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Module 3 : using value type variables
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- 2. Overview Common TypeSystem Naming Variables Using Built-in Data Types Creating User-Defined Data Types Converting Data Types
- 3. Common Type System Overview of CTS Comparing Value and Reference Types Comparing Built-in and User-Defined Value Types Simple Types
- 4. Overview of CTS CTS supports both value and reference types Reference Type Type Value Type
- 5. Comparing Value andReference Types Value types: Directly contain their data Each has its own copy of data Operations on one cannot affect another Reference types: Store references to their data (known as objects) Two reference variables can reference same object Operations on one can affect another
- 6. Comparing Built-in andUser- Defined Value Types Examples of built-in value types: int float Examples of user-defined value types: enum struct User-Defined Value Types Built-in Type
- 7. Simple Types Identifiedthrough reserved keywords int // Reserved keyword - or - System.Int32
- 8. Naming Variables Rules and Recommendations for Naming Variables C# Keywords Quiz: Can You Spot Disallowed Variable Names?
- 9. Rules and Recommendationsfor Naming Variables Rules Use letters, the underscore, and digits Recommendations Avoid using all uppercase letters Avoid starting with an underscore Avoid using abbreviations Use PascalCasing naming in multiple-word names different Different Answer42 42Answer BADSTYLE _poorstyle BestStyle Msg Message
- 10. C# Keywords Keywordsare reserved identifiers Do not use keywords as variable names Results in a compile-time error Avoid using keywords by changing their case sensitivity abstract, base, bool, default, if, finally int INT; // Poor style
- 11. Quiz: Can YouSpot the Disallowed Variable Names? char $diskPrice; char middleInitial; int 12count; float this; 2 3 4 1 int __identifier;5
- 12. Using Built-in DataTypes Declaring Local Variables Assigning Values to Variables Compound Assignment Common Operators Increment and Decrement Operator Precedence
- 13. Declaring Local Variables Usually declared by data type and variable name: Possible to declare multiple variables in one declaration: --or-- int itemCount; int itemCount, employeeNumber; int itemCount, employeeNumber;
- 14. Assigning Values toVariables Assign values to variables that are already declared: Initialize a variable when you declare it: You can also initialize character values: int employeeNumber; employeeNumber = 23; int employeeNumber = 23; char middleInitial = 'J';
- 15. Compound Assignment Addinga value to a variable is very common There is a convenient shorthand This shorthand works for all arithmetic operators itemCount = itemCount + 40; itemCount += 40; itemCount -= 24;
- 16. Common Operators Common Operators •Equality operators • Relational operators • Conditional operators • Increment operator • Decrement operator • Arithmetic operators • Assignment operators Example == != < > <= >= is && || ?: ++ - - + - * / % = *= /= %= += -= <<= >>= &= ^= |=
- 17. Increment and Decrement Changing a value by one is very common There is a convenient shorthand This shorthand exists in two forms itemCount += 1; itemCount -= 1; itemCount++; itemCount--; ++itemCount; --itemCount;
- 18. Operator Precedence OperatorPrecedence and Associativity Except for assignment operators, all binary operators are left-associative Assignment operators and conditional operators are right- associative
- 19. Creating User-Defined Data Types Enumeration Types Structure Types
- 20. Enumeration Types Definingan Enumeration Type Using an Enumeration Type Displaying an Enumeration Variable enum Color { Red, Green, Blue } Color colorPalette = Color.Red; Console.WriteLine(“{0}”, colorPalette); // Displays Red
- 21. Structure Types Defininga Structure Type Using a Structure Type Employee companyEmployee; companyEmployee.firstName = "Joe"; companyEmployee.age = 23; public struct Employee { public string firstName; public int age; }
- 22. Converting Data Types Implicit Data Type Conversion Explicit Data Type Conversion
- 23. Implicit Data TypeConversion To Convert int to long: Implicit conversions cannot fail May lose precision, but not magnitude using System; class Test { static void Main( ) { int intValue = 123; long longValue = intValue; Console.WriteLine("(long) {0} = {1}", intValue, longValue); } }
- 24. Explicit Data TypeConversion To do explicit conversions, use a cast expression: using System; class Test { static void Main( ) { long longValue = Int64.MaxValue; int intValue = (int) longValue; Console.WriteLine("(int) {0} = {1}", longValue, intValue); } }
- 25. Review Common TypeSystem Naming Variables Using Built-in Data Types Creating User-Defined Data Types Converting Data Types