Randolph West continues a series on how SQL Server stores values:
As we know from before, integers are whole numbers, or numbers with no fractions (i.e. no decimal places). This is going to be in the test later, so pay attention. In other words, the numbers 0 through 9 are integers, but a floating point or decimal / numeric value is not an integer. As soon as you add decimal places, it stops being an integer even if the fraction equates to zero.
Inside the storage engine, integers are mostly signed values (they can have negative values), and each integer data type has a fixed size. The exception is
TINYINTwhich only has positive values. Like many other data types, integer types are stored byte-reversed (known as little-endian).
Click through for some good information from Randolph.