2. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Chapter 2 C++ Basics

3. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 3 Overview 2.1 Variables and Assignments 2.2 Input and Output 2.3 Data Types and Expressions 2.4 Simple Flow of Control 2.5 Program Style

4. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. 2.1 Variables and Assignments

5. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Variables are like small blackboards We can write a number on them We can change the number We can erase the number C++ variables are names for memory locations We can write a value in them We can change the value stored there We cannot erase the memory location Some value is always there Slide 2- 5 Display 2.1 Variables and Assignments

6. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Display 2.1 (2 /2) Slide 2- 6 Back Next

7. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 7 Identifiers Variables names are called identifiers Choosing variable names Use meaningful names that represent data to be stored First character must be a letter the underscore character Remaining characters must be letters numbers underscore character

8. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 8 Keywords Keywords (also called reserved words) Are used by the C++ language Must be used as they are defined in the programming language Cannot be used as identifiers

9. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Declaring Variables (Part 1) Before use, variables must be declared Tells the compiler the type of data to store Examples: int number_of_bars; double one_weight, total_weight; int is an abbreviation for integer. could store 3, 102, 3211, -456, etc. number_of_bars is of type integer double represents numbers with a fractional component could store 1.34, 4.0, -345.6, etc. one_weight and total_weight are both of type double

10. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 10 Declaring Variables (Part 2) Immediately prior to use int main() { … int sum; sum = score1 + score 2; … return 0; } At the beginning int main() { int sum; … sum = score1 + score2; … return 0; } Two locations for variable declarations

11. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 11 Declaring Variables (Part 3) Declaration syntax: Type_name Variable_1, Variable_2,... ; Declaration Examples: double average, m_score, total_score; double moon_distance; int age, num_students; int cars_waiting;

12. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 12 Assignment Statements An assignment statement changes the value of a variable total_weight = one_weight + number_of_bars; total_weight is set to the sum one_weight + number_of_bars Assignment statements end with a semi-colon The single variable to be changed is always on the left of the assignment operator ‘=‘ On the right of the assignment operator can be Constants -- age = 21; Variables -- my_cost = your_cost; Expressions -- circumference = diameter * 3.14159;

13. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 13 Assignment Statements and Algebra The ‘=‘ operator in C++ is not an equal sign The following statement cannot be true in algebra number_of_bars = number_of_bars + 3; In C++ it means the new value of number_of_bars is the previous value of number_of_bars plus 3

14. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 14 Initializing Variables Declaring a variable does not give it a value Giving a variable its first value is initializing the variable Variables are initialized in assignment statements double mpg; // declare the variable mpg = 26.3; // initialize the variable Declaration and initialization can be combined using two methods Method 1 double mpg = 26.3, area = 0.0, volume; Method 2 double mpg(26.3), area(0.0), volume;

15. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 15 Section 2.1 Conclusion Can you Declare and initialize two integers variables to zero? The variables are named feet and inches. Declare and initialize two variables, one int and one double? Both should be initialized to the appropriate form of 5. Give good variable names for identifiers to store the speed of an automobile? an hourly pay rate? the highest score on an exam?

16. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. 2.2 Input and Output

17. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 17 Input and Output A data stream is a sequence of data Typically in the form of characters or numbers An input stream is data for the program to use Typically originates at the keyboard at a file An output stream is the program’s output Destination is typically the monitor a file

18. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 18 Output using cout cout is an output stream sending data to the monitor The insertion operator "<<" inserts data into cout Example: cout << number_of_bars << " candy bars\n"; This line sends two items to the monitor The value of number_of_bars The quoted string of characters " candy bars\n" Notice the space before the ‘c’ in candy The ‘\n’ causes a new line to be started following the ‘s’ in bars A new insertion operator is used for each item of output

19. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 19 Examples Using cout This produces the same result as the previous sample cout << number_of_bars ; cout << " candy bars\n"; Here arithmetic is performed in the cout statement cout << "Total cost is $" << (price + tax); Quoted strings are enclosed in double quotes ("Walter") Don’t use two single quotes (') A blank space can also be inserted with cout << " " ; if there are no strings in which a space is desired as in " candy bars\n"

20. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 20 Include Directives Include Directives add library files to our programs To make the definitions of the cin and cout available to the program: #include Using Directives include a collection of defined names To make the names cin and cout available to our program: using namespace std;

21. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 21 Escape Sequences Escape sequences tell the compiler to treat characters in a special way '\' is the escape character To create a newline in output use \n – cout << "\n"; or the newer alternative cout << endl; Other escape sequences: \t -- a tab \\ -- a backslash character \" -- a quote character

22. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 22 Formatting Real Numbers Real numbers (type double) produce a variety of outputs double price = 78.5; cout << "The price is $" << price << endl; The output could be any of these: The price is $78.5 The price is $78.500000 The price is $7.850000e01 The most unlikely output is: The price is $78.50

23. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 23 Showing Decimal Places cout includes tools to specify the output of type double To specify fixed point notation setf(ios::fixed) To specify that the decimal point will always be shown setf(ios::showpoint) To specify that two decimal places will always be shown precision(2) Example:cout.setf(ios::fixed); cout.setf(ios::showpoint); cout.precision(2); cout << "The price is " << price << endl;

24. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 24 Input Using cin cin is an input stream bringing data from the keyboard The extraction operator (>>) removes data to be used Example: cout > number_of_bars; cin >> one_weight; This code prompts the user to enter data then reads two data items from cin The first value read is stored in number_of_bars The second value read is stored in one_weight Data is separated by spaces when entered

25. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 25 Reading Data From cin Multiple data items are separated by spaces Data is not read until the enter key is pressed Allows user to make corrections Example: cin >> v1 >> v2 >> v3; Requires three space separated values User might type 34 45 12

26. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 26 Designing Input and Output Prompt the user for input that is desired cout statements provide instructions cout > age; Notice the absence of a new line before using cin Echo the input by displaying what was read Gives the user a chance to verify data cout << age << " was entered." << endl;

27. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 27 Section 2.2 Conclusion Can you write an input statement to place a value in the variable the_number? Write the output statement to prompt for the value to store in the_number? Write an output statement that produces a newline? Format output of rational numbers to show 4 decimal places?

28. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. 2.3 Data Types and Expressions

29. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 29 Data Types and Expressions 2 and 2.0 are not the same number A whole number such as 2 is of type int A real number such as 2.0 is of type double Numbers of type int are stored as exact values Numbers of type double may be stored as approximate values due to limitations on number of significant digits that can be represented

30. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 30 Writing Integer constants Type int does not contain decimal points Examples: 34 45 1 89

31. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 31 Writing Double Constants Type double can be written in two ways Simple form must include a decimal point Examples: 34.1 23.0034 1.0 89.9 Floating Point Notation (Scientific Notation) Examples: 3.41e1 means 34.1 3.67e17 means 367000000000000000.0 5.89e-6means0.00000589 Number left of e does not require a decimal point Exponent cannot contain a decimal point

32. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Various number types have different memory requirements More precision requires more bytes of memory Very large numbers require more bytes of memory Very small numbers require more bytes of memory Slide 2- 32 Display 2.2 Other Number Types

33. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Display 2.2 Slide 2- 33 Back Next

34. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 34 Integer types long or long int (often 4 bytes) Equivalent forms to declare very large integers long big_total; long int big_total; short or short int (often 2 bytes) Equivalent forms to declare smaller integers short small_total; short int small_total;

35. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 35 Floating point types long double (often 10 bytes) Declares floating point numbers with up to 19 significant digits long double big_number; float (often 4 bytes) Declares floating point numbers with up to 7 significant digits float not_so_big_number;

36. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 36 Type char Computers process character data too char Short for character Can be any single character from the keyboard To declare a variable of type char: char letter;

37. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 37 char constants Character constants are enclosed in single quotes char letter = 'a'; Strings of characters, even if only one character is enclosed in double quotes "a" is a string of characters containing one character 'a' is a value of type character

38. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. cin skips blanks and line breaks looking for data The following reads two characters but skips any space that might be between char symbol1, symbol2; cin >> symbol1 >> symbol2; User normally separate data items by spaces J D Results are the same if the data is not separated by spaces JD Slide 2- 38 Display 2.3 Reading Character Data

39. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Display 2.3 Slide 2- 39 Back Next

40. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 40 Type string string is a class, different from the primitive data types discussed so far Difference is discussed in Chapter 8 Use double quotes around the text to store into the string variable Requires the following be added to the top of your program: #include To declare a variable of type string: string name = "Apu Nahasapeemapetilon"; Display 2.4

41. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Display 2.4 Slide 2- 41 Back Next

42. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 42 Type Compatibilities In general store values in variables of the same type This is a type mismatch: int int_variable; int_variable = 2.99; If your compiler allows this, int_variable will most likely contain the value 2, not 2.99

43. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 43 int  double (part 1) Variables of type double should not be assigned to variables of type int int int_variable; double double_variable; double_variable = 2.00; int_variable = double_variable; If allowed, int_variable contains 2, not 2.00

44. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 44 int  double (part 2) Integer values can normally be stored in variables of type double double double_variable; double_variable = 2; double_variable will contain 2.0

45. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 45 char   int The following actions are possible but generally not recommended! It is possible to store char values in integer variables int value = 'A'; value will contain an integer representing 'A' It is possible to store int values in char variables char letter = 65;

46. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 46 bool   int The following actions are possible but generally not recommended! Values of type bool can be assigned to int variables True is stored as 1 False is stored as 0 Values of type int can be assigned to bool variables Any non-zero integer is stored as true Zero is stored as false

47. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 47 Arithmetic Arithmetic is performed with operators + for addition - for subtraction * for multiplication / for division Example: storing a product in the variable total_weight total_weight = one_weight * number_of_bars;

48. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 48 Results of Operators Arithmetic operators can be used with any numeric type An operand is a number or variable used by the operator Result of an operator depends on the types of operands If both operands are int, the result is int If one or both operands are double, the result is double

49. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 49 Division of Doubles Division with at least one operator of type double produces the expected results. double divisor, dividend, quotient; divisor = 3; dividend = 5; quotient = dividend / divisor; quotient = 1.6666… Result is the same if either dividend or divisor is of type int

50. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 50 Division of Integers Be careful with the division operator! int / int produces an integer result (true for variables or numeric constants) int dividend, divisor, quotient; dividend = 5; divisor = 3; quotient = dividend / divisor; The value of quotient is 1, not 1.666… Integer division does not round the result, the fractional part is discarded!

51. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. % operator gives the remainder from integer division int dividend, divisor, remainder; dividend = 5; divisor = 3; remainder = dividend % divisor; The value of remainder is 2 Slide 2- 51 Display 2.5 Integer Remainders

52. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Display 2.5 Slide 2- 52 Back Next

53. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Use spacing to make expressions readable Which is easier to read? x+y*z or x + y * z Precedence rules for operators are the same as used in your algebra classes Use parentheses to alter the order of operations x + y * z ( y is multiplied by z first) (x + y) * z ( x and y are added first) Slide 2- 53 Display 2.6 Arithmetic Expressions

54. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Display 2.6 Slide 2- 54 Back Next

55. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 55 Operator Shorthand Some expressions occur so often that C++ contains to shorthand operators for them All arithmetic operators can be used this way += count = count + 2; becomes count += 2; *= bonus = bonus * 2; becomes bonus *= 2; /= time = time / rush_factor; becomes time /= rush_factor; %= remainder = remainder % (cnt1+ cnt2); becomes remainder %= (cnt1 + cnt2);

56. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. 2.4 Simple Flow of Control

57. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 57 Simple Flow of Control Flow of control The order in which statements are executed Branch Lets program choose between two alternatives

58. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 58 Branch Example To calculate hourly wages there are two choices Regular time ( up to 40 hours) gross_pay = rate * hours; Overtime ( over 40 hours) gross_pay = rate * 40 + 1.5 * rate * (hours - 40); The program must choose which of these expressions to use

59. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 59 Designing the Branch Decide if (hours >40) is true If it is true, then use gross_pay = rate * 40 + 1.5 * rate * (hours - 40); If it is not true, then use gross_pay = rate * hours;

60. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. if-else statement is used in C++ to perform a branch if (hours > 40) gross_pay = rate * 40 + 1.5 * rate * (hours - 40); else gross_pay = rate * hours; Slide 2- 60 Display 2.7 Display 2.8 Implementing the Branch

61. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Display 2.7 Slide 2- 61 Back Next

62. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Display 2.8 Slide 2- 62 Back Next

63. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Boolean expressions are expressions that are either true or false comparison operators such as '>' (greater than) are used to compare variables and/or numbers (hours > 40) Including the parentheses, is the boolean expression from the wages example A few of the comparison operators that use two symbols (No spaces allowed between the symbols!) >= greater than or equal to != not equal or inequality = = equal or equivalent Slide 2- 63 Display 2.9 Boolean Expressions

64. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Display 2.9 Slide 2- 64 Next Back

65. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 65 if-else Flow Control (1) if (boolean expression) true statement else false statement When the boolean expression is true Only the true statement is executed When the boolean expression is false Only the false statement is executed

66. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 66 if-else Flow Control (2) if (boolean expression) { true statements } else { false statements } When the boolean expression is true Only the true statements enclosed in { } are executed When the boolean expression is false Only the false statements enclosed in { } are executed

67. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 67 AND Boolean expressions can be combined into more complex expressions with && -- The AND operator True if both expressions are true Syntax: (Comparison_1) && (Comparison_2) Example: if ( (2 < x) && (x < 7) ) True only if x is between 2 and 7 Inside parentheses are optional but enhance meaning

68. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 68 OR | | -- The OR operator (no space!) True if either or both expressions are true Syntax: (Comparison_1) | | (Comparison_2) Example: if ( ( x = = 1) | | ( x = = y) ) True if x contains 1 True if x contains the same value as y True if both comparisons are true

69. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 69 NOT ! -- negates any boolean expression !( x < y) True if x is NOT less than y !(x = = y) True if x is NOT equal to y ! Operator can make expressions difficult to understand…use only when appropriate

70. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 70 Inequalities Be careful translating inequalities to C++ if x < y < z translates as if ( ( x < y ) && ( y < z ) ) NOT if ( x < y < z )

71. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 71 Pitfall: Using = or == ' = ' is the assignment operator Used to assign values to variables Example: x = 3; '= = ' is the equality operator Used to compare values Example: if ( x == 3) The compiler will accept this error: if (x = 3) but stores 3 in x instead of comparing x and 3 Since the result is 3 (non-zero), the expression is true

72. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. A compound statement is more than one statement enclosed in { } Branches of if-else statements often need to execute more that one statement Example: if (boolean expression) { true statements } else { false statements } Slide 2- 72 Display 2.10 Compound Statements

73. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 73 Branches Conclusion Can you Write an if-else statement that outputs the word High if the value of the variable score is greater than 100 and Low if the value of score is at most 100? The variables are of type int. Write an if-else statement that outputs the word Warning provided that either the value of the variable temperature is greater than or equal to 100, or the of the variable pressure is greater than or equal to 200, or both. Otherwise, the if_else sttement outputs the word OK. The variables are of type int.

74. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. When an action must be repeated, a loop is used C++ includes several ways to create loops We start with the while-loop Example: while (count_down > 0) { cout << "Hello "; count_down -= 1; } Output: Hello Hello Hello when count_down starts at 3 Slide 2- 74 Display 2.11 Simple Loops

75. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 75 While Loop Operation First, the boolean expression is evaluated If false, the program skips to the line following the while loop If true, the body of the loop is executed During execution, some item from the boolean expression is changed After executing the loop body, the boolean expression is checked again repeating the process until the expression becomes false A while loop might not execute at all if the boolean expression is false on the first check

76. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. while (boolean expression is true) { statements to repeat } Semi-colons are used only to end the statements within the loop While (boolean expression is true) statement to repeat Slide 2- 76 Display 2.12 while Loop Syntax

77. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. A variation of the while loop. A do-while loop is always executed at least once The body of the loop is first executed The boolean expression is checked after the body has been executed Syntax: do { statements to repeat } while (boolean_expression); Slide 2- 77 Display 2.13 Display 2.14 do-while loop

78. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 78 Increment/Decrement Unary operators require only one operand + in front of a number such as +5 - in front of a number such as -5 ++ increment operator Adds 1 to the value of a variable x ++; is equivalent to x = x + 1; -- decrement operator Subtracts 1 from the value of a variable x --; is equivalent to x = x – 1;

79. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Bank charge card balance of $50 2% per month interest How many months without payments before your balance exceeds $100 After 1 month: $50 + 2% of $50 = $51 After 2 months: $51 + 2% of $51 = $52.02 After 3 months: $52.02 + 2% of $52.02 … Slide 2- 79 Display 2.15 Sample Program

80. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 80 Infinite Loops Loops that never stop are infinite loops The loop body should contain a line that will eventually cause the boolean expression to become false Example: Print the odd numbers less than 12 x = 1; while (x != 12) { cout << x << endl; x = x + 2; } Better to use this comparison: while ( x < 12)

81. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 81 Section 2.4 Conclusion Can you Show the output of this code if x is of type int? x = 10; while ( x > 0) { cout << x << endl; x = x – 3; } Show the output of the previous code using the comparison x 0?

82. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. 2.5 Program Style

83. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 83 Program Style A program written with attention to style is easier to read easier to correct easier to change

84. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 84 Program Style - Indenting Items considered a group should look like a group Skip lines between logical groups of statements Indent statements within statements if (x = = 0) statement; Braces {} create groups Indent within braces to make the group clear Braces placed on separate lines are easier to locate

85. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 85 Program Style - Comments // is the symbol for a single line comment Comments are explanatory notes for the programmer All text on the line following // is ignored by the compiler Example: //calculate regular wages gross_pay = rate * hours; /* and */ enclose multiple line comments Example: /* This is a comment that spans multiple lines without a comment symbol on the middle line */

86. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 86 Program Style - Constants Number constants have no mnemonic value Number constants used throughout a program are difficult to find and change when needed Constants Allow us to name number constants so they have meaning Allow us to change all occurrences simply by changing the value of the constant

87. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. const is the keyword to declare a constant Example: const int WINDOW_COUNT = 10; declares a constant named WINDOW_COUNT Its value cannot be changed by the program like a variable It is common to name constants with all capitals Slide 2- 87 Display 2.16 Constants

88. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Slide 2- 88 Section 2.5 Conclusion Can you Create a named constant of type double? Determine if a program can modify the value of a constant? Describe the benefits of comments? Explain why indenting is important in a program? Explain why blank lines are important in a program?

89. C++ Tutorials Dr. AHMED ABDELTAWAB TELBA King Saud University Collage of Engineering Electrical Engineering Department Office +966 1 4678800 atelba@ksu.edu.sa http://faculty.ksu.edu.sa/atelba/default.aspx atelba@ksu.edu.sa http://faculty.ksu.edu.sa/atelba/default.aspx

90. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. int y; // declare y as an integer variable y = 4; // 4 evaluates to 4, which is then assigned to y y = 2 + 5; // 2 + 5 evaluates to 7, which is then assigned to y int x; // declare x as an integer variable x = y; // y evaluates to 7, which is then assigned to x. x = x; // x evaluates to 7, which is then assigned to x (useless!) x = x + 1; // x + 1 evaluates to 8, which is then assigned to x. #include int main() { using namespace std; // gives us access to cout and endl int x; // declare an integer variable named x // print the value of x to the screen (dangerous, because x is uninitialized) cout << x << endl; }

91. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. #include using namespace std; int main() { cout << "Enter a number: "; // ask user for a number int x; cin >> x; // read number from console and store it in x cout << "You entered " << x << endl; return 0; } Cin>> & cout<<

92. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. int x = 5; x = x - 2; cout << x << endl; // #1 int y = x; cout << y << endl; // #2 // x + y is an r-value in this context, so evaluate their values cout << x + y << endl; // #3 cout << x << endl; // #4 int z; cout << z << endl; // #5

93. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Let us look at a simple code that would print the words Hello World. #include using namespace std; // main() is where program execution begins. int main() { cout << "Hello World"; // prints Hello World return 0; } C++ Program Structure:

94. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. x = y; y = y+1; add(x, y); same as: x = y; y = y+1; add(x, y);

95. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. /* This is a comment */ /* C++ comments can also * span multiple lines */A comment can also start with //, extending to the end of the line. For example: #include using namespace std; main() { cout << "Hello World"; // prints Hello World return 0; } This is a comment

96. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. /* Comment out printing of Hello World: cout << "Hello World"; // prints Hello World */

97. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. int x; x = 5; cout << x; #include using namespace std; int main() { cout << "Hello world!" << endl; return 0; } Structure of a program

98. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. /* Simple hello world program*/ # include // This is include directive using namespace std; int main() { cout << “Hello World!”; //C++ statement return 0; } Hello World!

99. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. #include using namespace std; main() { int z,x; for(z=1;z<=5;z++){ cout<<"******\n" ; for(x=0;x<=z-1;x++) cout<<" " ; system("pause"); }} A Simple Program

100. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. #include using namespace std; main() { int z,x; for(z=1;z<=5;z++){ for(x=z;x<=5;x++) cout<<" " ; cout<<"*\n" ; } system("pause");} Simple program

101. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. TypeKeyword Booleanbool Characterchar Integerint Floating pointfloat Double floating pointdouble Valuelessvoid Wide characterwchar_t Primitive Built-in Types: C++ offer the programmer a rich assortment of built-in as well as user defined data types. Following table list down seven basic C++ data types:

102. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. TypeTypical Bit WidthTypical Range char1byte-127 to 127 or 0 to 255 unsigned char1byte0 to 255 signed char1byte-127 to 127 int4bytes-2147483648 to 2147483647 unsigned int4bytes0 to 4294967295 signed int4bytes-2147483648 to 2147483647 short int2bytes-32768 to 32767 unsigned short intRange0 to 65,535 signed short intRange-32768 to 32767 long int4bytes-2,147,483,647 to 2,147,483,647 signed long int4bytessame as long int unsigned long int4bytes0 to 4,294,967,295 float4bytes+/- 3.4e +/- 38 (~7 digits) double8bytes+/- 1.7e +/- 308 (~15 digits) long double8bytes+/- 1.7e +/- 308 (~15 digits) wchar_t2 or 4 bytes1 wide character

103. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. #include using namespace std; int main() { cout << "Size of char : " << sizeof(char) << endl; cout << "Size of int : " << sizeof(int) << endl; cout << "Size of short int : " << sizeof(short int) << endl; cout << "Size of long int : " << sizeof(long int) << endl; cout << "Size of float : " << sizeof(float) << endl; cout << "Size of double : " << sizeof(double) << endl; cout << "Size of wchar_t : " << sizeof(wchar_t) << endl; return 0; }

104. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Enumerated Types: An enumerated type declares an optional type name and a set of zero or more identifiers that can be used as values of the type. Each enumerator is a constant whose type is the enumeration. To create an enumeration requires the use of the keyword enum. The general form of an enumeration type is: enum enum-name { list of names } var-list; enum color { red, green, blue } c; c = blue; enum color { red, green=5, blue }; enum enum-name { list of names } var-list; Here, The enum-name is the enumeration's type name. The list of names is comma separated. For example, the following code defines an enumeration of colors called colors and the variable c of type color. Finally, c is assigned the value "blue". enum color { red, green, blue } c; c = blue;By default, the value of the first name is 0, the second name has the value 1, the third has the value 2, and so on. But you can give a name a specific value by adding an initializer. For example, in the following enumeration, green will have the value 5. enum color { red, green=5, blue };Here blue will have a value of 6 because each name will be one greater than the one that precedes it. Enumerated Types:

105. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Some examples are: int d = 3, f = 5; // initializing d and f. byte z = 22; // initializes z. double pi = 3.14159; // declares an approximation of pi. char x = 'x'; // the variable x has the value 'x'. Variable Initialization in C++:

106. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Example #include using namespace std; int main () { // Variable declaration: int a, b; int c; float f; // actual initialization a = 10; b = 20; c = a + b; cout << c << endl ; f = 70.0/3.0; cout << f << endl ; system(“pause”); return 0; }

107. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Local Variables: Variables that are declared inside a function or block are local variables. They can be used only by statements that are inside that function or block of code. Local variables are not known to functions outside their own. Following is the example using local variables:

108. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Local variable declaration #include using namespace std; int main () { // Local variable declaration: int a, b; int c; // actual initialization a = 10; b = 20; c = a + b; cout << c; return 0; }

109. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Global Variables: Global variables are defined outside of all the functions, usually on top of the program. The global variables will hold their value throughout the lifetime of your program. A global variable can be accessed by any function. That is, a global variable is available for use throughout your entire program after its declaration. Following is the example using global and local variables:

110. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Global variable declaration: #include using namespace std; // Global variable declaration: int g; int main () { // Local variable declaration: int a, b; // actual initialization a = 10; b = 20; g = a + b; cout << g; return 0; }

111. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. #include using namespace std; // Global variable declaration: int g = 20; int main () { // Local variable declaration: int g = 10; cout << g; return 0; }

112. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Escape sequenceMeaning \\\ character \'' character \"" character \?? character \aAlert or bell \bBackspace \fForm feed \nNewline \rCarriage return \tHorizontal tab \vVertical tab \oooOctal number of one to three digits \xhh...Hexadecimal number of one or more digits

113. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Simple program #include using namespace std; int main() { cout << "Hello\tWorld\n\n"; return 0; }

114. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. The #define Preprocessor: Following is the form to use #define preprocessor to define a constant: #define identifier value Following example explains it in detail: #include using namespace std; #define LENGTH 10 #define WIDTH 5 #define NEWLINE '\n' int main() { int area; area = LENGTH * WIDTH; cout << area; cout << NEWLINE; return 0; }

115. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. #include using namespace std; int main() { const int LENGTH = 10; const int WIDTH = 5; const char NEWLINE = '\n'; int area; area = LENGTH * WIDTH; cout << area; cout << NEWLINE; return 0; }

116. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. difference between signed and unsigned integers #include using namespace std; /* This program shows the difference between * signed and unsigned integers. */ int main() { short int i; // a signed short integer short unsigned int j; // an unsigned short integer j = 50000; i = j; cout << i << " " << j; system("pause"); return 0;}

117. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. #include using namespace std; main() { int a = 21; int b = 10; int c ; c = a + b; cout << "Line 1 - Value of c is :" << c << endl ; c = a - b; cout << "Line 2 - Value of c is :" << c << endl ; c = a * b; cout << "Line 3 - Value of c is :" << c << endl ; c = a / b; cout << "Line 4 - Value of c is :" << c << endl ; c = a % b; cout << "Line 5 - Value of c is :" << c << endl ; c = a++; cout << "Line 6 - Value of c is :" << c << endl ; c = a--; cout << "Line 7 - Value of c is :" << c << endl ; System(“pause”); return 0; }

118. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. OperatorDescriptionExample +Adds two operandsA + B will give 30 -Subtracts second operand from the first A - B will give -10 *Multiply both operandsA * B will give 200 /Divide numerator by de- numerator B / A will give 2 %Modulus Operator and remainder of after an integer division B % A will give 0 ++Increment operatorIncrement operator, increases integer value by one A++ will give 11 --Decrement operatorDecrement operator, decreases integer value by one A-- will give 9

119. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Relational Operators: There are following relational operators supported by C++ language Assume variable A holds 10 and variable B holds 20 then: OperatorDescriptionExample ==Checks if the value of two operands is equal or not, if yes then condition becomes true. (A == B) is not true. !=Checks if the value of two operands is equal or not, if values are not equal then condition becomes true. (A != B) is true. >Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true. (A > B) is not true. <Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true. (A < B) is true. >=Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true. (A >= B) is not true. <=Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true. (A <= B) is true.

120. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. #include using namespace std; main () { int i,j,k,p,m,n; float a,b,c,d,e,f,g,h,x,y; i=5; j=5; k=11; p=3; x=3.0; y=4.0; printf("...... Initial values......\n"); printf("i=%4d, j=%4d\nk=%4d, p=%4d\nx=%4.2f, y=%4.2f\n\n", i,j,k,p,x,y); cout << “i- Value of c is :" << c << endl ; /*--------------- Section 1 -------------------*/ a=x+y; b=x-y; c=x*y; d=x/y; e=d+3.0; f=d+3; i=i+1; j=j+1; printf("...... Section 1 output......\n"); printf("a=%5.2f, b=%5.2f\nc=%5.2f, d=%5.2f\n" "e=%5.2f, f=%5.2f\ni=%5d, j=%5d \n\n", a,b, c,d, e,f, i,j); /*--------------- Section 2 -------------------*/ m=k%p; n=p%k; i++; ++j; e--; --f; printf("...... Section 2 output......\n"); printf("m=%4d, n=%4d\ni=%4d, j=%4d\n" "e=%4.2f, f=%4.2f\n",m,n, i,j, e,f); }

121. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Logical Operators: There are following logical operators supported by C++ language Assume variable A holds 1 and variable B holds 0 then:

122. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Logical operations in C++ #include using namespace std; main() { int a = 5; int b = 20; int c ; if ( a && b ) { cout << "Line 1 - Condition is true"<< endl ; } if ( a || b ) { cout << "Line 2 - Condition is true"<< endl ; } /* Let's change the values of a and b */ a = 0; b = 10; if ( a && b ) { cout << "Line 3 - Condition is true"<< endl ; } else { cout << "Line 4 - Condition is not true"<< endl ; } if ( !(a && b) ) { cout << "Line 5 - Condition is true"<< endl ; } return 0; } Line 1 - Condition is true Line 2 - Condition is true Line 4 - Condition is not true Line 5 - Condition is true

123. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Logical gates pqp &q (and) p | q (or) p ^ q xor 00000 01011 11110 10011

124. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. #include main() { cout<<"hi\nhussien\nahammed\ntaleb"; } /// cin>>var1>>var2; // cin>> x; C++ //scanf("%f",& x); c

125. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. #include using namespace std; main() { int a = 21; int b = 10; int c ; if( a == b ) { cout << "Line 1 - a is equal to b" << endl ; } else { cout << "Line 1 - a is not equal to b" << endl ; } if ( a < b ) { cout << "Line 2 - a is less than b" << endl ; } else { cout << "Line 2 - a is not less than b" << endl ; } if ( a > b ) { cout << "Line 3 - a is greater than b" << endl ; } else { cout << "Line 3 - a is not greater than b" << endl ; } /* Let's change the values of a and b */ a = 5; b = 20; if ( a <= b ) { cout << "Line 4 - a is either less than \ or euqal to b" << endl ; } if ( b >= a ) { cout << "Line 5 - b is either greater than \ or equal to b" << endl ; } return 0; }

126. Copyright © 2008 Pearson Addison-Wesley. All rights reserved.

127. #include main() { int first, seconds, sum; cin>> first; cout<<"+\n"; cin>> seconds; sum= first+ seconds; cout<<"---------\nsum="<< sum ; }

128. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. Reslt=a – c / d a=5,c=10,d=2 Reslt=5 – 10 / 2

129. Copyright © 2008 Pearson Addison-Wesley. All rights reserved. #include main() { int a=2; int item; item=3+a++; cout<<"FirstTry="<< item ; item=3+ a; cout<<"\nSecondTry="<< item ; }

130. Copyright © 2008 Pearson Addison-Wesley. All rights reserved.

131. Slide 2- 131 Chapter 2 -- End

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