|2.18.1.Floating Point variables|
The numbers 5.5, 8.3, and -12.6 are all floating-point numbers.
Floating-point numbers must contain a decimal point.
So 5.0 is a floating-point number, while 5 is an integer.
You could omit digits before the decimal point and specify a number as .5 instead of 0.5
A floating-point zero should be written as 0.0.
The floating-point number may include an exponent specification of the form:e + exp
For example, 1.2e34 is a shorthand version of 1.2*10^34.