GNU Emacs supports two numeric data types: *integers* and
*floating-point numbers*. Integers are whole numbers such as
−3, 0, 7, 13, and 511. Floating-point numbers are numbers with
fractional parts, such as −4.5, 0.0, and 2.71828. They can
also be expressed in exponential notation: ‘`1.5e2`’ is the same as
‘`150.0`’; here, ‘`e2`’ stands for ten to the second power, and
that is multiplied by 1.5. Integer computations are exact.
Floating-point computations often involve rounding errors, as the
numbers have a fixed amount of precision.