without WHERE = deletes ALL rows!
• CREATE TABLE: CREATE TABLE name (col1 datatype, col2 datatype, PRIMARY KEY(col));
• ALTER TABLE: Modifies table structure — add/drop/modify columns.
• Default Constraint: Assigns default value to column if none provided.
• VARCHAR vs CHAR: VARCHAR = variable length (efficient). CHAR = fixed length.

• HTML: HyperText Markup Language — standard language for creating web pages.
• Tag: Special word enclosed within < > angle brackets. (PYQ MCQ — answer is C: < >)
• Structure tags: <html>, <head>, <title>, <body> — ALL of these are structural tags.
• Heading tags: <h1> to <h6>. H1 = biggest. H6 = smallest. (PYQ: "biggest heading = H1")
• <b>: Bold text. Correct format: <b>text</b>. (PYQ MCQ — answer is C: <b> OCTOBER </b>)
• <p>: Paragraph tag — adds space before and after text block.
• <br>: Line break — no closing tag! Goes to next line. (PYQ: <br> has no ending tag)
• P vs BR: <p> creates a new paragraph (with space). <br> just moves to next line.
• Align attribute: Attribute (not a tag or command) — specifies alignment. (PYQ MCQ — answer: attribute)
• <BODY> attributes: bgcolor (background color), text (text color), background (image). "Text" is the correct attribute. (PYQ answer)
• HTML file extension: Saved as .html or .htm. Opened in browser (Chrome, Firefox, Edge).
• <hr>: Horizontal rule (line). <hr size=5 width=50%> creates a line with specified size and width.
• Attribute vs Tag: Tag is the element (<b>), attribute is a property of a tag (align, bgcolor, src).

• <img> tag: Inserts image. Attributes: src (URL/path), alt (alternative text), height, width, border, align.
• src attribute: Specifies URL/path of image. (PYQ: "attribute used to specify URL of image" → src)
• Recommended image format for web: None of the listed options (.pdf, .doc, .ppt) — answer is "None of these" in PYQ context, but in reality JPEG/PNG are recommended.
• border attribute: Specifies border width of image. (PYQ: "attribute to specify width of border for image" → border)
• Ordered List <ol>: Numbered list. Items in <li> tags. (PYQ: "create numbered/ordered list" → <ol>)
• Unordered List <ul>: Bulleted list. Items in <li> tags. (PYQ: "create bulleted list" → <ul>)
• <li>: List item tag — used inside both <ol> and <ul>. (PYQ: "tag to add items in ordered list" → <li>)
• Definition List <dl>: Contains <dt> (term) and <dd> (description).
• size attribute of <img>: NO such attribute! Use height and width instead. (PYQ: "size attribute specifies?" → "No such attribute for image in HTML")
• Writing HTML code (PYQ pattern): Create heading with <hN>, bold text with <b>, background color in <body bgcolor="color">, image with <img src="file.jpg" height=X width=Y>.

• Data Structure: Way of organizing and storing data for efficient access and modification.
• Types: Linear (Array, Stack, Queue, Linked List) and Non-linear (Tree, Graph).
• Stack: LIFO — Last In, First Out. Operations: Push (insert), Pop (remove from top).
• Queue: FIFO — First In, First Out. Operations: Enqueue (add to rear), Dequeue (remove from front).
• Linked List: Nodes linked via pointers. Each node has data and pointer to next. Dynamic size.
• Tree: Hierarchical structure. Root, nodes, leaves, parent-child relationships.
• Binary Tree: Each node has at most 2 children.
• Algorithm: Step-by-step procedure to solve a problem.
• Complexity: Time complexity (speed), Space complexity (memory).
• Sorting algorithms: Selection sort O(n²), Bubble sort O(n²), Quick sort O(n log n).

• Project: Temporary endeavor with defined start/end to create unique product/service.
• Project Management: Planning, organizing, directing, controlling resources to achieve project goals.
• Project Life Cycle: Initiation → Planning → Execution → Monitoring → Closure.
• Gantt Chart: Bar chart showing project schedule. Shows tasks vs. time.
• PERT: Program Evaluation and Review Technique — estimates time for tasks.
• Risk Management: Identifying and mitigating potential project risks.
• Stakeholders: People affected by or involved in the project.

• Entrepreneur: Person who creates and manages a business, taking financial risk for profit.
• Characteristics: Risk-taking, Innovation, Leadership, Decision-making, Persistence.
• Business Plan: Document describing business goals, strategies, market analysis, financial plan.
• Start-up: New business venture in early stage, often technology-based.
• Self-employment: Working for oneself rather than an employer.

• Communication: Exchange of information between sender and receiver.
• Types: Verbal (spoken), Written, Non-verbal (body language), Visual.
• Effective Communication: Clear, Concise, Complete, Courteous, Correct (5 Cs).
• Email Etiquette: Professional subject line, formal language, proofread before sending.
• Resume: Document summarizing education, skills, experience for job applications.
• Interview skills: Preparation, punctuality, confidence, follow-up.