# Unit 2: Introduction to OOP and C++ (CA203) ## Need and Advantages of OOP - **Need**: procedural programs become hard to maintain, data is exposed, and little reuse; OOP models real-world problems and manages complexity. - **Advantages**: **reusability** (inheritance), **data hiding and security**, modularity, easy maintenance and extension, close mapping to real world, polymorphism and productivity. ## Characteristics of Object-Oriented Languages - **Objects and classes**, **encapsulation**, **data abstraction**, **inheritance**, **polymorphism** (compile-time: overloading; run-time: virtual functions), dynamic binding and message passing. - Examples: C++, Java, Smalltalk, Python. ## C++ Programming Basics C++ was developed by **Bjarne Stroustrup** at Bell Labs (early 1980s) as "C with Classes"; it is a superset of C. ### Basic Program Structure ``` #include using namespace std; int main() { cout << "Hello"; return 0; } ``` Parts: preprocessor directive, namespace, `main()`, statements ending with `;`. ### Input/Output Using cin/cout - `cout << x;` uses the **insertion operator <<** (output stream); `cin >> x;` uses **extraction operator >>**; cascading: `cout << a << b;`. - `endl` or `'\n'` for new line; `cerr` for errors. ### Preprocessor Directives and Comments - `#include`, `#define`, `#ifdef`; comments `// single line` and `/* multi-line */`. ### Data Types | Type | Notes | |---|---| | **int** (short, long) | Integer, 4 bytes typical | | **char** | 1 byte | | **float, double** | Real numbers, 4 and 8 bytes | | bool, void, wchar_t | Additional types | - Modifiers: signed, unsigned, short, long. - **Enumerated data types**: `enum colour {RED, GREEN, BLUE};` user-defined set of named integer constants; in C++ the enum name is a type. ### Manipulators Format output, from `` and ``: `endl`, `setw(n)`, `setprecision(n)`, `setfill(c)`, `fixed`, `hex`, `dec`, `left`, `right`. Example: `cout << setw(8) << 25;` ### Operators - Arithmetic, relational, logical, assignment, increment/decrement, bitwise, conditional `?:`, `sizeof`. - C++ specific: **scope resolution `::`**, `new`, `delete`, pointer-to-member `.*` and `->*`, insertion/extraction. ### Library Functions Built-in functions from headers: `` (`sqrt`, `pow`, `sin`, `abs`), `` (`strlen`, `strcpy`), `` (`toupper`, `isdigit`), `` (`rand`, `exit`). **[Figure: Structure of a C++ program]** Sections for headers, class declarations, member function definitions and main. ### C vs C++ | C | C++ | |---|---| | Procedural | Object-oriented + procedural | | `printf/scanf` | `cout/cin` | | No classes | Classes, inheritance | | No overloading | Function and operator overloading | | `malloc/free` | `new/delete` | ## Likely Exam Questions 1. Discuss the need and advantages of object-oriented programming. 2. Explain the characteristics of OOP languages. 3. Write the basic structure of a C++ program. 4. Explain cin, cout and manipulators with examples. 5. What are enumerated data types? (2 marks) 6. Differentiate C and C++.