"EDUCATION IS NOT THE PREPRATION OF LIFE
EDUCATION IS LIFE ITSELF"

Variables:
If you declare a variable in C (later on we talk about how to do this), you ask the operating system for a piece of memory. This piece of memory you give a name and you can store something in that piece of memory (for later use). There are two basic kinds of variables in C which are numeric and character.


Numeric variables:
Numeric variables can either be of the type integer (int) or of the type real (float). Integer (int) values are whole numbers (like 10 or -10). Real (float) values can have a decimal point in them. (Like 1.23 or -20.123).


Character variables:
Character variables are letters of the alphabet, ASCII characters or numbers 0-9. If you declare a character variable you must always put the character between single quotes (like so ‘A’ ). So remember a number without single quotes is not the same as a character with single quotes.
Constants:

The difference between variables and constants is that variables can change their value at any time but constants can never change their value. (The constants value is lockedfor the duration of the program). Constants can be very useful, Pi for instance is a good example to declare as a constant.



Data Types:
So you now know that there are three types of variables: numeric – integer, numeric-real and character. A variable has a type-name, a type and a range (minimum / maximum). In the following table you can see the type-name, type and range:

Type-name                               Type                                          Range

int                               Numeric – Integer                               -32 768 to 32 767
short                           Numeric – Integer                               -32 768 to 32 767
long                             Numeric – Integer                                -2 147 483 648 to 2 147 483 647
float                             Numeric – Real                                   1.2 X 10-38 to 3.4 X 1038
double                          Numeric – Real                                    2.2 X 10-308 to 1.8 X 10308
char                             Character                                            All ASCII characters

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