C# Programming: From Problem Analysis to Program Design1 3 Data Types and Expressions C# Programming: From Problem Analysis to Program Design 2 nd Edition

C# Programming: From Problem Analysis to Program Design2 Chapter Objectives Declare memory locations for data Explore the relationship between classes, objects, and types Use predefined data types Use integral data types Use floating-point types Learn about the decimal data type Declare Boolean variables

C# Programming: From Problem Analysis to Program Design3 Chapter Objectives ( continued ) Declare and manipulate strings Work with constants Write assignment statements using arithmetic operators Learn about the order of operations Learn special formatting rules for currency Work through a programming example that illustrates the chapter’s concepts

C# Programming: From Problem Analysis to Program Design4 Memory Locations for Data Identifier –Name –Rules for creating an identifier Combination of alphabetic characters (a-z and A-Z), numeric digits (0-9), and the underscore First character in the name may not be numeric No embedded spaces – concatenate (append) words together Keywords cannot be used Use the case of the character to your advantage Be descriptive with meaningful names

C# Programming: From Problem Analysis to Program Design p.855 Reserved Words in C#

C# Programming: From Problem Analysis to Program Design6 Reserved Words in C# ( continued ) Contextual keywords New with C# 2.0 standards – November 2005 As powerful as regular keywords Contextual keywords have special meaning only when used in a specific context; other times they can be used as identifiers

C# Programming: From Problem Analysis to Program Design7 Naming Conventions Pascal case –First letter of each word capitalized –Class, method, namespace, and properties identifiers Camel case –Hungarian notation –First letter of identifier lowercase; first letter of subsequent concatenated words capitalized –Variables and objects

C# Programming: From Problem Analysis to Program Design8 Naming Conventions ( continued ) Uppercase –Every character is uppercase –Constant literals and for identifiers that consist of two or fewer letters

C# Programming: From Problem Analysis to Program Design9 Examples of Valid Names (Identifiers)

C# Programming: From Problem Analysis to Program Design10 Examples of Invalid Names (Identifiers)

C# Programming: From Problem Analysis to Program Design11 Variables Area in computer memory where a value of a particular data type can be stored –Declare a variable –Allocate memory Syntax –type identifier; Compile-time initialization –Initialize a variable when it is declared Syntax –type identifier = expression;

C# Programming: From Problem Analysis to Program Design12 Types, Classes, and Objects Type –C# has more than one type of number –int type is a whole number –floating-point types can have a fractional portion Types are actually implemented through classes –One-to-one correspondence between a class and a type –Simple data type such as int, implemented as a class

C# Programming: From Problem Analysis to Program Design13 Types, Classes, and Objects Instance of a class → object A class includes more than just data Encapsulation → packaging of data and behaviors into a single or unit→class

C# Programming: From Problem Analysis to Program Design14 Type, Class, and Object Examples

C# Programming: From Problem Analysis to Program Design15 Predefined Data Types Common Type System (CTS) Divided into two major categories Figure 3-1.NET common types

C# Programming: From Problem Analysis to Program Design16 Value and Reference Types Figure 3-2 Memory representation for value and reference types

C# Programming: From Problem Analysis to Program Design17 Value Types Fundamental or primitive data types Figure 3-3 Value type hierarchy

C# Programming: From Problem Analysis to Program Design18 Value Types ( continued )

C# Programming: From Problem Analysis to Program Design19 Integral Data Types Primary difference –How much storage is needed –Whether a negative value can be stored

C# Programming: From Problem Analysis to Program Design20 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

C# Programming: From Problem Analysis to Program Design21 Floating-point Types May be in scientific notation with an exponent n.ne±P –3.2e+5 is equivalent to 320,000 –1.76e-3 is equivalent to OR in standard decimal notation Default type is double

C# Programming: From Problem Analysis to Program Design22 Examples of Floating-point Declarations double extraPerson = 3.50; // extraPerson originally set // to 3.50 double averageScore = 70.0; // averageScore originally set // to 70.0 double priceOfTicket; // cost of a movie ticket double gradePointAverage; // grade point average float totalAmount = 23.57f; // note the f must be placed after // the value for float types

C# Programming: From Problem Analysis to Program Design23 Decimal Types Examples decimal endowmentAmount = M; decimal deficit; Monetary data items As with the float, must attach the suffix ‘m’ or ‘M’ onto the end of a number to indicate decimal –Float attach ‘f’ or “F’

C# Programming: From Problem Analysis to Program Design24 Boolean Variables Based on true/false, on/off logic Boolean type in C# → bool Does not accept integer values such as 0, 1, or -1 bool undergraduateStudent; bool moreData = true;

C# Programming: From Problem Analysis to Program Design25 Strings Reference type Represents a string of Unicode characters string studentName; string courseName = “Programming I”; string twoLines = “Line1\nLine2”;

C# Programming: From Problem Analysis to Program Design26 Making Data Constant Add the keyword const to a declaration Value cannot be changed Standard naming convention Syntax –const type identifier = expression; const double TAX_RATE = ; const int SPEED = 70; const char HIGHEST_GRADE = ‘A’;

C# Programming: From Problem Analysis to Program Design27 Assignment Statements Used to change the value of the variable –Assignment operator (=) Syntax variable = expression; Expression can be: –Another variable –Compatible literal value –Mathematical equation –Call to a method that returns a compatible value –Combination of one or more items in this list

C# Programming: From Problem Analysis to Program Design28 Examples of Assignment Statements int numberOfMinutes, count, minIntValue; char firstInitial, yearInSchool, punctuation; numberOfMinutes = 45; count = 0; minIntValue = ; firstInitial = ‘B’; yearInSchool = ‘1’; enterKey = ‘\n’;// newline escape character

C# Programming: From Problem Analysis to Program Design29 Examples of Assignment Statements ( continued ) double accountBalance, weight; decimal amountOwed, deficitValue; bool isFinished; accountBalance = ; weight = 1.7E-3; //scientific notation may be used amountOwed = m; // m or M must be suffixed to // decimal deficitValue = M;

C# Programming: From Problem Analysis to Program Design30 Examples of Assignment Statements ( continued ) int count = 0, newValue = 25; string aSaying, fileLocation; aSaying = “First day of the rest of your life!\n "; fileLocation isFinished = false;// declared previously as a bool count = placed before a string literal signals that the characters inside the double quotation marks should be interpreted verbatim

C# Programming: From Problem Analysis to Program Design31 Examples of Assignment Statements ( continued ) Figure 3-5 Impact of assignment statement

C# Programming: From Problem Analysis to Program Design32 Arithmetic Operations Simplest form of an assignment statement resultVariable = operand1 operator operand2; Readability –Space before and after every operator

C# Programming: From Problem Analysis to Program Design33 Basic Arithmetic Operations Modulus operator with negative values –Sign of the dividend determines the result –-3 % 5 = -3; 5 % -3 = 2; -5 % -3 = -2; Figure 3-6 Result of 67 % 3

C# Programming: From Problem Analysis to Program Design34 Basic Arithmetic Operations ( continued ) Plus (+) with string Identifiers –Concatenates operand2 onto end of operand1 string result; string fullName; string firstName = “Rochelle”; string lastName = “Howard”; fullName = firstName + “ “ + lastName;

C# Programming: From Problem Analysis to Program Design35 Concatenation Figure 3-7 String concatenation

C# Programming: From Problem Analysis to Program Design36 Basic Arithmetic Operations ( continued ) Increment and Decrement Operations –Unary operator num++; // num = num + 1; --value1; // value = value – 1; –Preincrement/predecrement versus post int num = 100; System.Console.WriteLine(num++); // Displays 100 System.Console.WriteLine(num); // Display 101 System.Console.WriteLine(++num); // Displays 102

C# Programming: From Problem Analysis to Program Design37 Basic Arithmetic Operations ( continued ) int x = 100; System.Console.WriteLine(x++ + “ “ + ++x); // Displays Figure 3-9 Change in memory after count++; statement executed

C# Programming: From Problem Analysis to Program Design38 Basic Arithmetic Operations ( continued ) Figure 3-10 Results after statement is executed

C# Programming: From Problem Analysis to Program Design39 Compound Operations Accumulation –+=

C# Programming: From Problem Analysis to Program Design40 Basic Arithmetic Operations ( continued ) Order of operations –Order in which the calculations are performed Example –answer = 100; –answer += 50 * 3 / 25 – 4; 50 * 3 = / 25 = 6 6 – 4 = = 102

C# Programming: From Problem Analysis to Program Design41 Order of Operations Associativity of operators –Left –Right

C# Programming: From Problem Analysis to Program Design42 Order of Operations ( continued ) Figure 3-11 Order of execution of the operators

C# Programming: From Problem Analysis to Program Design43 Mixed Expressions Implicit type coercion –Changes int data type into a double –No implicit conversion from double to int Figure 3-12 Syntax error generated for assigning a double to an int

C# Programming: From Problem Analysis to Program Design44 Mixed Expressions ( continued ) Explicit type coercion –Cast –(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 = 75.0

C# Programming: From Problem Analysis to Program Design45 Formatting Output You can format data by adding dollar signs, percent symbols, and/or commas to separate digits You can suppress leading zeros You can pad a value with special characters –Place characters to the left or right of the significant digits Use format specifiers

C# Programming: From Problem Analysis to Program Design46 Numeric Format Specifiers

C# Programming: From Problem Analysis to Program Design47 Numeric Format Specifiers ( continued )

C# Programming: From Problem Analysis to Program Design48 Custom Numeric Format Specifiers

C# Programming: From Problem Analysis to Program Design49 Custom Numeric Format Specifiers ( continued )

C# Programming: From Problem Analysis to Program Design50 Formatting Output

C# Programming: From Problem Analysis to Program Design51 Programming Example – CarpetCalculator Figure 3-13 Problem specification sheet for the CarpetCalculator example

C# Programming: From Problem Analysis to Program Design52 Data Needs for the CarpetCalculator

C# Programming: From Problem Analysis to Program Design53 Non-changing Definitions for the CarpetCalculator

C# Programming: From Problem Analysis to Program Design54 CarpetCalculator Example Figure 3-14 Prototype for the CarpetCalculator example

C# Programming: From Problem Analysis to Program Design55 Algorithm for CarpetCalculator Example Figure 3-15 CarpetCalculator flowchart

C# Programming: From Problem Analysis to Program Design56 Algorithm for the CarpetCalculator Example ( continued ) Figure 3-16 Structured English for the CarpetCalculator example

C# Programming: From Problem Analysis to Program Design57 CarpetCalculator Example ( continued ) Figure 3-17 Class diagram for the CarpetCalculator example

C# Programming: From Problem Analysis to Program Design58 /* CarpetCalculator.csAuthor: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;

C# Programming: From Problem Analysis to Program Design59 roomLength = roomLengthFeet + roomLengthInches / INCHES_PER_FOOT; roomWidth = roomWidthFeet + roomWidthInches / INCHES_PER_FOOT; numOfSquareFeet = roomLength * roomWidth; numOfSquareYards = numOfSquareFeet / SQ_FT_PER_SQ_YARD; carpetPrice = 27.95; totalCost = numOfSquareYards * carpetPrice; Console.Out.WriteLine("The cost of " + BEST_CARPET + " is {0:C}", totalCost); Console.Out.WriteLine( ); carpetPrice = 15.95; totalCost = numOfSquareYards * carpetPrice; Console.Out.WriteLine("The cost of " + ECONOMY_CARPET + " is " + "{0:C}",totalCost); Console.Read(); } } }

C# Programming: From Problem Analysis to Program Design60 CarpetCalculator Example ( continued ) Figure 3-18 Output from the CarpetCalculator program

C# Programming: From Problem Analysis to Program Design61 Chapter Summary Memory locations for data Relationship between classes, objects, and types Predefined data types –Integral data types –Floating-point types –Decimal type –Boolean variables –Strings

C# Programming: From Problem Analysis to Program Design62 Chapter Summary ( continued ) Constants Assignment statements –Order of operations Formatting output