In This Chapter
Declaring different types of variables
Using floating-point variables
Declaring and using other variable types
The most fundamental of all concepts in C++ is the variable— a variable is like a small box. You can store things in the box for later use, particularly numbers. The concept of a variable is borrowed from mathematics. A statement such as
x = 1
stores the value 1 in the variable
x. From that point forward, the mathematician can use the variable
x in place of the constant 1 — until he changes the value of
x to something else.
Variables work the same way in C++. You can make the assignment
x = 1;
From that point forward in the execution of the program, until the value of x is changed, the value of x is 1. References to x are replaced by the value 1. In this chapter, you will find out how to declare and initialize variables in C++ programs. You will also see the different types of variables that C++ defines and when to use each.
A mathematician might write something like the following:
(x + 2) = y / 2 x + 4 = y solve for x and y
Any reader who's had algebra realizes right off that the mathematician has introduced the variables
y. But C++ isn't that smart. (Computers may be fast, but they're stupid.)
You have to announce each variable to C++ before you can use it. You have to say something soothing like this:
int x; x = 10; int y; y = 5;
These lines of code declare that a variable
x exists, ...