how to assign a double double variable?

[仁义_许_]

if a double variable is assigned, d0 need to be tailed.

real(8)::a
a=1.2d0

Now, a higher precision variable need to be assigned, what is tailed?

real(16)::b
b=1.2??

[andrew_4619 · Accepted solution]

real(16)::b
b=1.2_16

! or better

integer, parameter :: rk = 16
real(rk) :: b
b = 1.2_rk

[Steve_Lionel]

Better still (and more portable):

Integer, parameter :: qk = selected_real_kind(30)
real(qk)::b
b=1.2_qk

[仁义_许_]

Steve Lionel (Ret.) wrote:

Better still (and more portable):

Integer, parameter :: qk = selected_real_kind(30)
real(qk)::b
b=1.2_qk

thx!!

Then, what forms of functions such as dsqrt is?

[mecej4]

仁义 许. wrote:
 Then, what forms of functions such as dsqrt is? 

DSQRT is a specific function (more than one function for one purpose, one for each type of argument). Fortran77 and earlier versions of Fortran had plenty of such specific functions. Fortran 90 and later versions provide generic functions, so that you can use a single function name regardless of the type of the argument and function value. It is recommended that you do not use specific functions such as DSQRT in new code.

[Steve_Lionel]

RIght - just use the generic SQRT.