C++ Crash Course: a fast-Paced Introduction

Bootstrapping C++ 
This section gives you just enough context to support the example code in 
the chapters to come. You’ll have questions about the details, and the com-
ing chapters will answer them. Until then, don’t panic!
The C++ Type System
C++ is an object-oriented language. Objects are abstractions with state and 
behavior. Think of a real-world object, such as a light switch. You can describe 
its state as the condition that the switch is in. Is it on or off? What is the maxi-
mum voltage it can handle? What room in the house is it in? You could also 

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14
Chapter 1
describe the switch’s behavior. Does it toggle from one state (on) to another 
state (off)? Or is it a dimmer switch, which can be set to many different states 
between on and off? 
The collection of behaviors and states describing an object is called its 
type. C++ is a strongly typed language, meaning each object has a predefined 
data type.
C++ has a built-in integer type called 
int
. An 
int
object can store whole 
numbers (its state), and it supports many math operations (its behavior).
To perform any meaningful tasks with 
int
types, you’ll create some 
int
objects and name them. Named objects are called variables.
Declaring Variables
You declare variables by providing their type, followed by their name, fol-
lowed by a semicolon. The following example declares a variable called 
the_answer
with type 
int
:
int
u
the_answer
v
;
The type, 
int
u
, is followed by the variable name, 
the_answer
v
.
Initializing a Variable’s State
When you declare variables, you initialize them. Object initialization establishes 
an object’s initial state, such as setting its value. We’ll delve into the details of 
initialization in Chapter 2. For now, you can use the equal sign (
=
) following a 
variable declaration to set the variable’s initial value. For example, you could 
declare and assign 
the_answer
in one line:
int the_answer = 42;
After running this line of code, you have a variable called 
the_answer
with type 
int
and value 42. You can assign variables equal to the result of 
math expressions, such as:
int lucky_number = the_answer / 6;
This line evaluates the expression 
the_answer / 6
and assigns the result 
to 
lucky_number
. The 
int
type supports many other operations, such as addi-
tion 
+
, subtraction 
-
, multiplication 
*
, and modulo division 
%
.
N O T E
 
If you aren’t familiar with modulo division or are wondering what happens when you 
divide two integers and there’s a remainder, you’re asking great questions. And those 
great questions will be answered in detail in Chapter 7.

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