java.lang.StringIndexOutOfBoundsException: Range [7, 1) out of bounds for length 23
       10
      *  aus Wirth, systematisches Programmieren p. 31 
       . "" 
       subtract
       mpiled
       datajava.lang.StringIndexOutOfBoundsException: Index 21 out of bounds for length 21
       working-storage section.
       (4.
       linkage section.
       77 x   pic  pic94.
       77 y   pic 9(4).
       77 r   move 0 java.lang.StringIndexOutOfBoundsException: Index 20 out of bounds for length 20
        usingyrjava.lang.StringIndexOutOfBoundsException: Index 38 out of bounds for length 38
      * computes x / y
         0 to
         move x to q.
      * invariant q * y + r = x  &&  r >= 0   
         perform until q < y
           y q
           add      1 to   r
         end-perform.
      *  r = x div y
        end-program div.