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Csc153 chapter 02

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  • 1. Microsoft Visual C# 2010 Fourth Edition Chapter 2 Using Data
  • 2. Objectives• Learn about declaring variables• Display variable values• Learn about the integral data types• Learn about floating-point data types• Use arithmetic operatorsMicrosoft Visual C# 2010, Fourth Edition 2
  • 3. Objectives (contd.)• Learn about the bool data type• Learn about numeric type conversion• Learn about the char data type• Learn about the string data type• Define named constants and enumerations• Accept console inputMicrosoft Visual C# 2010, Fourth Edition 3
  • 4. Declaring Variables• Constant – Cannot be changed after a program is compiled• Literal constant – Its value is taken literally at each use• Variable – A named location in computer memory that can hold different values at different points in time• Data type – Describes the format and size of (amount of memory occupied by) a data itemMicrosoft Visual C# 2010, Fourth Edition 4
  • 5. Microsoft Visual C# 2010, Fourth Edition 5
  • 6. Declaring Variables (contd.)• Variable declaration – Statement that names a variable and reserves storage – Example: int myAge = 25;• You can declare multiple variables of the same type – In separate statements on different lines• You can declare two variables of the same type in a single statement – By using the type once and separating the variable declarations with a commaMicrosoft Visual C# 2010, Fourth Edition 6
  • 7. Displaying Variable ValuesMicrosoft Visual C# 2010, Fourth Edition 7
  • 8. Displaying Variable Values (contd.)Microsoft Visual C# 2010, Fourth Edition 8
  • 9. Displaying Variable Values (contd.)Microsoft Visual C# 2010, Fourth Edition 9
  • 10. Displaying Variable Values (contd.)Microsoft Visual C# 2010, Fourth Edition 10
  • 11. Displaying Variable Values (contd.)• Format string – A string of characters that optionally contains fixed text – Contains one or more format items or placeholders for variable values• Placeholder – Consists of a pair of curly braces containing a number that indicates the desired variable’s position • In a list that follows the stringMicrosoft Visual C# 2010, Fourth Edition 11
  • 12. Displaying Variable Values (contd.)Microsoft Visual C# 2010, Fourth Edition 12
  • 13. Displaying Variable Values (contd.)• Formatting output int num1 = 4, num2 = 56, num3 = 789; Console.WriteLine(“{0, 5}”, num1); Console.WriteLine(“{0, 5}”, num2); Console.WriteLine(“{0, 5}”, num3);• Concatenate strings – Using the plus (+) signMicrosoft Visual C# 2010, Fourth Edition 13
  • 14. Using the Integral Data Types• Integral data types – Types that store whole numbers – byte, sbyte, short, ushort, int, uint, long, ulong, and char• Variables of type int – Store (or hold) integers, or whole numbers• Shorter integer types – byte, sbyte (which stands for signed byte), short (short int), or ushort (unsigned short int)Microsoft Visual C# 2010, Fourth Edition 14
  • 15. Using Floating-Point Data Types• Floating-point number – Contains decimal positions• Floating-point data types – float • Can hold up to seven significant digits of accuracy – double • Can hold 15 or 16 significant digits of accuracy – decimal • Has a greater precision and a smaller range • Suitable for financial and monetary calculationsMicrosoft Visual C# 2010, Fourth Edition 15
  • 16. Using Floating-Point Data Types (contd.)• Significant digits – Specifies the mathematical accuracy of the value• Suffixes – Put an F after a number to make it a float – Put a D after it to make it a double – Put an M after it to make it a decimal• Scientific notation – Includes an E (for exponent)Microsoft Visual C# 2010, Fourth Edition 16
  • 17. Formatting Floating-Point Values• C# displays floating-point numbers in the most concise way it can – While maintaining the correct value• Standard numeric format strings – Strings of characters expressed within double quotation marks that indicate a format for output – Take the form X0 • X is the format specifier; 0 is the precision specifier• Format specifiers – Define the most commonly used numeric format typesMicrosoft Visual C# 2010, Fourth Edition 17
  • 18. Formatting Floating-Point Values (contd.)Microsoft Visual C# 2010, Fourth Edition 18
  • 19. Using the Standard Binary Arithmetic Operators• Binary operators – Use two values (operands)• Operator precedence – Rules that determine the order in which parts of a mathematical expression are evaluated – Multiplication, division, and remainder always take place prior to addition or subtraction in an expression – You can override normal operator precedence with parenthesesMicrosoft Visual C# 2010, Fourth Edition 19
  • 20. Using the Standard Binary Arithmetic Operators (contd.)Microsoft Visual C# 2010, Fourth Edition 20
  • 21. Using Shortcut Arithmetic Operators• Add and assign operator – Example: bankBal += bankBal * interestRate; – Variations: –=, *=, and /=• Prefix increment operator – Example: ++someValue;• Postfix increment operator – Example: someValue++;• Unary operator – Use only one value• Decrement operator (--)Microsoft Visual C# 2010, Fourth Edition 21
  • 22. Using the bool Data Type• Boolean variable – Can hold only one of two values—true or false – Declare a Boolean variable with type bool• Comparison operator – Compares two items – An expression containing a comparison operator has a Boolean valueMicrosoft Visual C# 2010, Fourth Edition 22
  • 23. Using the bool Data Type (contd.)Microsoft Visual C# 2010, Fourth Edition 23
  • 24. Understanding Numeric Type Conversion• Arithmetic with variables or constants of the same type – Result retains the same type• Arithmetic with operands of dissimilar types – C# chooses a unifying type for the result – Implicitly (or automatically) converts nonconforming operands to the unifying type • Type with the higher type precedenceMicrosoft Visual C# 2010, Fourth Edition 24
  • 25. Understanding Numeric Type Conversion (contd.)• Implicit cast – Automatic transformation that occurs when a value is assigned to a type with higher precedence• Explicit cast – Placing the desired result type in parentheses • Followed by the variable or constant to be castMicrosoft Visual C# 2010, Fourth Edition 25
  • 26. Using the char Data Type• char data type – Holds any single character• Place constant character values within single quotation marks• Escape sequence – Stores a pair of characters – Begins with a backslash – Pair of symbols represents a single characterMicrosoft Visual C# 2010, Fourth Edition 26
  • 27. Using the char Data Type (contd.)Microsoft Visual C# 2010, Fourth Edition 27
  • 28. Using the string Data Type• string data type – Holds a series of characters• Values are expressed within double quotation marks• Comparing strings – Use == and != – Methods Equals(), Compare(), CompareTo()Microsoft Visual C# 2010, Fourth Edition 28
  • 29. Using the string Data Type (contd.)Microsoft Visual C# 2010, Fourth Edition 29
  • 30. Using the string Data Type (contd.)Microsoft Visual C# 2010, Fourth Edition 30
  • 31. Using the string Data Type (contd.)• Use the length property of a string to determine its length – The length of “water” is 5• Use the Substring() method to extract a portion of a string from a starting point for a specific lengthMicrosoft Visual C# 2010, Fourth Edition 31
  • 32. Using the string Data Type (contd.)Microsoft Visual C# 2010, Fourth Edition 32
  • 33. Defining Named Constants• Named constant – Often simply called a constant – An identifier whose contents cannot change – Created using the keyword const• Programmers usually name constants using all uppercase letters – Inserting underscores for readability• Self-documenting statement – Easy to understand even without program commentsMicrosoft Visual C# 2010, Fourth Edition 33
  • 34. Working with Enumerations• An enumeration is a set of constants represented by identifiers• The following is an enumeration called DayOfWeek: enum DayOfWeek { SUNDAY, MONDAY, TUESDAY, WEDNESDAY THURSDAY, FRIDAY, SATURDAY }Microsoft Visual C# 2010, Fourth Edition 34
  • 35. Working with Enumerations (contd.)• By default, enumeration values are integers – Can specify otherwise by including a colon and a type name after the enumeration name• The identifiers in an enumeration are often meant to hold consecutive values – When you don’t supply values, they start at 0 and increment by 1 – In the DayOfWeek enumeration, SUNDAY is 0, MONDAY is 1, and so onMicrosoft Visual C# 2010, Fourth Edition 35
  • 36. Accepting Console Input• Interactive program – A program that allows user input• Console.ReadLine() method – Accepts user input from the keyboard – Accepts all of the characters entered by a user until the user presses Enter – Characters can be assigned to a string – Must use a conversion method to convert the input string to the proper typeMicrosoft Visual C# 2010, Fourth Edition 36
  • 37. Accepting Console Input (contd.)Microsoft Visual C# 2010, Fourth Edition 37
  • 38. Accepting Console Input (contd.)Microsoft Visual C# 2010, Fourth Edition 38
  • 39. You Do It• Activities to explore – Declaring and Using variables – Performing Arithmetic – Working with Boolean Variables – Using Escape Sequences – Writing a Program that Accepts User InputMicrosoft Visual C# 2010, Fourth Edition 39
  • 40. Summary• Constant: cannot be changed after compilation• Can display variable values with Write() or WriteLine()• Nine integral data types: byte, sbyte, short, ushort, int, uint, long, ulong, and char• Three floating-point data types: float, double, and decimal• Use the binary arithmetic operators +, –, *, /, and % to manipulate values in your programs• Shortcut arithmetic operatorsMicrosoft Visual C# 2010, Fourth Edition 40
  • 41. Summary (contd.)• A bool variable can be true or false• Implicit cast versus explicit cast• char data type holds any single character• string data type holds a series of characters• Named constants are program identifiers whose values cannot change.• Console.ReadLine() method accepts user inputMicrosoft Visual C# 2010, Fourth Edition 41