Variables

In programming, a variable is a container (storage area) to hold data.

To indicate the storage area, each variable should be given a unique name (identifier). Variable names are just the symbolic representation of a memory location. For example:

int playerScore = 95;

Here, playerScore is a variable of int type. Here, the variable is assigned an integer value 95.

The value of a variable can be changed, hence the name variable.

char ch = 'a';
// some code
ch = 'l';

Rules for naming a variable

1. A variable name can only have letters (both uppercase and lowercase letters), digits and underscore.
2. The first letter of a variable should be either a letter or an underscore.
3. There is no rule on how long a variable name (identifier) can be. However, you may run into problems in some compilers if the variable name is longer than 31 characters.

Note: You should always try to give meaningful names to variables. For example: firstName is a better variable name than fn.

C is a strongly typed language. This means that the variable type cannot be changed once it is declared. For example:

int number = 5;      // integer variable
number = 5.5;        // error
double number;       // error

Here, the type of number variable is int. You cannot assign a floating-point (decimal) value 5.5 to this variable. Also, you cannot redefine the data type of the variable to double. By the way, to store the decimal values in C, you need to declare its type to either double or float.