Integer,Long,Double,Decimal

To store numaric values in variables declare variables with one of  the numaric data types Integer ,Long,Double and Decimal.

Integer:

A 32-bit number that doesn't include a decimal point .
Integers have a minimum value of  -2,147,483,648 and a maximum value of 2,147,483,647

Ex:Integer i=1;

Double:

Anumber that includes a deciamal point .

Decimal is an orbitary precision numbers .Currency fields are automatically assigned precission numbers. Currency fields are automatically assigned the type deciamal

Ex: Double d = 3.14159;

Long :

A 64 bit number that doesn't include a decimal point longs have a minimum value of -263 and maximum value of 263-1

Ex: Long l = 2147483648l;

Decimal : A number that includes a decimal point.

decimal is an orbitary precision number

Currency fields are automatically assigned the type deciaml.

Deciaml d = 19.23;

Null values :

If we declare a varible and don't initilize it with a value , it will be null. Null means the absense of a value. We can also assign a null to varivle  declare with a primitive type.

Both of these statements results in a varible set to null

Boolean x = null;
Decimal d;