turingmaschine-schoening-p83.cob   Interaktion und
PortierbarkeitCobol

       identification division.
       program-id. turing is common initial.
       author. "JD".
       date-written. 25.10.2004.
       date-compiled.
       data division.
       working-storage section.
        77 card       pic 9(4) value 3.
        77 leftband   pic 9(16) value 0.
        77 head       pic 9(1).
        77 state      pic 9(16).
          88 startstate       value 0.
        77 endstate  pic 9(16).
          88                   value 3.
       linkage section.
        77 rightband pic 9(16).
       procedure division using reference rightband.
      **********************************************
      *simuliert eine Turing Maschine
      *   Bandalphabet   als Integer mit Kardinalität card
      *   Eingbealphabet als Integer mit Kardinalität card
      *   rechtes Band   als Integer mit Basis card(Alphabet)
      *   linkes  Band   als Integer mit Basis card(Alphabet)
      *   Zustand        als Integer
      **********************************************
         display "start"
      * check rightband for input alphabet obmitted
         set startstate to true
         perform until (state=endstate)
          compute head=function mod(rightband,card)
           evaluate true
           when state=0
             if      head=0 then move 0 to state perform 0right
             else if head=1 then move 1 to state perform 1right
             else if head=3 then move 1 to state perform bleft
           when state=1
             if      head=0 then move 2 to state perform 1left
             else if head=1 then move 1 to state perform 0left
             else if head=3 then move 3 to state
           when state=2
             if      head=0 then move 2 to state perform 0left
             else if head=1 then move 2 to state perform 1left
             else if head=3 then move 3 to state perform bright
           when state=endstate
             display "ende, Leftband="leftband" Rightband="rightband
           end-evaluate
         end-perform.
         goback.
        0left.
         compute leftband=leftband/card
         compute rightband=rightband*card
        1left.
         compute leftband=leftband/card
         compute rightband=rightband*card+1
        bleft.
         compute leftband=leftband/card
         compute rightband=rightband*card+2
        0right.
         compute leftband=leftband*card  
         compute rightband=rightband/card
        1right.
         compute leftband=leftband*card 
         compute rightband=rightband/card+1
        bright.
         compute leftband=leftband*card 
         compute rightband=rightband/card+2
        end-program turing.