What does 0.0_p2 mean?

Question

Please explain what does 0.0_p2 and 1.0_p2 mean here.

integer , parameter :: sp = kind(1.0)
integer , parameter :: p2 = selected_real_kind(2*precision(1.0_sp))

real(p2), parameter :: zero = 0.0_p2, &
                       one = 1.0_p2

Answer 1

The term

0.0_p2

is the real number 0.0 with kind p2. The snippet you've posted tells us that p2 denotes the kind returned by the expression

selected_real_kind(2*precision(1.0_sp))

so p2 is probably the same as double precision, and also probably a 64-bit real number.