2.3.2 Floating Point Type

Floating point numbers are the computer equivalent of scientific notation. The precise number of significant figures and the range of possible exponents is machine-specific; Emacs always uses the C data type double to store the value.

The printed representation for floating point numbers requires either a decimal point (with at least one digit following), an exponent, or both. For example, `1500.0', `15e2', `15.0e2', `1.5e3', and `.15e4' are five ways of writing a floating point number whose value is 1500. They are all equivalent.

See section 3. Numbers, for more information.