What does “real*8” mean?

Question

The manual of a program written in Fortran 90 says, \"All real variables and parameters are specified in 64-bit precision (i.e. real*8).\"

According to

Answer 1

There are now at least 4 ways to specify precision in Fortran.

As already answered, real*8 specifies the number of bytes. It is somewhat obsolete but should be safe.

The new way is with "kinds". One should use the intrinsic functions to obtain the kind that has the precision that you need. Specifying the kind by specific numeric value is risky because different compilers use different values.

Yet another way is to use the named types of the ISO_C_Binding. This question discusses the kind system for integers -- it is very similar for reals.