THE SIZE OF A VARIABLE
The size of a variable is the number of memory spaces it can accept, determined by the kind of data it can store. So when you declare a variable of the type float, your computer automatically allocates memory or a cell of the size 4 bytes, extending to other data types.

SIZES OF DIFFERENT KINDS OF VARIABLES

INTEGER VARIABLES:
Short Integer - 2 bytes - 16 bits.
Integer - 4 bytes - 32 bits.

FLOATING-POINT VARIABLES:
Float - 4 bytes - 32bits.
Double - 8 bytes - 64bits.
Long Double - 10 bytes - 80bits.

NON NUMERICAL VARIABLE:
Character - 1 byte - 8bits.
Object - Determined by the number of attributes in the class of an object.
String - Determined by the number of characters in the string.

STATIC VERSUS DYNAMIC
In statically written languages, we can stipulate the kind of data or values our variables can pack (Declaration of variables) as opposed to dynamically written languages in which the type of data a variable can accept is determined by the initial value it takes. We do not declare variables in some dynamically written languages.

WHAT HAPPENS WHEN I DECLARE A VARIABLE?
In statically written programming languages (Java, C, C++, C#, etc), when a variable is declared, a cell is automatically allocated for the variable. In most cases (language-dependent), the allocated cell or space may contain a garbage value; this value is a result of other programs utilizing that particular memory cell or space and releasing it when terminated without proper deallocation. And this is where INITIALIZATION comes in. INITIALIZATION is the act of assigning a variable its initial value. We can use INITIALIZATION to reset the values or bits in the memory cell.