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1 C++ FOR ENGINEERS AND SCIENTISTS THIRD EDITION Chapter 2 Problem Solving Using C++ 1

2 Objectives 目標 2 In this chapter, you will learn about: Modular programs 模組化程式 Programming style 寫程式的風格 Data types 資料種類 Arithmetic operations 數學運算 Variables and declaration statements 變數和宣告敘述 Common programming errors 常見程式錯誤

3 Introduction to C++ 3 Modular program: A program consisting of interrelated segments arranged in a logical and understandable form 模組化程式 Easier to develop, correct, and modify than other kinds of programs 容易開發更正和修改 Module: A small segment which is designed to perform a specific task 模組 : 完成特定工作的單元 A group of modules is used to construct a modular program 一群模組形成模組化程式

4 Introduction to C++ (continued) 4 Figure 2.1 A well-designed program is built using modules. 一個設計良好的程式是由模組構成的

5 Introduction to C++ (continued) 5 Modules in C++ can be classes or functions 模組可以是類別或函數 Function: Accepts an input and produces an output by processing the input in some fashion 函數 : 接收輸入資料加以處理然後產生結果 A function s processing is encapsulated and hidden within the function 函數的處理功能封裝在函數中

6 Introduction to C++ (continued) 6 Figure 2.2 A multiplying function. 一個相乘的函數

7 Introduction to C++ (continued) 7 Class: Contains both data and functions used to manipulate the data 類別包含資料和函數 Function: Encapsulates a set of operations 函數 : 包含一組運算方式 A class encapsulates data plus one or more sets of operations 類別包含資料和資料的運算方式 Identifier: A name given to an element of the language, such as a class or function 識別字 : 給予類別或函數的名字

8 Introduction to C++ (continued) 8 Rules for forming identifier names: 取名規則 First character must be a letter or underscore 第一個字元必須是英文字母或底線 Only letters, digits, or underscores may follow the initial letter (no blanks allowed) 其後可用字母數字或底線, 但不能有空格 Keywords cannot be used as identifiers 不可使用關鍵字 Maximum length of an identifier = 1024 characters 識別字最長可達 1024 個字元

9 Introduction to C++ (continued) 9 Keyword: A reserved name that represents a built-in object or function of the language 關鍵字 :C++ 內建的保留字 Table 2.1: Keywords in C++ 關鍵字

10 Introduction to C++ (continued) 10 Examples of valid C++ identifiers: 識別字範例 degtorad intersect addnums slope bessell multtwo findmax density Examples of invalid C++ identifiers: 無效識別字範例 1AB3 (begins with a number) 由數字開始 E*6 (contains a special character) 有特殊符號 while (this is a keyword) 保留字

11 Introduction to C++ (continued) 11 Function names 函數名稱 Require a set of parentheses at the end 字尾需要括號 Can use mixed upper and lower case 可以大小寫混合 Should be meaningful, or be a mnemonic 幫助記憶的較佳 Mnemonic: A word designed as a memory aid 助記符號 Examples of function names: 函數名稱範例 easy() c3po() r2d2() theforce() Note that C++ is a case-sensitive language! 在 C++ 中大小寫不同

12 The main() Function 主函數 12 Overall structure of a C++ program contains one function named main(), called the driver function 一個 C++ 程式包含一個 main(), 又稱驅動函數 All other functions are invoked from main() 其他函數都由 main() 呼叫

13 The main() Function (continued) 13 Figure 2.3 The main() function directs all other functions. 主函數指揮其他函數

14 The main() Function (continued) 14 Function header line: First line of a function, which contains: 函數標題行 ( 函數的第一行 ) The type of data returned by the function (if any) 回傳資料型態 The name of the function 函數名稱 The type of data that must be passed into the function when it is invoked (if any) 需要傳給函數的資料種類 Arguments: The data passed into a function 引數 : 傳給函數的資料 Function body: The statements inside a function (enclosed in braces) 函數主體 ( 在大括號之間 )

15 The main() Function (continued) 15 Each statement inside the function must be terminated with a semicolon 每一敘述結尾需有分號 return: A keyword causing the appropriate value to be returned from the function 函數回傳的關鍵字是 return The statement return 0 in the main() function causes the program to end 主函數中回傳 0 表示程式成功結束

16 The main() Function (continued) Figure 2.4 The structure of a main() function 主程式 main() 的架構 16

17 The cout Object 輸出物件 17 cout object: An output object that sends data to a standard output display device 使用 cout 物件列印到螢幕

18 The cout Object (continued) 18 Preprocessor command: Starts with a # 預處理指令以 # 開始 Causes an action before the source code is compiled into machine code 在編譯原始碼前產生動作 #include <file name>: Causes the named file to be inserted into the source code 包含檔案指令讓指定檔案插入原始碼中 C++ provides a standard library with many pre-written classes that can be included 由 C++ 的函式庫提供許多預先寫好的類別 Header files: Files included at the head (top) of a C++ program 標頭檔案 : 在 C++ 程式開頭包含的檔案

19 The cout Object (continued) 19 using namespace <namespace name> : Indicates where header file is located 指示標頭檔案放在哪裡 Namespaces qualify a name 使用 Namespaces 指定名稱 A function name in your class can be the same as one used in a standard library class 在你的類別中的函數名稱可以和標準函數類別中的相同 String: Any combination of letters, numbers, and special characters enclosed in double quotes (a delimiter) 字串 : 一連串包在雙引號中的字母數字和特殊符號 Delimiter: A symbol that marks the beginning and ending of a string; not part of the string 定義符號 : 標示字串開頭和結尾的符號

20 The cout Object (continued) 20

21 The cout Object (continued) 21 Escape sequence: One or more characters preceded by a backslash, \ 跳脫程序 : 加上反斜線的一個或多個字元

22 Programming Style 程式風格 22 Although more than one C++ statement can be on a single line, good style calls for one statement per line 一個敘述一行是較好的風格 Opening and closing braces {} for the function body should each be on separate lines 左右大括號各自一行 Statements in the function body should be indented 函數內的敘述應該向右縮排

23 Comments 註解 23 Comments: Explanatory remarks in the source code added by the programmer 註解是原始碼中的說明 Line comment: Begins with // and continues to the end of the line 單行式註解由 // 開始 Line comment can be on a line by itself, or at the end of a line of code 放在單獨一行或在一行敘述的結尾 Line comment cannot be longer than one line 不能長於一行

24 Comments (continued) 24

25 Comments (continued) 25 Block comments: Span across two or more lines 區塊註解 : 可以有多行 Begin with /* and ends with */ 開始和結尾的符號 Example: 範例 /* This is a block comment that spans across three lines */

26 Data Types 資料種類 26 Data type: A set of values and the operations that can be applied to these values 資料種類 : 一組資料和可以用於資料的運算方式 Two fundamental C++ data groupings: 兩種 C++ 資料 Class data type (a class): Created by the programmer 類別資料型態 : 由程式設計師制定 Built-in data type (primitive type): Part of the C++ compiler 內建資料型態

27 Data Types (continued) 資料種類 27 整數實數 Figure 2.5 Built-in data types 內建資料種類

28 Data Types (continued) 28 Table 2.2 Built-in Data Types Operations 內建資料種類運算方式

29 Data Types (continued) 29 Literal (constant): An actual value 常數 Examples: 範例 3.6 //numeric literal Hello //string literal Integer: A whole number 整數 C++ has nine built-in integer data types 九種不同的整數型態 Each provides differing amounts of storage (compiler dependent) 差別在儲存空間 ( 視編譯器而定 )

30 Integer Data Types 整數資料種類 30 Figure 2.6 C++ integer data types 整數資料種類

31 Integer Data Types (continued) 31 int data type: Whole numbers, optionally with plus (+) or minus ( ) sign 整數型態 ( 有正負號 ) Example: 2 char data type: Individual character; any letter, digit, or special character enclosed in single quotes 字元資料型態 : 單引號中的字母數字特殊符號 Example: A 注意 : 字元也是整數型態 Character values are usually stored in ASCII code 字元通常以 ASCII 碼儲存

32 Integer Data Types (continued) 32 Table 2.3 The ASCII Uppercase Letter Codes 在 ASCII 中的大寫字母編碼

33 Integer Data Types (continued) 33 When storing the ASCII codes shown in Table 2.3 to represent text, each letter takes one byte of memory and is represented by the associated number from the chart 一個字元佔用一個位元組的記憶體 Figure 2.7 The letters BARTER stored inside a computer 電腦中儲存 BARTER 的方式

34 Integer Data Types (continued) 34 Escape character: The backslash, \ 跳脫字元 Indicates an escape sequence 表示跳脫程序 Escape sequence: Tells compiler to treat the following characters as special instruction codes 跳脫程序告訴編譯器將下一個符號視為指令碼

35 Integer Data Types (continued) 35 Table 2.4 Escape sequences 跳脫序列

36 Integer Data Types (continued) 36 Table 2.4 Escape sequences (continued) 跳脫序列

37 Integer Data Types (continued) 37 bool data type: Represents Boolean (logical) data 邏輯資料型態 Restricted to two values: true or false 只有真或假 Useful to indicate a condition and take a prescribed course of action 用來決定情況與執行預定的動作

38 Determining Storage Size 決定儲存大小 38 A unique feature of C++ is that you can see where and how values are stored 特殊的 C++ 功能讓你知道資料如何儲存 sizeof() operator provides the number of bytes used to store values of the data type names in the parenthesis 使用 sizeof() 提供儲存資料所需的位元數 Values returned by sizeof() are compiler dependent 每個編譯器的結果可能不同

39 Determining Storage Size 39 (continued)

40 Signed and Unsigned Data Types 40 有正負和無正負的資料型態 Signed data type: One that permits negative, positive, and zero values 有正負的資料型態 Unsigned data type: Permits only positive and zero values 無正負的資料型態 ( 只允許 0 和正數 ) An unsigned data type provides essentially double the range of its signed counterpart 無正負的資料儲存範圍通常是有正負的兩倍

41 Signed and Unsigned Data Types 41 (continued) Table 2.5 Integer Data Type Storage 整數資料儲存範圍

42 Floating-Point Types 浮點資料型態 42 Floating-point number (real number): Zero or any positive or negative number containing a decimal point 浮點數 ( 實數 ) Examples: No special characters are allowed 不允許特殊符號 Three floating-point data types in C++: 三種浮點數 float (single precision) 單精準度 double (double precision) 雙精準度 long double

43 Floating-Point Types (continued) 43 Table 2.6 Floating-Point Data Types 浮點數資料儲存範圍

44 Floating-Point Types (continued) 44 float literal: Append an f or F to the number 字面上的浮點數 ( 加上 f 或 F) long double literal: Append an l or L to the number 字面上的長浮點數 ( 加上 l 或 L) Examples: // a double literal 9.234F // a float literal 9.234L // a long double literal

45 Arithmetic Operations 算數運算 45 C++ supports addition, subtraction, multiplication, division, and modulus division 支援加減乘除和 modulus Different data types can be used in the same arithmetic expression 同一算式中可以使用不同的資料型態 Arithmetic operators are binary operators 算術運算子是二元運算子 Binary operators: Require two operands 二元運算子需要兩個操作單元

46 Arithmetic Operations (continued) 46 Operation Addition Subtraction Multiplication Division Modulus division Operator + - * / %

47 Arithmetic Operations (continued) 47

48 Expression Types 運算式種類 48 Expression: Any combination of operators and operands that can be evaluated to yield a value 運算式 : 運算元件和運算符號的組合, 可產生一個結果 If all operands are the same data type, the expression is named by the data type used (integer expression, floatingpoint expression, etc.) 如果所有的運算元件都是相同的資料型態, 那麼運算式用該資料型態來稱呼 Mixed-mode expression: Contains integer and floating-point operands 混合運算式 ( 有整數和實數 ) Yields a double-precision value 產生雙精準度的值

49 Integer Division 整數除法 49 Integer division: Yields an integer result 產生整數 Any fractional remainders are dropped (truncated) 任何除不盡的部份加以捨棄 Example: 15/2 yields 7 Modulus (remainder) operator: Returns only the remainder 產生餘數 Example: 9 % 4 yields 1

50 Negation 否定 50 Unary operator: Requires only one operand 一元運算子 Negation operator (-): Reverses the sign of the number 改變正負號

51 Operator Precedence and 51 Associativity 運算符號優先順序 Rules for writing arithmetic expressions: 規則 Never place two consecutive binary arithmetic operators side by side 不可把兩個運算符號放在一起 Use parentheses to form groupings 使用括號 Contents within parentheses are evaluated first 括號內先做 May nest parentheses within other parentheses 括號內可以再有括號 Evaluated from innermost to outermost 從最裡面算起 Use the * operator for multiplication, not parentheses 乘號要寫出

52 Operator Precedence and 52 Associativity (continued) Expressions with multiple operators are evaluated by precedence of operators: 有多個運算符號的算式時看優先順序 All negations occur first 先做負號 Multiplication, division, and modulus are next, from left to right 其次是乘除求餘數 ( 左到右 ) Addition and subtraction are last, from left to right 最後是加減 ( 左到右 )

53 Operator Precedence and 53 Associativity (continued) Associativity: the order in which operators of the same precedence are evaluated 關聯性 : 當運算符號同等優先時的運算順序 Table 2.8 Operator Precedence and Associativity

54 Variables and Declaration 54 Statements 變數和宣告敘述 Variable: All integer, float-point, and other values used in a program are stored and retrieved from the computer s memory 變數儲存在記憶體中 Each memory location has a unique address 每一個記憶體位置有獨特的地址 Figure 2.8 Enough storage for two integers

55 Variables and Declaration 55 Statements (continued) Variable: Symbolic identifier for a memory address where data can be held 變數 Use identifier naming rules for variable names 變數的命名原則與識別字相同 Figure 2.9 Naming storage locations

56 Variables and Declaration 56 Statements (continued) Assignment statement: Used to store a value into a variable 指定敘述 ( 用來將數值存到變數中 ) Value of the expression on the right side of the = is assigned to the memory location of the variable on the left side of the = 等號右邊的運算結果存到等號左邊的變數中 Examples: num1 = 45; num2 = 12; total = num1 + num2;

57 Variables and Declaration 57 Statements (continued) Declaration statement: Specifies the data type and identifier of a variable; sets up the memory location 宣告敘述 : 指定資料種類並設定儲存空間 Syntax: datatype variablename; 語法 Data type is any valid C++ data type 資料種類可以是任何 C++ 認可的型態 Example: int sum; Declarations may be used anywhere in a function 宣告敘述可用在函數中任何地方 Usually grouped at the opening brace 通常放在開頭

58 Variables and Declaration 58 Statements (continued) Character variables: Declared using the char keyword 字元變數 : 使用 char 宣告 Multiple variables of the same data type can be declared in a single declaration statement 多個變數可以在同一行宣告 Example: double grade1, grade2, total, average; Variables can be initialized in a declaration 變數可以起始化 Example: double grade1 = 87.0 A variable must be declared before it is used 變數在使用前必須先宣告

59 Variables and Declaration 59 Statements (continued)

60 Memory Allocation 記憶體配置 60 Definition statement: A declaration that defines how much memory is needed for data storage 宣告定義需要多少記憶體儲存資料 Three items associated with each variable: 三項有關的東西 Data type 資料種類 Actual value stored in the variable (its contents) 資料內容 Memory address of the variable 變數記憶體位置 Address operator (&) provides the variable s address 地址運算符號

61 Memory Allocation (continued) 61 Declaring a variable causes memory to be allocated based on the data type 宣告變數使記憶體分配所需的空間 Figure 2.10b Defining the floating-point variable named slope

62 Memory Allocation (continued) 62

63 A Case Study: Radar Speed Traps 63 案例分析 Step 1: Analyze the Problem 分析問題 Understand the desired outputs 了解所需輸出 Determine the required inputs 決定所需輸入 Step 2: Develop a Solution 提出解決方法 Determine the algorithms to be used 決定運算法 Use top-down approach to design 使用從上而下的方式 Step 3: Code the Solution 撰寫程式 Step 4: Test and Correct the Program 測試程式

64 A Case Study: Radar Speed Trap 64 (continued) Analyze the Problem 分析問題 Output: Speed of the car 輸出 : 車速 Inputs: Emitted frequency and received frequency 輸入 : 發出和接收頻率 Develop a Solution 發展解法 Algorithm: 運算法 Assign values to f0 and f1 指定數值給 f0 和 f1 Calculate and display speed 計算和顯示速度

65 A Case Study: Radar Speed Trap 65 (continued) Code the Solution

66 A Case Study: Radar Speed Trap 66 (continued) Test and Correct the Program 測試和修正程式 Verify that the calculation and displayed value agree with the previous hand calculation 驗證計算結果和手算相同 Use the program with different values of received frequencies 使用程式計算不同接收頻率

67 Common Programming Errors 常見 67 錯誤 Omitting the parentheses after main() 忘記括號 Omitting or incorrectly typing the opening brace, {, or the closing brace, }, that signifies the start and end of a function body 打錯開始和結束的大括號 Misspelling the name of an object or function 拼字錯誤 Forgetting to enclose a string sent to cout with quotation marks 忘記使用雙引號輸出字串 Omitting a semicolon at end of statement 忘記分號

68 Common Programming Errors 68 (continued) Adding a semicolon at end of #include statement 在 #include 後面加上分號 Missing \n to indicate new line 忘記換行符號 Substituting letter O for zero and vice versa 弄混字母 O 和數字 0 Failing to declare all variables 忘記宣告變數

69 Common Programming Errors 69 (continued) Storing an incorrect data type into a variable 將錯誤資料型態儲存到變數中 Attempting to use a variable with no value 使用沒有資料的變數 Dividing integer values incorrectly 錯誤的整數相除 Mixing data types in the same expression

70 Summary 70 A C++ program consists one or more modules, called functions, one of which must be called main() 每一個 C++ 程式都有一個以上的模組, 其中一個必定是 main() All C++ statements must be terminated by a semicolon 每一行敘述結尾要有分號 Data types include int, float, bool, char 資料種類 cout object can be used to display data 使用 cout 物件輸出 cout object requires the preprocessor command #include <iostream> 使用 cout 物件須有 #include <iostream>

71 Summary (continued) 71 Variables must be declared with their data type 變數必須先宣告 A variable can be used only after it has been declared 變數需要先宣告才能使用 Variables may be initialized when declared 變數可以賦予起始值 Definition statement causes computer to allocate memory for a variable 定義敘述使電腦分配記憶體給變數 sizeof() operator yields the amount of storage reserved for a variable 用此函數求得分配給變數的記憶體量

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