Fortran90 中引入的module 的语法，我感觉非常好用，以后争取把函数都用module 封装，丢弃common，这种封装的思想也能够使得编程很清晰，再来熟悉一下module的语法吧！

module constant
implicit none
real,parameter::pi=3.14159
end module constant

module var
implicit none
real :: t1,t2,t3
end module var

module  minu_add
use constant
implicit none
real :: t=pi
public add
public minu
contains
 subroutine add(x,y,res)
implicit none
real ,intent(in)::x
real ,intent(in)::y
real ,intent(out)::res

res=x+y-pi+t

return
end subroutine add

subroutine minu(x,y,res)
implicit none
real ,intent(in)::x
real ,intent(in)::y
real ,intent(out)::res
res=x-y-pi+t
return
end subroutine minu

end  module minu_add

program exe
use minu_add
use var
t1=1.0
t2=2.0
 call  add(t1,t2,t3)
 write(*,*)"add",t3
 call minu(t1,t2,t3)
 write(*,*)"minu",t3
  write(*,*)"ttt",t
stop
end program exe