program my_main
      write(*,*)'Type in your number, please:'
      read(*,*) a
      call sub1(a,b)
      write(*,*)'Main_Program (1) :',b,'is what I got.'
      call sub2(a,b)
      write(*,*)'Main_Program (2) :',b,'is what I got.'
      call sub3(a,b)
      write(*,*)'Main_Program (3) :',b,'is what I got.'
      end

      subroutine sub1(a_in,a_out)
      a_out = a_in * a_in
c     return
      end

      subroutine sub2(a_in,a_out)
      a_out = sqrt(a_in)
c     return
      end

      subroutine sub3(a_in,a_out)
      a_out = a_in * a_in * a_in
c     return
      end