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Chapter 2
Introduction to C++
Starting Out with C++ Early Objects
Seventh Edition
by Tony Gaddis, Judy Walters,
and Godfrey Muganda
2-1

2.1 Parts of a C++ Program
// sample C++ program
#include <iostream>
using namespace std;
int main()
{
cout << "Hello, there!";
return 0;
}
2-2
comment
preprocessor directive
which namespace to use
beginning of function named main
beginning of block for main
output statement
send 0 back to operating system
end of block for main

Special Characters (pg. 30)
2-3
Character Name Description
// Double Slash Begins a comment
# Pound Sign Begins preprocessor directive
< > Open, Close Brackets Encloses filename used in
#include directive
( ) Open, Close Parentheses Used with function & other
times
{ } Open, Close Braces Encloses a group of statements
" " Open, Close Quote Marks Encloses string of characters
; Semicolon Ends a programming statement

Important Details
• C++ is case-sensitive. Uppercase &
lowercase characters are different
characters. ‘Main’ is not the same as
‘main’.
• Every { must have a corresponding },
and vice-versa.
Watch for the “NOTE” and “WARNING” boxes n
your text. They provide good information! 2-4

2.2 The cout Object
• Displays information on computer screen
– Equivalent to “print to screen”
• Use << to send information to cout
cout << "Hello, there!";
• Can use << to send multiple items to cout
cout << "Hello, " << "there!";
Or equivalently
cout << "Hello, ";
cout << "there!"; 2-5

cout
• << stream insertion operator
• Must be between each different element
cout << “Total is ” << Tot;
Total is 49
2-6

Starting a New Line
• To get multiple lines of output on screen
- Use endl
cout << "Hello, there!" << endl;
- Use n in an output string
cout << "Hello, there!n";
2-7

New lines of output
endl – a command
• Causes a new line of output
• Dumps the output buffer to output file
‘n’ – a special character
• Causes a new line of output only
• MUST be inside quotes
• Side-effect: when used with file output,
some output may not get printed
Test question
2-8

Common Escape Sequences (p.35)
~~ MUST be contained in quotes
~~ Considered a single character
n Newline
t Tab
a Alarm
b Backspace
r Return (same line)
Prints 1
’ Prints single quote
” Prints double quote 2-9

Examples
cout << “’Hellon Mary’”;
‘Hello
Mary’
Note: the single space in front of Mary
2-10

2.3 The #include Directive
• Inserts the contents of another file into the
program
• Is a preprocessor directive
– Not part of the C++ language
– Not seen by compiler
• Example:
#include <iostream>
There will be several different files that we will include
for different purposes. 2-11
No
semicolon;
goes here

2.4 Standard & Pre-standard C++
Older-style C++ programs
• Use .h at end of header files
#include <iostream.h>
• Do not use using namespace convention
• May not compile with a standard C++ compiler
We WILL NOT use the .h format.
2-12

2.5 Variables, Constants, & the
Assignment Statement
• Variable
– Has a name (identifier) & a type of data it can hold
char letter;
– Is used to reference a location in memory where a
value can be stored
– Must be defined before it can be used
– The value that is stored can be changed,
i.e., it can “vary”
– When use name in program, referring to data stored
in the corresponding memory location.
2-13
variable
name
data type

Variables
– Represents a location in memory
– Stores/Holds on data value
– If a new value is stored in the variable, it
replaces previous value
– The previous value is overwritten and can no
longer be retrieved
int age;
age = 17; // age is 17
cout << age; // Displays 17
age = 18; // Now age is 18
cout << age; // Displays 18 2-14

Assignment Statement
• Uses the = operator (“is assigned”)
• Has single variable on left side and a
value or expression on right side
• Copies the value on right into the
variable on left, i.e. it’s memory location
item = 12;
total = 15 + 2;
tax = Bal * 0.0825; 2-15

Constant
• Data item whose value does not change
during program execution – NEVER
• Is also called a literal
'A' // character constant
"Hello" // string literal
12 // integer constant
3.14 // floating-point constant
Often a test question
2-16

2.6 Identifiers
• Programmer-chosen names to represent parts of
program, such as variables & constants
– Any length, but you must type it repeatedly
• Name indicates use of the identifier
• Cannot use C++ key words as identifiers
– See Table 2.4 – pg. 41
• Legal form (this is a question on test 1)
– Must begin with alphabetic character or _
– followed by alphabetic, numeric, or _ . Alpha may be
upper- or lowercase
2-17

Valid and Invalid
Identifiers
2-18
IDENTIFIER VALID? REASON IF INVALID
totalSales Yes
total_Sales Yes
total.Sales No Cannot contain period
4thQtrSales No Cannot begin with digit
totalSale$ No Cannot contain $

2.7 Integer Data Types
• Designed to hold whole numbers
• Can be signed or unsigned
12 -6 +3
• Available in different sizes (i.e., number of
bytes): short, int, and long
• size of short  size of int  size of long
Table 2-6 – pg. 44
2-19

Defining Variables
• Variables of the same type can be defined
- In separate statements
int length;
int width;
- In the same statement
int length, width;
• Variables of different types must be defined
in separate statements
int length;
short width;
2-20

2.8 The char Data Type
• Used to hold single characters
– Or very small integer values: 0 to 15 *but don’t*
• (Usually) Occupies 1 byte of memory
• A numeric code representing the character
is stored in memory
2-21
SOURCE CODE MEMORY
char letter = ‘c'; letter
0110 0011

String Constant
• Can be stored a series of characters in
consecutive memory locations
"Hello"
• Stored with null terminator, 0, at end
• Is comprised of characters between
the " "
2-22
H e l l o 0

A character or a string constant?
• A character constant is a single character,
enclosed in single quotes:
'C'
• A string constant is a sequence of
characters enclosed in double quotes:
"Hello, there!"
• A single character in double quotes is a
string constant, not a character constant:
"C"
2-23

2.9 The C++ string Class
• Must #include <string> to create & use
string objects
• Can define string variables in programs
string name;
• Can assign values to string variables with
assignment operator
name = "George";
• Can display with cout
cout << name;
• Note: # include <string> unnecessary if using
only string literals
cout << “George”; 2-24

2.10 Floating-Point Data Types
• Hold real numbers
12.45 -3.8
• Stored in form similar to scientific notation
• Numbers are all signed
• Types are
– float - 4 bytes
– double – 8 bytes
– long double – 8 bytes (usually)
2-25

Floating Point Examples
float Item, Tax;
Item = 5.34;
Tax = Item * 0.0825;
cout << Item << “ “ << Tax;
----------------------
5.34 0.44055
Note: w/o spaces in quotes
5.340.44055 2-26

Floating-point Constants
• Can be represented in
- Fixed point (decimal) notation:
31.4159 0.0000625
- E-notation: (we won’t use but need to recognize)
3.14159E1 6.25e-5
•Usually indicate extremely large
or small value
• Are double by default
2-27

Assigning Floating-point
Values to Integer Variables
If floating-point value is assigned to an
integer variable
– The fractional part will be truncated
(i.e., “chopped off” & discarded)
– The value is NOT rounded
int rainfall = 3.88;
cout << rainfall; // Displays 3
2-28

2.11 The bool Data Type
• Represents values that are true or false
• bool values are stored as short integers
• false is represented by 0, true by 1
bool allDone = true;
bool finished = false;
Note: Any non-zero value is considered
true. 2-29
allDone finished
1 0

2.12 Determining the Size
of a Data Type
The sizeof operator gives size of any data
type or variable
double amount;
cout << "A float is stored in "
<< sizeof(float) << " bytesn";
cout << "Variable amount is stored in "
<< sizeof(amount) << " bytesn";
2-30

2.13 More on Variable
Assignments and Initialization
• Assigning value to a variable
– Assigns a value to a previously created variable
– A single variable name must appear on left side
of the = symbol
int size;
size = 5; // legal
5 = size; // not legal
2-31

Variable Assignment vs.
Initialization
• Initializing a variable
– Gives initial value to variable at time it is
created
– Can initialize some or all variables of
definition
int length = 12;
int width = 7, height = 5, area;
2-32

What if a variable is not initialized??
double amount;
cout << amount;
What happens?? …. It depends…
*Ignore - continues, repeats message
*Abort – program stops
*Retry – tries again then stops
- get MS “send error report?”
2-33

2.14 Scope
• The scope of a variable is that part of the
program where the variable may be used
• Scope of variable begins with definition,
continues through the block in which it is
defined
• A variable cannot be used before it is defined
int a;
cin >> a; // legal
cin >> b; // illegal
int b;
• (Test question)
2-34

Scope
To avoid problems…
• Define ALL variables & constants at the
beginning of the program!!!
• Later we will discuss other issues
related to scope.
2-35

2.15 Arithmetic Operators
• Used for performing numeric calculations
• C++ has unary, binary, and ternary
operators
– unary (1 operand) -5
– binary (2 operands) 13 - 7
– ternary (3 operands) exp1 ? exp2 : exp3
2-36

Binary Arithmetic
Operators
2-37
SYMBOL OPERATION EXAMPLE 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
Order of operation is standard mathematics.

/ Operator
• C++ division operator (/)performs integer
division if both operands are integers
cout << 13 / 5; // displays 2
cout << 2 / 4; // displays 0
• If either operand is floating-point, the result
is floating-point
cout << 13 / 5.0; // displays 2.6
cout << 2.0 / 4; // displays 0.5
2-38

% Operator - Modulus
• Same priority as * and /
• C++ modulus operator (%) computes the
remainder resulting from integer division
cout << 9 % 2; // displays 1
• % requires integers for both operands
cout << 9 % 2.0; // error
2-39

2.16 Comments
• Used to document parts of program
• Written for persons reading source code
of program
– Indicate purpose of program
– Describe use of variables
– Explain complex sections of code
• Ignored by compiler
• REQUIRED for all programs (by RH)
• No absolute rules, but STANDARDS 2-40

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;
2-41

Multi-Line Comments
• Begin with /* & end with */
• Can span multiple lines
/*----------------------------
Here's a multi-line comment
----------------------------*/
• Can be used as single-line comments
int area; /* Calculated area */
• MUST have both
2-42

Comment Guidelines
• Use your textbook as a GOOD Example
• Always comment with name, project name,
project description at beginning of every
program
• Descriptive comments within body of program
are REQUIRED
– If comment is so generic it could be moved to any
other program then it is not a “good comment”
– If comment states exactly what the codes says
then it is not a “good comment”
2-43

Chapter 2 Homework
• Checkpoints
– These are at the end of most sections (e.g. page
31). You should do all of these
• End of Chapter questions –
– Page 70+; All (1 – 27) 8E
• Quizzes will usually come from checkpoints &
end of chapter questions
2-44

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