From what i have read, a value of data type double has an approximate precision of 15 decimal places.However, when i use a number whose decimal representation repeats, such as 1. 0/7. 0, i find thaA double in java is the class version of the double basic type - you can use doubles but, if you want to do something with them that requires them to be an object (such as put them in a collection), you'll.Format %lf in printf was not supported in old (pre-c99) versions of c language, which created superficial inconsistency between format specifiers for double in printf and scanf.The long double function prototypes are identical to the prototypes for their double counterparts, except that the longdouble data type replaces the double data type.The long double versions of these.