Variables in C

In the C language, a variable is a named memory location used to store data in a program. Variables are used when we need to store, change, or perform calculations on data in a program. A data type is used to specify the type of data that a variable will store.

A variable in C is a location in memory used to store a specific type of data. It has a name through which we can access that memory location. It is called a variable because its value can change. Variables must be declared before use with a specific data type.

Local Variable: Declared inside a specific function or block and can only be used within that scope.

Global Variable: Valid throughout the entire program and is declared outside any function.

Static Variable: Retains its value throughout the program, even if declared within a function.

Extern Variable: Used when we need to share a variable across multiple files.

Automatic Variable: Declared inside a function or block and are valid only during its execution. This is the default type for local variables.

The main data types in C are `int` (integers), `float` (decimal numbers), `char` (single characters), and `double` (large decimal numbers).

Values can be changed dynamically, calculations are made easier, proper naming makes code easier to understand, and it provides flexibility.