Can you explain further about what you mean by internal representation? As far as the SQL is concerned a data type is an attribute that specifies the type of data that the object can hold: integer data, character data, monetary data, date and time data, binary strings, and so on. As BOL too: SQL Server supplies a set of system data types that define all the types of data that can be used with SQL Server. You can also define your own data types in Transact-SQL or the Microsoft .NET Framework. Alias data types are based on the system-supplied data types.
I read that float is stored as binary and decimal, numeric is stored as number itself. So I want to learn how the value of each datatype is stored(Structured).
i think to understand it more clearly you should read data structure and c language. It gives good information about data type and their design. Not sure how this forum can help you in this as its related to your own reading.
Ok that gives bit more information, as you are aware SQL Server has variety of datatypes and more options you have that are confusing & misunderstanding arise from data type limitations rather than functionality. Here is the table list that can clarify few of your doubts which is extracted from SQL Server Books Online:Character data types Data TypeLengthStorage SizeMax CharactersUnicode charFixedAlways n bytes8,000No; each character requires 1 byte varcharVariableActual length of entry in bytes8,000No; each character requires 1 byte ncharFixedTwice n bytes4,000Yes; each character requires 2 bytes nvarcharVariableTwice actual length of entry in bytes4,000Yes; each character requires 2 bytes Integer data types Data typeMinimum valueMaximum valueStorage size tinyint02551 byte smallint-32,76832,7672 bytes int-2,147,483,6482,147,483,6744 bytes bigint-9,223,372,036,854,775,8089,223,372,036,854,775,8078 bytes Precision storage requirements Total characters (precision)Storage size 1 - 95 bytes 10 - 199 bytes 20 - 2813 bytes 29 - 3817 bytesFloat and real data type restrictions Data typenMinimum ValueMaximum valuePrecisionStorage size float(n)1 - 24-1.79E + 3081.79 + 3087 digits4 bytes 25 - 53-1.79E + 3081.79E + 30815 digits8 bytes realn/a-3.40E + 383.40E + 387 digits4 bytes Smalldatetime and datetime restrictions Data typeMinimum valueMaximum valueAccuracyStorage size smalldatetimeJanuary 1, 1900June 6, 2079Up to a minute4 bytes (the first 2 bytes store the date; the second 2 bytes store the time) datetimeJanuary 1, 1753December 31, 9999One three-hundredth of a second8 bytes (the first 4 bytes store the date; the second 4 bytes store the time)Smallmoney and money restrictions Data typeMinimum valueMaximum valueStorage size smallmoney-214,748.3648214,748,36474 bytes money-922,337,203,685,477.5808922,337,203.685,477.58078 bytes In addition to the above SQL Server 2008 gets new data types, date/time/datetime2/datetimeoffset/hierarcyid/spatial, for more information on these types BOL is your best friend http://sqlserver-qa.net/blogs/sql2008/archive/2009/02/04/5391.aspx fyi.