I would like to know the reason for the difference in output between just_checking_1 and just_checking_2 in the below toy code. I guess this boils down to what is the difference between a(*) and a(:). Also, is there any way that subroutine just_checking_p could access the memory location to which b is pointing?

$ cat whereis.F90
program whereisit

integer, target :: a(100)
integer, pointer :: b(:)

print '("a is at 0x",Z8)', loc(a)
call just_checking_1(a)
call just_checking_2(a)

b => a
print '("b is at 0x",Z8)', loc(b)
call just_checking_p(b)

end program



subroutine just_checking_1(a)
integer :: a(*)     !<-- Noice: a(*)
print '("In just_checking_1 a is at 0x",Z8)', loc(a)
end subroutine


subroutine just_checking_2(a)
integer :: a(:)    !<-- Notice: a(:)
print '("In just_checking_2 a is at 0x",Z8)', loc(a)
end subroutine


subroutine just_checking_p(b)
integer, pointer, intent(in) :: b(:)
print '("In just checking b is at 0x",Z8)', loc(b)
end subroutine


$ ./a.out
a is at 0x  6B4140
In just_checking_1 a is at 0x  6B4140
In just_checking_2 a is at 0x       0
b is at 0x  6B4140
In just checking b is at 0x       0