2.9BSD - /usr/src/lib/libU77/test/sigtrtst.f

   1:         integer signal
   2:         external trap
   3:         isav = signal(8, 0, 1)
   4:         write(*,*) "1", signal(8, 0, 0)
   5:         write(*,*) "0", signal(8, trap, -1)
   6:         write(*,*) "addr", signal(8, 0, isav)
   7:         write(*,*) isav, signal(8, trap, -1)
   8:         x = 1.0/x
   9:         end
  10: 
  11:         subroutine trap(isig)
  12:         write(*,*) "Here I am."
  13:         end