double and accuracy

Question

Using long double I get 18/19 = 0.947368421052631578..., and 947368421052631578 is the repeating decimal. Using double I

Answer 1

A double typically provides 16(±1) decimal digits. Your example shows this:

     4   8  12  16
     v   v   v   v
0.947368421052631578 long double
0.947368421052631526 double

The answers agree to 16 digits. This is what should be expected. Also note that there's no guarantee in the C Standard that a long double has more precision than a double.