Data Types and Expressions

Transcription

1 2 Data Types and Expressions C# Programming: From Problem Analysis to Program Design C# Programming: From Problem Analysis to Program Design 1 4th Edition

2 Chapter Objectives C# Programming: From Problem Analysis to Program Design 2

3 Chapter Objectives (continued) C# Programming: From Problem Analysis to Program Design 3

4 Chapter Objectives (continued) C# Programming: From Problem Analysis to Program Design 4

5 Data Representation 0/ C# Programming: From Problem Analysis to Program Design 5

6 Bits and Bytes 6

7 Decimal Number System 7

8 Decimal Number System M 100K 10K , = 203,465

9 Data Representation (continued) Table 2-1 Binary equivalent of selected decimal values C# Programming: From Problem Analysis to Program Design 9

10 Binary Number System (continued) Figure 2-2 Decimal equivalent of

11 Binary Number System = 36 Figure 2-1 Base-10 positional notation of 36 11

12 Binary Number System Figure 2-1 Base-10 positional notation of

13 Data Representation (continued) ' ' '\u20ac' 13

14 Data Representation (continued) ASCII Table

15 Data Representation (continued)

16 Data Representation (continued) Console.WriteLine('\u00D1');

17 Data Representation (continued) 17

18 Memory Locations for Data customername, productcode, addressline1, savingaccountbalance 18

19 Reserved Words in C# 19

20 Contextual Keywords Table 2-4 C# contextual keywords Never use these words as variable names It is a very bad idea!!! 20

21 Naming Conventions Eg: FirstName, LastName Eg: firstname, lastname, savingaccountbalance 21

22 Examples of Valid Names (Identifiers) Table 2-5 Valid identifiers 22

23 Examples of Invalid Names (Identifiers) Table 2-6 Invalid identifier 23

24 Variables type identifier = expression; 24

25 Types, Classes, and Objects int, string C# Programming: From Problem Analysis to Program Design 25

26 Type, Class, and Object Examples Table 2-7 Sample data types C# Programming: From Problem Analysis to Program Design 26

27 Predefined Data Types Common Type System (CTS) Divided into two major categories Figure 2-3.NET common types 27

28 Value and Reference Types Figure 2-4 Memory representation for value and reference types 28

29 Value Types Figure 2-5 Value type hierarchy 29

30 Value Types Integral: 123 Floating point: 1.57e+3 (same as 1570) Decimal: 1.23 Boolean true / false Struct class Person {name, age, sex } Enumerated enum Days { Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday }; enum Months : byte { Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec }; Figure 2-5 Type Examples 30

31 Value Types (continued) 31

32 Integral Data Types byte & sbyte char int & uint long & ulong short & ushort 32

33 Data Types Table 2-9 Values and sizes for integral types 33

34 Examples of Integral Variable Declarations int studentcount; // number of students in the class int ageofstudent = 20; // age-originally initialized to 20 int numberofexams; // number of exams int coursesenrolled; // number of courses enrolled 34

35 Floating-Point Types Table 2-10 Values and sizes for floating-point types 35

36 Examples of Floating-Point Declarations double extraperson = 3.50; double averagescore = 70.0; double priceofticket; double gradepointaverage; float totalamount = 23.57f; // extraperson originally set // to 3.50 // averagescore originally set // to 70.0 // cost of a movie ticket // grade point average // note the f must be placed after // the value for float types 36

37 Decimal Types Table 2-11 Value and size for decimal data type Examples decimal endowmentamount = M; decimal deficit; 37

38 Boolean Variables false bool undergraduatestudent; bool moredata = true; 38

39 Strings string studentname; string coursename = "Programming I"; string twolines = "Line1\nLine2"; 39

40 Making Data Constant const const type identifier = expression; const double TAX_RATE = ; const int SPEED = 70; const char HIGHEST_GRADE = 'A'; 40

41 Assignment Statements variable = expression; 41

42 Examples of Assignment Statements int numberofminutes, count, minintvalue; numberofminutes = 45; count = 0; minintvalue = ; count = count + 1; numberofminutes = 10 + Delay(clerkId); 42

43 Examples of Assignment Statements char firstinitial, yearinschool, punctuation, enterkey, lastchar; firstinitial = 'B'; yearinschool = '1'; punctuation = ';'; enterkey = '\n'; lastchar = '\u005a'; eurosymbol= '\u20ac'; // newline escape character // Unicode character 'Z' // Unicode character ' ' 43

44 Examples of Assignment Statements (continued) double accountbalance, weight; bool isfinished; accountbalance = ; weight = 1.7E-3; //scientific notation may be used isfinished = false; //declared previously as a bool //Notice no quotes used 44

45 Examples of Assignment Statements (continued) decimal amountowed, deficitvalue; amountowed = m; // m or M must be suffixed to deficitvalue = M; // decimal data types 45

46 Examples of Assignment Statements (continued) string asaying, filelocation; asaying = "First day of the rest of your life!\n"; filelocation 46

47 Examples of Assignment Statements (continued) Figure 2-7 Impact of assignment statement 47

48 Arithmetic Operations resultvariable = operand1 operator operand2; 48

49 Basic Arithmetic Operations Figure 2-8 Result of 67 % 3 49

50 Basic Arithmetic Operations (continued) string result; string fullname; string firstname = "Daenerys"; string lastname = "Targaryen"; fullname = firstname + " " + lastname; //now fullname is "Daenerys Targaryen" 50

51 Concatenation Figure 2-9 String concatenation 51

52 Basic Arithmetic Operations (continued) num++; // num = num + 1; --value1; // value = value 1; int num = 100; Console.WriteLine(num++); // Displays 100 Console.WriteLine(num); // Displays 101 Console.WriteLine(++num); // Displays

53 Basic Arithmetic Operations (continued) Figure 2-10 Declaration of value type variables 53

54 Basic Arithmetic Operations (continued) Figure 2-11 Change in memory after count++; statement executed 54

55 Basic Arithmetic Operations (continued) int num = 100; Console.WriteLine(num++); //prints 100 Console.WriteLine(num); //prints 101 Console.WriteLine(++num); //prints 102 C# Programming: From Problem Analysis to Program Design 55

56 Basic Arithmetic Operations (continued) Figure 2-12 Results after statement is executed 56

57 Compound Operations 57

58 Basic Arithmetic Operations (continued) answer = 100; answer += 50 * 3 / 25 4; 50 * 3 = / 25 = = =

59 Order of Operations Table 2-14 Operator precedence 59

60 Order of Operations (continued) Figure 2-13 Order of execution of the operators 60

61 Mixed Expressions double answer; answer = 10 / 3; // Does not produce double answer2; answer2 = 10.0 / 3; // produces int value1 = 440, anothernumber = 70; double value2 = ; value2 = value1; // ok, stored in value2 61

62 Mixed Expressions int value1 = 440; double value2 = ; value1 = value2; // syntax error as shown in Figure 2-14 double int 62

63 Mixed Expressions (continued) (type) expression examaverage = (exam1 + exam2 + exam3) / (double) count; int value1 = 0, anothernumber = 75; double value2 = , anotherdouble = 100; value1 = (int) value2; // value1 = 100 value2 = (double) anothernumber; // value2 =

64 Mixed Expressions (continued) Convert int v1 = Convert.ToInt32(1.999); // v1 is 1 long v2 = Convert.ToInt64("5.7777"); // v2 is string v3 = Convert.ToString(1.999); // v3 is "1.999" char v4 = Convert.ToChar(65); // v4 is 'A' 64

65 Formatting Output 65

66 Formatting Output (continued) Table 2-15 Examples using format specifiers 66

67 Numeric Format Specifiers 67

68 Numeric Format Specifiers (continued) 68

69 Custom Numeric Format Specifiers Table 2-17 Custom numeric format specifiers 69

70 Custom Numeric Format Specifiers (continued) 70

71 Width Specifier Console.WriteLine("{0,10:F0}{1,8:C}", 9, 14); 9 $14.00 //Right justified values

72 Programming Example CarpetCalculator 72

73 Data Needs for the CarpetCalculator Table 2-18 Variables 73

74 Nonchanging Definitions for the CarpetCalculator Side Note: 1 yard = 3 feet 1 sqy = 9 sqf Table 2-19 Constants 74

75 CarpetCalculator Example 75

76 Algorithm for CarpetCalculator Example Figure 2-17 CarpetCalculator flowchart 76

77 Algorithm for the CarpetCalculator Example (continued) Figure 2-18 Structured English for the CarpetCalculator example 77

78 CarpetCalculator Example (continued) Figure 2-19 Class diagram for the CarpetCalculator example 78

79 CarpetCalculator Example (continued) Figure 2-20 Revised class diagram without methods 79

80 /* CarpetCalculator.cs Author: Doyle */ using System; namespace CarpetExample { class CarpetCalculator { static void Main( ) { const int SQ_FT_PER_SQ_YARD = 9; const int INCHES_PER_FOOT = 12; const string BEST_CARPET = "Berber"; const string ECONOMY_CARPET = "Pile"; int roomlengthfeet = 12, roomlengthinches = 2, roomwidthfeet = 14, roomwidthinches = 7; double roomlength, roomwidth, carpetprice, numofsquarefeet, numofsquareyards, totalcost; 80

81 roomlength = roomlengthfeet + (double) roomlengthinches / INCHES_PER_FOOT; roomwidth = roomwidthfeet + (double) roomwidthinches / INCHES_PER_FOOT; numofsquarefeet = roomlength * roomwidth; numofsquareyards = numofsquarefeet / SQ_FT_PER_SQ_YARD; carpetprice = 27.95; //per square yard totalcost = numofsquareyards * carpetprice; Console.WriteLine("The cost of " + BEST_CARPET + " is {0:C}", totalcost); Console.WriteLine( ); } } } carpetprice = 15.95; //per square yard totalcost = numofsquareyards * carpetprice; Console.WriteLine("The cost of " + ECONOMY_CARPET + " is " + "{0:C}", totalcost); Console.Read(); 81

82 Coding Standards C# Programming: From Problem Analysis to Program Design 82

83 Resources Naming Guidelines for.net Writing Readable Code C# Video tutorials Visual Studio 2012 C# 83

84 Chapter Summary C# Programming: From Problem Analysis to Program Design 84

85 Chapter Summary (continued) C# Programming: From Problem Analysis to Program Design 85

86 Chapter Summary (continued) Constants Assignment statements Order of operations Formatting output C# Programming: From Problem Analysis to Program Design 86

87 using System; using System.Globalization; using System.Resources; using System.Threading; Appendix 1 Formatting Numbers class Sample { public static void Main() { Console.WriteLine(String.Format("{0:0.00}", )); // Console.WriteLine(String.Format("{0:0.00}", 1.2)); // 1.20 Console.WriteLine(String.Format("{0:0.00}", 0.1)); // 0.10 Console.WriteLine(String.Format("{0:0.00}", 123.0)); // Console.WriteLine(String.Format("{0:0.00}", 123)); // Console.WriteLine(String.Format("{0:00.0}", ) ); // Console.WriteLine(String.Format("{0:00.0}", 1.99) ); // 02.0 Console.WriteLine(String.Format("{0:0,0.0}", )); // 12,345.7 Console.WriteLine(String.Format("{0:#.00}", 0.1) ); //.10 Console.WriteLine(String.Format("{0,10:0.0}", )); // Console.WriteLine(String.Format("{0,-10:0.0}", )); // Console.WriteLine(String.Format("Balance is ${0,-10:0.0}USD", )); // Balance is $123.5 USD Console.WriteLine(String.Format("{0:Balance is $0.0 USD}", )); // Balance is $123.5 USD Console.WriteLine(String.Format("{0:00000}", 123) ); // Console.WriteLine(String.Format("{0,5}", 123) ); // 123 Console.WriteLine(String.Format("{0,-5}", 123)); // 123 Console.WriteLine(String.Format("{0:(###) ###-####}", )); // (216) Console.WriteLine(String.Format("{0:(000) }", )); // (216) double decnum = 1.23; string strusa = decnum.tostring(cultureinfo.invariantculture.numberformat); // "1.23" string streurope = decnum.tostring(cultureinfo.getcultureinfo("es-es").numberformat); // "1,23" Console.WriteLine(strUSA ); // "1.23" Console.WriteLine(strEurope ); // "1,23" Console.ReadKey(); } } 87

88 using System; using System.Globalization; using System.Resources; using System.Threading; Appendix 2 Formatting Dates class DemoFormatDates { public static void Main() { //using other Culture values. See Link: // //Thread.CurrentThread.CurrentCulture = new CultureInfo("es-VE"); //Thread.CurrentThread.CurrentCulture = new CultureInfo("en-UK"); //Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US"); //Thread.CurrentThread.CurrentCulture = new CultureInfo("el-GR"); CultureInfo ci = Thread.CurrentThread.CurrentCulture; Console.WriteLine(ci); // en-us DateTime dt = DateTime.Now; Console.WriteLine(dt); // 8 / 8 / :39:58 PM Console.WriteLine(String.Format("{0:y yy yyy yyyy}", dt)); // Console.WriteLine(String.Format("{0:M MM MMM MMMM}", dt)); // 8 08 Aug August Console.WriteLine(String.Format("{0:d dd ddd dddd}", dt)); // 8 08 Sat Saturday Console.WriteLine(String.Format("{0:h hh H HH}", dt)); // hour 12/24 Console.WriteLine(String.Format("{0:m mm}", dt)); // minutes Console.WriteLine(String.Format("{0:s ss}", dt)); // seconds Console.WriteLine(String.Format("{0:t tt}", dt)); // P PM A.M. or P.M. Console.WriteLine(String.Format("{0:z zz zzz}", dt)); // :00 time zone Console.ReadKey(); } } C# Programming: From Problem Analysis to Program Design 88

89 using System; using System.Globalization; using System.Resources; using System.Threading; Appendix 3 Formatting Dates class Sample { public static void Main() { DateTime dt = DateTime.Now; Console.WriteLine(dt); // 8 / 8 / :22:15 PM Console.WriteLine(String.Format("{0:t}", dt)); // 10:22 PM Console.WriteLine(String.Format("{0:T}", dt)); // 10:22:15 PM Console.WriteLine(String.Format("{0:d}", dt)); // 8 / 8 / 2015 Console.WriteLine(String.Format("{0:D}", dt)); // Saturday, August 08, 2015 ShortTime LongTime ShortDate LongDate Console.WriteLine(String.Format("{0:F}", dt)); // Saturday, August 08, :22:15 PM FullDateTime Console.WriteLine(String.Format("{0:r}", dt)); // Sat, 08 Aug :22:15 GMT Console.WriteLine(String.Format("{0:u}", dt)); // :22:15Z RFC1123 UniversalSortableDate Console.ReadKey(); } } C# Programming: From Problem Analysis to Program Design 89

90 using System; using System.Globalization; using System.Resources; using System.Threading; Appendix 4 Formatting Tables class Sample { public static void Main() { Console.WriteLine("First Name Last Name Age "); Console.WriteLine(" ===============+-----"); Console.WriteLine(String.Format("{0,-10} {1,-15} {2,5}", "Daenerys", "Targaryen", 19)); Console.WriteLine(String.Format("{0,-10} {1,-15} {2,5}", "Drogon", "", 3)); Console.WriteLine(String.Format("{0,-10} {1,-15} {2,5}", "Maester", "Aemon", 102)); Console.WriteLine(" ===============+-----"); Console.ReadKey(); } } 90