| Digital
Reference---Introduction to Variables
Types
Do you recall variables from your mathematics
class? Well, in C++, variables are used in a similar manner. They
represent values that are assigned to them. There are many kinds
of variables. Here are some common ones:
int
int variables represent integer values that have
an absolute value less than or equal to 32,767
double
double variables represent values that have a
decimal point
long
long variables represent integer values that
have an absolute value less than or equal to 2,147,483,647
char
char variables represent characters
bool
bool variables represent true or false; #include
<bool.h> must be included in the preprocessor
Variable Assignments
To assign values to variables, give the type of
variable and the variable name (also called the identifier). Here’s
an example:
Let’s introduce an integer variable x:
int x;
x = 168;
Above we have just assigned the value 168 to the
integer variable x.
An example assigning a number with a decimal to
a variable:
double y;
y = 168.28;
Here the decimal value 168.28 is assigned to the
double variable y.
Assigning a character to a variable:
char someletter;
someletter = `A’;
The letter A is assigned to the char variable
someletter.
The name of the variable (a.k.a. identifier)
needs to begin with a letter. It can consist of any letter,
number, and the underscore. The length of the identifier is up to
you!
Now we will show you what operators can be used
to allow your program to do arithmetic calculations.
For addition, use +
For subraction, use –
For multiplication, use *
For division, use /
If you want to find the remainder from division,
use the % symbol. This is called modulus division.
Whenever you perform calculations between two
integers, you will have an integer result. This is likewise
between two double values, resulting in a double value.
However, if you have an integer and a double
value in a calculation, the result will be a double.
Logical Operators
&& and || are logical operators.
&& symbolizes "and" in C++. || symbolizes
"or."
These logical operators connect Boolean
expressions (expressions that are either true or false) together
and can be used in the if statements, if-else statements, switch
statements, do-while, and while statements, which will all be
discussed later.
Here is a table showing the result of two
Boolean expressions connected by logical operators:
EXPRESSIONS RESULTS
|
TRUE && TRUE |
TRUE |
|
TRUE || TRUE |
TRUE |
|
TRUE || FALSE |
TRUE |
|
FALSE || TRUE |
TRUE |
|
FALSE && FALSE |
FALSE |
|
FALSE || FALSE |
FALSE |
|
TRUE && FALSE |
FALSE |
|
FALSE && TRUE |
FALSE |
NEXT |