1. Lecture 4: Computer Languages. A Tutorial Introduction to C++ COS120 Software Development Using C++ AUBG, COS dept

2. 2 Lecture Contents: t Programming languages (Reminder, may skip); t Processing HLL program (Reminder, may skip); –(Editing, Compiling, Linking, Loading, Running) t The C++ Programming Language –A tutorial introduction.

3. 3 Programming Languages t Machine Language –“Native tongue” of the computer –Binary 0s and 1s that specify what to do 0010 0000 0000 0100 1000 0000 0000 0101 0011 0000 0000 0110 t High - Level Languages –Resemble human language (C++, C, Pascal) cost = price + tax;

4. 4 Processing a High-Level Language Program t Set of programs used to develop software encapsulated within a software package, IDE t Text editor t Compiler t Linker t Loader t Examples: MS Visual Studio, Code::Blocks, g++.

5. 5 Processing a Program t Editor used to enter the source program –Output saved as a source file ( prog.c or prog.cpp ) t Compiler translates the source program –Displays syntax errors (not descriptive) –Generates an object program ( prog.obj ) t Linker combines object file with other object files –Generates an executable program ( prog.exe ) t Loader loads executable program into RAM t Program execution starts t Program execution terminates

6. 6 Process Cycle

7. 7 Tutorial Introduction to C++ t Logical Structure of a program – C++ program consists of –functions and –global variables. t Functions are separate program units and contain statements that specify computing operations to be done. t Variables store values used during computation. t Variables are named by the developer.  Functions are named by the developer except one that is always present and named main().

8. 8 Tutorial Introduction to C++  Program as Top-Down hierarchy of syntax categories: –Program// Program has function(s) –Function(s)// Function has statement(s) –Statement(s)// Statement has expression(s) –Expression(s)// Expression has operator(s) and operand(s) –Operator(s) –Operand(s) –Data

9. 9 Tutorial Introduction to C++  Program as Bottom-Up hierarchy of syntax categories: –Program –Function(s)// Function(s) are part of a program –Statement(s)// Statement(s) are part of a function –Expression(s)// Expression(s) are part of a statement –Operator(s)// Operator(s) are part of an expression –Operand(s) // Operand(s) are part of an expression –Data

10. 10 Typical structure of an elementary program void main() { } Open next slide to look at the “Hello, World!” program

11. 11 The “Hello, World!” program C++ notation #include using namespace std; void main( ) { cout << “\nHello, World!”; }

12. 12 Tutorial Introduction to C++ t Names –strings of characters of any length –case sensitive –key words are reserved t Names, also called identifiers: –reserved words ( if, else, for, while, … ) –standard identifiers ( cin, cout, … ) –user defined identifiers ( Price, Pom12a, FileSize, Counter, Ion12bcd, … )

13. 13 Tutorial Introduction to C++ t Data – classification by category: –Literal Values –Named Constants –Variables

14. 14 Tutorial Introduction to C++ t Data – classification by type: –Boolean (keyword bool ) –Character (keyword char ) –Integer (keywords int, unsigned, short, long ) –Real (keywords float, double, long double )

15. 15 Tutorial Introduction to C++ t Operators: Survey on arithmetic, relational, logical and assignment operators. –Arithmetic*/% –+- –Relational >= –Equality==!= –Logical AND (conjunction) && –Logical OR (disjunction)|| –Assignment=

16. 16 Tutorial Introduction to C++ t Expressions - are composed of operands and operators; 1 + 2 A – 3 * 5.6 A = B + C A = B = 1 + 2 A = (B = C / (D*E)) + F; Attention: expression terminated by ; is a statement Attention: A program is a sequence of statements

17. 17 Tutorial Introduction to C++ t Executable statements: assignment = ; x = 5; How to read?“x becomes 5”or “x gets 5”or “x takes the value of 5”but never x equals 5 (NO!)

18. 18 Tutorial Introduction to C++ t Executable statements: selection/decision if ( ) if ( ) else switch statement

19. 19 Tutorial Introduction to C++ t Example: fragment of linear equation solution if ( ) if ( b != 0 ) x = -c/b; if ( b != 0 ) { x = -c/b; cout << “\n Solution is =“ << x; }

20. 20 Tutorial Introduction to C++ t Example: fragment of triangle area problem if ( ) else if ( a+b>c && b+c>a && a+c>b) { p = (a+b+c)/2; s = sqrt( p*(p-a)*(p-b)*(p-c) ); cout << “\n Area is = “ << s; } else cout << “\nYou entered invalid data“;

21. 21 Tutorial Introduction to C++ t Example: Fragment of menu choice program switch statement int choice; cin >> choice; switch (choice) { case 1:Rectangle();break; case 2:Square();break; case 3:Triangle();break; case 4:Circle();break; default:cout << “\n Invalid input”; };

22. 22 Tutorial Introduction to C++ t Executable statements: iteration/repetition –for ( ; ; ) –while ( ) –do while( ) ;

23. 23 Tutorial Introduction to C++ t Example: sum of first five integers s=1+2+3+4+5 –for ( ; ; ) int I, s=0; for ( I=1; I<=5; I++ ) { s = s + I; // display intermediate results cout << ‘\n’ << s; } // display final result cout << “\n\n\nFinal sum is = ” << s;

24. 24 Tutorial Introduction to C++ t Example: sum of first five integers s=1+2+3+4+5  while ( ) int I = 1, s; s=0; while ( I<=5 ) { s = s + I; // display intermediate results cout << ‘\n’ << s; I = I + 1; } // display final result cout << “\n\n\nFinal sum is = ” << s;

25. 25 Tutorial Introduction to C++ t Example: sum of first five integers s=1+2+3+4+5  do while( ) ; int I = 1; int s = 0; do { s = s + I; // display intermediate results cout << ‘\n’ << s; I = I + 1; } while (I<5); // display final result cout << “\n\n\nFinal sum is = ” << s;

26. 26 Tutorial Introduction to C++ Elementary standard input/output: t I/O - C notation based on library functions getchar(), putchar() - Read/Write a character gets(), puts() - Read/Write a string of chars scanf(), printf() - formatted Read/Write t I/O - C++ notation based on OO streams cin - standard input stream cout - standard output stream

27. 27 The “Hello, World!” program C notation #include void main( ) { printf(“\nHello, World!”); }

28. 28 The “Hello, World!” program C++ notation #include using namespace std; void main( ) { cout << “\nHello, World!”; }

29. 29 The “Hello, World!” program #include In C++, a stream is a sequence of characters associated with an input device, or an output device, or a disk file. Class iostream defines object cin as the stream associated with input device (keyboard). Class iostream defines object cout as the stream associated with output device (screen). Class iostream also defines: –input operator >> ( extract from input stream); –output operator << ( insert to output stream).

30. 30 The “Hello, World!” program Concrete form: using namespace std; Abstract form: using namespace ; This line indicates that the program uses objects defined in the namespace specified by in general (std for concrete). This line should always follow the #include-s.

31. 31 Before lecture end Lecture: A Tutorial Introduction to C++ More to read: Friedman/Koffman, Chapter 02 Or Coming approx. 60 slides

32. Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Chapter 2: Overview of C++ Problem Solving, Abstraction, and Design using C++ 5e by Frank L. Friedman and Elliot B. Koffman

33. 33 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley C++ Background Introduced by Bjarne Stroustrup of AT&T’s Bell Laboratories in mid-1980’s Based on C Supports object-oriented programming 1998 Standard

34. 34 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 2.1 C++ Language Elements Comments Compiler directives Function main Declaration statements Executable statements

35. 35 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Comments // symbols indicate a line comment - apply to just the rest of the line Block comments start with /* and end with */ - apply to as many lines as you like Used to describe the code in English or provide non-code information E.g. to include the name of the program or the author’s name

36. 36 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Listing 2.1 Converting miles to kilometers

37. 37 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley #include Compiler directive Includes previously written code from a library into your program E.g. #include has operators for performing input and output within the program Libraries allow for code reuse

38. 38 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley using namespace std; Indicates to compiler that this program uses objects defined by a standard namespace called std. Ends with a semicolon Follows #include directives in the code Must appear in all programs

39. 39 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Function main int main ( ) { // function body }

40. 40 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Function main Exactly one main function per program A function is a collection of related statements that perform a specific operation int indicates the return type of the function ( ) indicates no special information passed to the function by the operating system

41. 41 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Types of Statements Declaration statements - describe the data the function needs: const float KM_PER_MILE = 1.609; float miles, kms; Executable statements - specify the actions the program will take: cout << “Enter the distance in miles: “; cin >> miles;

42. 42 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 2.2 Reserved Words (Keywords) Have special meaning in C++ Cannot be used for other purposes

43. 43 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Table 2.1 Reserved words in Listing 2.1

44. 44 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Identifiers Names for data and objects to be manipulated by the program Must begin with a letter or underscore (not recommended) Consist only of letters, digits, and underscores Cannot be reserved word Upper and lower case significant

45. 45 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Identifiers Identifier Use cin C++ name for standard input stream cout C++ name for standard output stream km Data element for storing distance in kms KM_PER_MILE Conversion constant miles Data element for storing distance in miles std C++ name for the standard namespace

46. 46 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 2.3 Data Types Defines a set of values and operations that can be performed on those values integers –positive and negative whole numbers, e.g. 5, -52, 343222 –short, int, long –represented internally in binary –predefined constants INT_MIN and INT_MAX

47. 47 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Data Types (con’t) Floating point (real) –number has two parts, integral and fractional –e.g. 2.5, 3.66666666, -.000034, 5.0 –float, double, long double –stored internally in binary as mantissa and exponent –10.0 and 10 are stored differently in memory

48. 48 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Data Types (con’t) Boolean –named for George Boole –represent conditional values –values: true and false

49. 49 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Data Types (con’t) Characters –represent individual character values E.g. ’A’ ’a’ ’2’ ’*’ ’”’ ’ ’ –stored in 1 byte of memory –special characters: escape sequences E.g. ’\n’ ’\b’ ’\r’ ’\t’ ‘\’’

50. 50 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley string Class Strings not built-in, but come from library Classes extend C++ string literal enclosed in double quotes E.g.: “Enter speed: “ “ABC” “B” “true” “1234” #include –for using string identifiers, but not needed for literals

51. 51 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Variable Declarations Set aside memory with a specific name for the data and define its values and operations The value can change during execution type identifier-list; E.g.:float x, y; int me, you; float week = 40.0; string flower = “rose”;

52. 52 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Constant Declarations Memory cells whose values cannot change once set const type constant-identifier = value; E.g.: const float KM_PER_MILE = 1.609; Often identified by using all upper case name

53. 53 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Listing 2.2 Printing a welcoming message

54. 54 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 2.4 Executable Statements Assignment statements Input statements Program output The return statement

55. 55 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Figure 2.2 Memory (a) before and (b) after execution of a program

56. 56 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Assignment Statements variable = expression; E.g.: kms = KM_PER_MILE * miles;

57. 57 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Input Statements Obtain data for program to use - different each time program executes Standard stream library iostream cin - name of stream associated with standard input device (keyboard by default) Extraction operator (>>) E.g.: cin >> miles; cin >> age >> firstInitial;

58. 58 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley In Listing 2.2: cin >> letter1 >> letter2 >> lastname; has the effect:

59. 59 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Figure 2.6 Effect of cin >> letter1 >> letter2 >> lastname;

60. 60 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Program Output Used to display results of program Also standard stream library iostream cout - name of stream associated with standard output device (monitor by default) Insertion operator (<<) for each element cout << data-element;

61. 61 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Program Output cout statement can be broken across lines Strings cannot be broken across lines Prompt messages used to inform program user to enter data Screen cursor is a moving marker indicating the position of where the next character will be displayed endl (or ‘\n’) causes a new line in output

62. 62 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Output Example cout << “The distance in kilometers is “ << kms << endl; If variable kms has value 16.09, the output is: The distance in kilometers is 16.09

63. 63 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley The return Statement Last line of main function is typically return 0; This transfers control from the program to the operating system, indicating that no error has occurred

64. 64 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Listing 2.3 General Form of a C++ Program

65. 65 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Program Style Use of spacing –one statement per line –blanks after comma, around operators –in between some lines of code for readability Use of comments –header section –document algorithm steps –describe difficult code

66. 66 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Program Style Naming conventions for identifiers –Variables in all lower case, with initial capital letter for additional words. No underscore. –Constants in all upper case, with underscores between words.

67. 67 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 2.6 Arithmetic Expressions int data type + - * / % Integer division examples - result is integer 15 / 3 = 5 15 / 2 = 7 0 / 15 = 0 15 / 0 undefined

68. 68 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Modulus for Integers Used only with integers Yields remainder - the result is integer Examples: 7 % 2 = 1 299 % 100 = 99 49 % 5 = 4 15 % 0 undefined 15 % -7 system dependent

69. 69 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Mixed-type Expressions E.g.: 4.6 / 2 evaluates to 2.3 Rule: when an integer and a floating point operand are combined by an operator, the integer gets converted to the floating point type Caveat: this rule is dependent on operator precedence rules

70. 70 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Mixed-type Assignments If the variable on left side of assignment is of different type than the type of the evaluated expression on the right side of =, the result of the expression must be converted to the appropriate type

71. 71 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Mixed-type Assignment Examples float a, b, x; int m, n; a=10;// result is 10.0 stored in a b = 3.5; m=5; n = 10; x = m / n;// result is 0 assigned to x m = b * 3;// result is 10 assigned to m

72. 72 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Order of Operator Precedence ( )nested expressions evaluated inside out unary +, - *, /, % binary +, - Highest Lowest Associativity Warning: watch out for the types of operands and the type of the result from evaluating each operand!

73. 73 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Figure 2.10 Evaluation for z - (a +b / 2) + w * -y

74. 74 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Figure 2.11 Evaluation tree for m = x + k / 2;

75. 75 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Mathematical Formulas in C++

76. 76 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Case Study: Coin Collection Problem statement Saving nickels and pennies and want to exchange these coins at the bank so need to know the value of coins in dollars and cents. Analysis –Need to count of nickels and pennies separately –Determine total value in cents –Use integer division by 100 to calculate dollars –Use modulus (%) to get remaining cents

77. 77 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Case Study: Data Requirements Problem input –string name –integer nickels –integer pennies Problem output –integer dollars –integer change Additional program variables –integer totalCents

78. 78 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Case Study: Formulas One dollar equals 100 pennies One nickel equals 5 pennies

79. 79 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Case Study: Design - Algorithm 1. Read in your niece’s first name 2. Read in the count of nickels and pennies 3. Compute the total value in cents 4. Find the value in dollars and loose change. 5. Display the value in dollars and loose change.

80. 80 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Case Study: Design - Algorithm 1. Read in your niece’s first name 2. Read in the count of nickels and pennies 3. Compute the total value in cents 3.1 totalCents is 5 times nickels plus pennies 4. Find the value in dollars and loose change. 4.1 dollars is integer quotient of totalCents and 100 4.2 change is integer remainer of totalCents and 100 5. Display the value in dollars and loose change.

81. 81 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Case Study: Implementation / used to implement step 4.1 % used to implement step 4.2 Verify that correct data types are used Verify mixed-type operations and promotions

82. 82 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Case Study: Testing Test results using various input combinations Verify results by hand or with calculator

83. 83 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Listing 2.4 Value of a coin collection // File: coins.cpp // Determines the value of a coin collection #include using namespace std; int main() { string name;// input: niece’s first name int pennies;// input: count of pennies int nickels; // input: count of nickels int dollars;// output: value of coins in dollars int change;// output: value of coins in cents int totalCents;// total cents represented

84. 84 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley // Read in your niece’s first name. cout << "Enter your first name: "; cin >> name; // Read in the count of nickels and pennies. cout << "Enter the number of nickels: "; cin >> nickels; cout << "Enter the number of pennies: "; cin >> pennies; Listing 2.4 Value of a coin collection (continued)

85. 85 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley // Compute the total value in cents. totalCents = 5 * nickels + pennies; // Find the value in dollars and change. dollars = totalCents / 100;// integer division change = totalCents % 100; // Display the value in dollars and change. cout << "Good work " << name << '!' << endl; cout << "Your collection is worth " << dollars << " dollars and " << change << " cents." << endl; return 0; } Listing 2.4 Value of a coin collection (continued)

86. 86 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley coins.cpp Sample Execution Enter your first name: Sally Enter the number of nickels: 30 Enter the number of pennies: 77 Good work Sally! Your collection is worth 2 dollars and 27 cents.

87. 87 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 2.7 Interactive Mode, Batch Mode, and Data Files Interactive mode - input from user via keyboard Batch mode - input via a file, no user interaction Input/output redirection can be used for batch mode

88. 88 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Input Redirection Requires a file already containing all input data before the program is executed At the time the program is executed, the input file is specified E.g. in UNIX metric < mydata Executes the program metric using the file mydata for input Echo printing often used with batch input

89. 89 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Output Redirection Sends ALL output to a file instead of to the display monitor Not typically used with interactive input mode, since even prompt messages will be sent to the output file E.g. in UNIX (not typical) metric > myoutput Both input AND output redirection metric myoutput

90. 90 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 2.8 Common Programming Errors Syntax –a grammatical error in the formation of a program statement –detected by the compiler –prevents translation of source code into object code, so no execution possible –messages are compiler dependent, so you must learn how your compiler identifiers errors

91. 91 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Common Programming Errors Run-time errors –detected and displayed during execution of a program –usually fatal - halts execution of code

92. 92 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Common Programming Errors Undetected errors –program runs to completion, but results are incorrect –often the result of input of the wrong type being entered

93. 93 Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Common Programming Errors Logic errors –caused by a faulty algorithm –often difficult to locate –can result in either a run-time or undetected error –system cannot identify - up to programmer to locate –vital to verify program output to ensure correct results

94. 94 Thank You For Your Attention!