It can be written in two forms - Fractional form and Exponential form.
For fractional form:
Must have at least one digit.
It must have a decimal point.
It could be either positive or negative (Default : positive).
No commas or blanks allowed.
Eg: +320.13 ; 240.0 ; -567.9
For exponential form:
The mantissa and exponential part are separated by the letter ‘e’.
The mantissa and exponent part can be positive or negative.
The exponent must have at least one digit.
Range is -3.4e38 to 3.4e38.
+3.1e-2 ;-2.5e+4 ; -0.4e+2.