1. Chapter 2:
Introduction to
C++

2. The Parts of a C++ Program
2.1
The Parts of a C++ Program

3. The Parts of a C++ Program
// sample C++ program
#include <iostream>
using namespace std;
int main() {
cout << "Hello, there!";
return 0; }
comment
preprocessor directive
which namespace to use
beginning of function named main
beginning of block for main
output statement
string literal
Send 0 to operating system
end of block for main

4. Special Characters Character Name Meaning // Double slash
Beginning of a comment #
Pound sign
Beginning of preprocessor directive
< >
Open/close brackets
Enclose filename in #include
( )
Open/close parentheses
Used when naming a function
{ }
Open/close brace
Encloses a group of statements
" "
Open/close quotation marks
Encloses string of characters ;
Semicolon
End of a programming statement

5. The #include Directive
2.3
The #include Directive

6. The #include Directive
Inserts the contents of another file into the program
This is a preprocessor directive, not part of C++ language
#include is preprocessed before compilation.
Do not place a semicolon at end of #include line

7. 2.2
The cout Object

8. The cout Object Displays output on the computer screen
You use the stream insertion operator << to send output to cout:
cout << "Programming is fun!";

9. The cout Object Can be used to send more than one item to cout:
cout << "Hello " << "there!";
Or:
cout << "Hello ";
cout << "there!";

10. The cout Object
This produces one line of output: cout << "Programming is "; cout << "fun!";

11. The endl Manipulator
You can use the endl manipulator to start a new line of output. This will produce two lines of output: cout << "Programming is" << endl; cout << "fun!";

12. The endl Manipulator
cout << "Programming is" << endl; cout << "fun!";
Programming is
fun!

13. The endl Manipulator You do NOT put quotation marks around endl
The last character in endl is a lowercase L, not the number 1.
endl
This is a lowercase L

14. Notice that the \n is INSIDE
The \n Escape Sequence
You can also use the \n escape sequence to start a new line of output. This will produce two lines of output: cout << "Programming is\n"; cout << "fun!";
Notice that the \n is INSIDE
the string.

15. The \n Escape Sequence
cout << "Programming is\n"; cout << "fun!";
Programming is
fun!

16. User input: “Hello !” > ./myProgram What is your name? Alice >
// include library of standard input and output commands #include <iostream> #include <string> using namespace std; int main() { // Begin main function string name; // create variable called name cout << "What is your name?"; cin >> name; // get name from user cout << "Hello "; // output "Hello " cout << name << "!\n"; // output "<name>!" return 0; // end program } // End main function
> ./myProgram
What is your name? Alice
>
> ./myProgram
What is your name? Alice
Hello Alice!
>
> ./myProgram
What is your name?
>

17. Variable declaration
// include library of standard input and output commands #include <iostream> using namespace std; #include <string> int main() { // Begin main function string name; // create variable called name cout << "What is your name?"; cin >> name; // get name from user cout << "Hello "; // output "Hello " cout << name << "!\n"; // output "<name>!" return 0; // end program } // End main function
“Declare” new variable by writing type followed by variable name.
More examples:
int age, weight; // multiple declarations

18. Input command
// include library of standard input and output commands #include <iostream> using namespace std; int main() { // Begin main function string name; // create variable called name cout << "What is your name?"; cin >> name; // get name from user cout << "Hello "; // output "Hello " cout << name << "!\n"; // output "<name>!" return 0; // end program } // End main function
cin >> varName; receives input from keyboard saves into the varName

19. Variables and Literals
2.4
Variables and Literals

20. Variables and Literals
Variable: a storage location in memory
Has a name and a type of data it can hold
Must be defined before it can be used:
int item;

21. Declaration, Initialization
Terminology:
Declare: creates space in memory. 'Labels the mailbox with the variable name'. Does NOT store anything. Just puts up the box. Example: int age;
Initialize: the initial time a value is put in that memory location. The first assignment. Example: age = 21;

22. Variable Definition in Program 2-7

23. Variables
A variable is a place (or location) in program memory that is used to hold a value.
All variables have a type that determines what can values it can hold.
The type tells how much space (memory) a variable has and how values are represented.
Remember, computers only have 0’s and 1’s to represent any value.

24. Variable Storage
1010
age
Variable Name, like your name on the box. Example: integer called age
Memory Address: like your street address, but just a number with no street)
Example:

25. Variable Storage 1010 21 age age
Variable Name, like your name on the box. Example: integer called age
Memory Address: like your street address, but just a number with no street)
Example:
Can store a value in there - of the proper type
Example: 21

26. Literals Literal: a value that is written into a program’s code.
"hello, there" (string literal)
12 (integer literal)

27. Integer Literal in Program 2-9
20 is an integer literal

28. String Literals in Program 2-9
These are string literals

29. 2.5
Identifiers

30. Identifiers
An identifier is a programmer-defined name for some part of a program: variables, functions, etc.

31. C++ Key Words
You cannot use any of the C++ key words as an identifier. These words have reserved meaning.

32. Variable Names
A variable name should represent the purpose of the variable. For example: itemsOrdered The purpose of this variable is to hold the number of items ordered.

33. Identifier Rules
The first character of an identifier must be an alphabetic character or and underscore ( _ ),
After the first character you may use alphabetic characters, numbers, or underscore characters.
Upper- and lowercase characters are distinct

34. Valid and Invalid Identifiers
REASON IF INVALID
totalSales
Yes
total_Sales
total.Sales No
Cannot contain .
4thQtrSales
Cannot begin with digit
totalSale$
Cannot contain $

35. Variables – locations in memory
Each variable has a location (address) in memory
Each location holds a value
Value can change as program progresses
Address Value
grade A P
Different variable types take up different amounts of memory
weight
140

36. 2.6
Integer Data Types

37. Integer Data Types
Integer variables can hold whole numbers such as 12, 7, and -99.

38. Defining Variables Variables of the same type can be defined
- On separate lines:
int length;
int width;
unsigned int area;
- On the same line:
int length, width;
Variables of different types must be in different declarations

39. Integer Types in Program 2-10
This program has three variables:
checking, miles, and diameter

40. Integer Literals
An integer literal is an integer value that is typed into a program’s code. For example: itemsOrdered = 15; In this code, 15 is an integer literal.

41. Integer Literals in Program 2-10

42. Integer Literals
Integer literals are stored in memory as ints by default
To store an integer constant in a long memory location, put ‘L’ at the end of the number: L
To store an integer constant in a long long memory location, put ‘LL’ at the end of the number: 324LL
Constants that begin with ‘0’ (zero) are base 8: 075
Constants that begin with ‘0x’ are base 16: 0x75A

43. 2.7
The char Data Type

44. The char Data Type
Used to hold characters or very small integer values
Usually 1 byte of memory
Numeric value of character from the character set is stored in memory:
CODE:
char letter;
letter = 'C';
MEMORY:
letter 67

45. Character Literals
Character literals must be enclosed in single quote marks. Example: 'A'

46. Character Literals in Program 2-14

47. Character Strings
A series of characters in consecutive memory locations:
"Hello"
Stored with the null terminator, \0, at the end:
Comprised of the characters between the " " H e l o \0

48. 2.8
The C++ string Class

49. The C++ string Class Special data type supports working with strings
#include <string>
Can define string variables in programs:
string firstName, lastName;
Can receive values with assignment operator:
firstName = "George";
lastName = "Washington";
Can be displayed via cout
cout << firstName << " " << lastName;

50. The string class in Program 2-15

51. Floating-Point Data Types
2.9
Floating-Point Data Types

52. Floating-Point Data Types
The floating-point data types are: float double long double
They can hold real numbers such as:
Stored in a form similar to scientific notation
All floating-point numbers are signed

53. Floating-Point Data Types

54. Floating-Point Literals
Can be represented in
Fixed point (decimal) notation:
E notation: (2en is 2x10 raised to the n power)
E e-5
Are double by default
Can be forced to be float ( f) or long double ( L)

55. These two are different
More complex output
float degrees;
degrees = 39.6;
cout << "The temperature today is ";
cout << degrees << " degrees" << endl;
These two are different
cout << "which is " << degrees – 32 ;
cout << " degrees above freezing " << endl;

56. Variable assignment Result: The temperature today is 39.6 degrees
which is 7.6 degrees above freezing

57. Example program
Let’s say we want to print the Earth’s distance from the Sun that is stored in a variable named distance
 billion meters
Let’s say we want to print the mass of the Sun that is stored in a variable named mass
1.989 × 10^30 kg

58. Floating-Point Data Types in Program 2-16

59. So far Programs can have…
preprocessing directives (e.g. #include), comments, a main function with {} enclosing statements.
The main function is required; it must have a return statement.
Input and output using cin and cout respectively.
cin >> variable; // reads input with “extraction” operator
cout << expression; // writes expression with “insertion” operator.
variables that are named memory locations
A variable name is an identifier. Identifiers can start with a _ or letter, but cannot be a keyword.
Variables have a type that tells the computer how to represent values: int, short, char, float, double, string and bool.

60. 2.10
The bool Data Type

61. The bool Data Type Represents values that are true or false
bool variables are stored as small integers
false is represented by 0, true by 1:
bool allDone = true;
bool finished = false;
allDone
finished 1

62. Boolean Variables in Program 2-17

63. Variable Assignments and Initialization
2.12
Variable Assignments and Initialization

64. Variable Assignments and Initialization
An assignment statement uses the = operator to store a value in a variable. item = 12;
This statement assigns the value 12 to the item variable.

65. Assignment
The variable receiving the value must appear on the left side of the = operator.
This will NOT work: // ERROR! 12 = item;

66. Variable Initialization
To initialize a variable means to assign it a value when it is defined:
int length = 12;
Can initialize some or all variables:
int length = 12, width = 5, area;

67. Variable Initialization in Program 2-19

68. Declaring Variables With the auto Key Word
C++ 11 introduces an alternative way to define variables, using the auto key word and an initialization value. Here is an example:
auto amount = 100;
The auto key word tells the compiler to determine the variable’s data type from the initialization value.
auto interestRate= 12.0;
auto stockCode = 'D';
auto customerNum = 459L;
int
double
char
long

69. 2.14
Arithmetic Operators

70. Arithmetic Operators Used for performing numeric calculations
C++ has unary, binary, and ternary operators:
unary (1 operand)
binary (2 operands)
ternary (3 operands) exp1 ? exp2 : exp3

71. Binary Arithmetic Operators
SYMBOL
OPERATION
EXAMPLE
VALUE OF ans +
addition
ans = 7 + 3; 10 -
subtraction
ans = 7 - 3; 4 *
multiplication
ans = 7 * 3; 21 /
division
ans = 7 / 3; 2 %
modulus
ans = 7 % 3; 1

72. A Closer Look at the / Operator
/ (division) operator performs integer division if both operands are integers
cout << 13 / 5; // displays 2
cout << 91 / 7; // displays 13
If either operand is floating point, the result is floating point
cout << 13 / 5.0; // displays 2.6
cout << 91.0 / 7; // displays 13.0

73. A Closer Look at the % Operator
% (modulus) operator computes the remainder resulting from integer division
cout << 13 % 5; // displays 3
% requires integers for both operands
cout << 13 % 5.0; // error

74. What does this program do?
Exercise: Build & Make it better!
#include <iostream> using namespace std; int main() { int dollars, coins; cout << "How many dollars do you have? "; cin >> dollars; coins = dollars*4; cout << "I will give you " << coins; cout << " coins.\n"; return 0; }

75. Let’s look at a bigger example
Our program helps us with Buying cookies.
We need to calculate the total cost of the cookies using this program.
What variables do we need?
How much does one cookie cost?
How may cookies did we buy?
Where can we put the total amount?

76. Variable declaration and initialization
All variables must be declared before they are used
double cookieCost; // cost of 1 cookie
int numCookiesPurchased;
double totalCost;
Variables are initialized with the first assignment statement
cookieCost = .50; // initialize variable
Declaration and initialization can also be performed in one line
float cookieCost = .50;

77. Buying Cookies
#include <iostream>// include io library using namespace std; int main() { // Begin main function int cookieCost = 1; // cost of 1 cookie int numCookiesPurchased; double totalCost; numCookiesPurchased = 3; totalCost = numCookiesPurchased * cookieCost; cout << "Cookies: "; cout << numCookiesPurchased << " at $"; cout << cookieCost << " each " << endl; cout << "Total cost = $" << totalCost << endl; return 0; // end program } // End main function

78. Buying Cookies
#include <iostream>// include io library using namespace std; int main() { // Begin main function int cookieCost = 1; // cost of 1 cookie int numCookiesPurchased; double subtotal; numCookiesPurchased = 3; subtotal = numCookiesPurchased * cookieCost; cout << "Cookies: "; cout << numCookiesPurchased << " at $"; cout << cookieCost << " each " << endl; cout << "Subtotal = $" << subtotal << endl; return 0; // end program } // End main function
But we don't always want to buy 3 cookies!

79. Buying Cookies with input
#include <iostream>// include io library using namespace std; int main() { // Begin main function int cookieCost = 1; // cost of 1 cookie int numCookiesPurchased; double subtotal; cout << "Number of Cookies? "; // prompt cin >> numCookiesPurchased; // read from keyboard subtotal = numCookiesPurchased * cookieCost; cout << "Cookies: "; cout << numCookiesPurchased << " at $"; cout << cookieCost << " each " << endl; cout << "Subtotal = $" << subtotal << endl; return 0; // end program } // End main function

80. Lab2: Cookies + Tax Using the above example:
Create a tax rate variable if tax is: .05 (not 5%)
What type should it be?
What is a good name?
Read in the tax rate
Calculate & print the tax
Print the total

81. Lab 2: Cookies Sample Output
Number of Cookies? 3 Cookies: 3 at $1 each Subtotal = $3 Tax Rate? .05 Tax = $0.15 Total = $3.15

82. Tax Basics Given: Subtotal of all the items taxRate
Tax = subtotal * taxRate;
Total is subtotal + subtotal * taxRate

83. Fancy Shorthand Operators
Extra stuff
Fancy Shorthand Operators

84. Shorthand Assignment Operators
int a = 6;
Standard assignment: a = 4;
Other assignments:
a += 3; // a = a + 3;
a -= 3; // a = a - 3;
a *= 3; // a = a * 3;
a /= 3; // a = a / 3;
a %= 3; // a = a % 3;

85. Increment and decrement
int c = 12;
Increment by 1: c++ evaluates to c=c + 1
Decrement by 1: c-- evaluates to c=c - 1

86. Determining the Size of a Data Type
2.11
Determining the Size of a Data Type

87. Determining the Size of a Data Type
The sizeof operator gives the size of any data type or variable:
double amount;
cout << "A double is stored in "
<< sizeof(double) << "bytes\n";
cout << "Variable amount is stored in "
<< sizeof(amount)
<< "bytes\n";

88. Assigning between types
int vs float
floats will be rounded to nearest integer and ints will be expanded to a precision float
int vs char
char will be converted to integer ASCII code and int will be converted to corresponding ASCII character
int vs bool
bool will be converted to 0 (if false) or 1 (if true) and int will be converted to false (of 0) or 1 (if not 0)

89. Type safety
Ideally, every variable will be used only according to its type
A variable will only be used after it has been initialized
Only operations defined for the variable’s declared type will be applied
Every operation defined for a variable leaves the variable with a valid value

90. 2.13
Scope

91. Scope
The scope of a variable: the part of the program in which the variable can be accessed
A variable cannot be used before it is declared.

92. Variable Out of Scope in Program 2-20

93. 2.15
Comments

94. Comments Used to document parts of the program
Intended for persons reading the source code of the program:
Indicate the purpose of the program
Describe the use of variables
Explain complex sections of code
Are ignored by the compiler

95. Single-Line Comments Begin with // through to the end of line:
int length = 12; // length in inches
int width = 15; // width in inches
int area; // calculated area
// calculate rectangle area
area = length * width;

96. Multi-Line Comments Begin with /*, end with */
Can span multiple lines:
/* this is a multi-line
comment */
Can begin and end on the same line:
int area; /* calculated area */

97. 2.16
Named Constants

98. Named Constants
Named constant (constant variable): variable whose content cannot be changed during program execution
Used for representing constant values with descriptive names:
const double TAX_RATE = ;
const int NUM_STATES = 50;
Often named in uppercase letters

99. Named Constants in Program 2-28

100. 2.17
Programming Style

101. Programming Style The visual organization of the source code
Includes the use of spaces, tabs, and blank lines
Does not affect the syntax of the program
Affects the readability of the source code

102. Variable names

103. Variable names, part 2 Choose meaningful names
Avoid acronyms (first letter of several words)
Avoid lengthy names
Good:
age, size, address, count, sumData
x, y, i – single letters as counting variables
Bad:
rbi, lda, xZ25, tla,sase neuron_response_magnitude

104. More about binary

105. The binary representation
int age = 65; assigns a binary code to memory:
char grade = 'A'; assigns a binary code to memory:
Every variable value is a number in binary, C++ interprets the binary number based on the variable type

106. Binary
Machine code (binary) is made only of 0s and 1s? Why? 1 Binary Digit is a Bit 8 Binary Digits is a Byte

107. Analogy from Base 10 Notation: N10 also called Decimal
Digits we use are:
0,1,2, Remember: Maximum digit = Base -1
Each Place value is 10 times the previous (start at the right)
Place value
10000
1000
100 10 1 2 4
310
Mult place value by digit +0
+ 1000
+200
+40 +3
Sum =

108. Base 2 Notation: N2 also called Binary
Binary Digits (bits) we use are:
0, 1 Maximum digit = Base -1
Each Place value is 2 times the previous (start at the right)
Place value 16 8 4 2 1 02
Mult place value by digit
+16
+ 0 +4 +2 +0
Sum
= 2210

109. #1. Convert this binary value to decimal
Place value 16 8 4 2 1 02

110. #2. Convert this binary value to decimal
Place value 16 8 4 2 1 02

111. #2. Convert this binary value to decimal
Place value 16 8 4 2 1 02
= 2610

112. #3. Convert this binary value to decimal1 02
= 2810

113. #3. Convert this binary value to decimal1 02

114. #4. Convert this binary value to decimal1 12
Note that, just like in the decimal system, if you put 0s in front of the number, it does not change its value.
So, is the same as

115. #4. Convert this binary value to decimal1 12
= 510

116. Convert Decimal (base 10) to Binary (base 2)16 8 4 2 1 22 ?
Sum: +
Similar to making change –
How do you hand someone 68 cents? Anyone?
Answer: Pick from high value coins to low
2 Quarters, (subtract 50, leaving 18 cents)
1 dime, leaving 8 cents
1 nickel, leaving 3 cents
then pick 3 pennies

117. Give the Binary Value for: 51016 8 4 2 1
Sum: + 1
Sum: +0 +4 +1

118. Give the Binary Value for: 121016 8 4 2 1
Sum: + 1
Sum: +0 +8 +4

119. Give the Binary Value for: 261016 8 4 2 1
Sum: + 1
Sum:
+16 +8 +0 +2

120. From ThinkGeek.com

121. From numbers to symbols: the ASCII table
American Standard Code for Information Interchange

122. Example Program Let’s think about a program to calculate hourly wages
Let’s consider that there may be overtime wages
Calculate both the regular wages and overtime wages
What do we need to know?
Remember gross pay?

123. Arithmetic Operators in Program 2-21