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CS360

CS360. Windows Programming. Last Week. We Covered the principles behind web services Introduced the .NET framework Reviewed object-oriented programming Started learning about C#. C# Statements and Expressions. Very similar to C++, with some changes to increase robustness

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CS360

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  1. CS360 Windows Programming CS360 Windows Programming

  2. Last Week • We • Covered the principles behind web services • Introduced the .NET framework • Reviewed object-oriented programming • Started learning about C# CS360 Windows Programming

  3. C# Statements and Expressions • Very similar to C++, with some changes to increase robustness • No ‘->’ or ‘::’; all qualifications use ‘.’ • Local variables must be initialized before use • if, while, do require bool condition • goto can’t jump into blocks • switch statement – no fall through (empty case OK) • case labels can be strings CS360 Windows Programming

  4. Types • FCL is a library of types • Classes – today • Structs – today • Interfaces – next time • Enumerations – next time • Delegates – next time CS360 Windows Programming

  5. Classes • Classes contain • Fields - data members in C++ • Methods - member functions in C++ • Properties - expose data using get and set • Events - define notifications that class can hire CS360 Windows Programming

  6. Example class Rectangle { // Fields protected int width = 1; protected int height = 1; // Methods (constructors) public Rectangle () {} public Rectangle (int cx, int cy) { Width = cx; Height = cy; } } CS360 Windows Programming

  7. Example (cont.) // Properties public int Width { get { return width; } set { if (value > 0) width = value; else throw new ArgumentOutOfRangeException ( "Width must be 1 or higher"); } } CS360 Windows Programming

  8. Example (cont.) public int Height { get { return height; } set { if (value > 0) height = value; else throw new ArgumentOutOfRangeException ( "Height must be 1 or higher"); } } public int Area { get { return width * height; } } CS360 Windows Programming

  9. Example (cont.) Rectangle rect = new Rectangle (); Rectangle rect = new Rectangle (3, 4); rect.Width *= 2; int area = rect.Area; CS360 Windows Programming

  10. Structs struct Point { public int x; public int y; public Point (int x, int y) { this.x = x; this.y = y; } } CS360 Windows Programming

  11. Reference and Value Types • Classes are reference types • Structs are value types CS360 Windows Programming

  12. Common Type System Object Value Reference Built-in (primitive) data types Examples: int, double, … Size is specific Allocated on Stack Assignment copies value Cannot derive from other types User defined types: structs Deallocated when defining block exits Examples: Classes, Arrays, Interfaces, Delegates Allocated on managed heap Assignment copies reference Garbage collected CS360 Windows Programming

  13. Stack and Heap • Memory is a collection of bytes • Imagine each box as one byte long • Each byte can hold a number between 0-255. Why? • Each byte has an address CS360 Windows Programming

  14. Stack and Heap • Whenever a variable is created it is added on to the stack • Variables are added sequentially (i.e. l-r, t-b) • No value for an empty byte • No holes allowed in memory. Why? • Stack pointer pointsto end of usedmemory A B C CS360 Windows Programming

  15. Stack and Heap • Problem: what do we do with dynamic variables? • Solution: use a heap • Stack is used forfixed size variables only • Stack pointer infirst four bytes ofstack Stack pointer A B B B C CS360 Windows Programming

  16. Stack and Heap • Variables created on the heap are scattered throughout the heap • Heap contains holes • Each variable has a header listing • Size of variable • Address of nextvariable stack heap CS360 Windows Programming

  17. Example Heap Stack Static void Main() { Ref r1 = new Ref(); Val v1 = new Val(); } Class Ref { public int x; } struct Val { public int x; } CS360 Windows Programming

  18. Example Heap Stack Static void Main() { Ref r1 = new Ref(); Val v1 = new Val(); } Class Ref { public int x; } struct Val { public int x; } r1 x = 0 v1 x = 0 CS360 Windows Programming

  19. Example Heap Stack Static void Main() { Ref r1 = new Ref(); Val v1 = new Val(); r1.x = 5; v1.x = 5; } Class Ref { public int x; } struct Val { public int x; } r1 x = 5 v1 x = 5 CS360 Windows Programming

  20. Example Heap Stack Static void Main() { Ref r1 = new Ref(); Val v1 = new Val(); r1.x = 5; v1.x = 5; Ref r2 = r1; Val v2 = v1; } Class Ref { public int x; } struct Val { public int x; } r1 x = 5 v1 x = 5 r2 v2 x = 5 CS360 Windows Programming

  21. Summary • Completed p. 27 - 38 • Next time we will complete chapter 2 CS360 Windows Programming

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