BEGIN
   TEXT PROCEDURE REV(S); TEXT S;
   BEGIN
       TEXT T;
       INTEGER L,R;
       T :- COPY(S);
       L := 1; R := T.LENGTH;
       WHILE L < R DO
       BEGIN
           CHARACTER CL,CR;
           T.SETPOS(L); CL := T.GETCHAR;
           T.SETPOS(R); CR := T.GETCHAR;
           T.SETPOS(L); T.PUTCHAR(CR);
           T.SETPOS(R); T.PUTCHAR(CL);
           L := L+1;
           R := R-1;
        END;
        REV :- T;
   END REV;

   TEXT INP;
   INP :- "asdf";

   OUTTEXT(INP);      OUTIMAGE;
   OUTTEXT(REV(INP)); OUTIMAGE;
END