Floating Point Types

If you use the literal 197.0 in a program, the decimal point tells the compiler to represent the value using a floating point primitive data type. The bit pattern used for floating point 197.0 is very much different than that used for the integer 197. Recall the two floating point primitive types:

Floating Point Primitive Data Types
Type	Size	Range
float	32 bits	-3.4E+38 to +3.4E+38
double	64 bits	-1.7E+308 to 1.7E+308

Data type float is sometimes called "single-precision floating point". This vocabulary comes from the language FORTRAN, at one time the dominant programming language. Data type double has twice as many bits and is sometimes called "double-precision floating point".

In programs, floating point literals have a decimal point in them, and no commas:

123.0        -123.5         -198234.234       0.00000381

Note: Literals written like the above will automatically be of type double. Almost always, if you are dealing with floating point numbers you should use variables of type double. Then the data type of literals like the above will match the data type of your variables. Data type float should be used only for special circumstances (such as when you need to process a file of data containing 32 bit floats).