/******************************************************/
/* This program computes either the present value(PV),*/
/* the payment(PMT), or the number of periods in an   */
/* annuity.                                           */
/******************************************************/
annuity:
    procedure options(main);
    %replace
       clear by '^z',
       true  by '1'b;
    declare 
       PMT fixed decimal(7,2),
       PV  fixed decimal(9,2),
       IP  fixed decimal(6,6),
       x   float binary,
       yi  float binary,
       i   float binary,
       n   fixed;
  
    declare 
       ftc entry(float binary(24)) 
           returns(character(17) varying);
  
    put list (clear,'^i^iO R D I N A R Y   A N N U I T Y');
    put skip(2) list
    ('^iEnter Known Values, or 0, on Each Iteration');
  
    on error
       begin;
         put skip list('^iInvalid Data, Re-enter');
         goto retry;
       end;
  
    retry:
    do while (true);
       put skip(3) list('^iPresent Value ');
       get list(PV);
       put list('^iPayment       ');
       get list(PMT);
       put list('^iInterest Rate ');
       get list(yi);
       i = yi / 1200;
       put list('^iPay Periods   ');
       get list(n);
  
       if PV = 0 | PMT = 0 then
          x = 1 - 1/(1+i)**n;
  
       /******************************/
       /* compute the present value  */
       /******************************/
       if PV = 0 then
          do;
            PV = PMT * dec(ftc(x/i),15,6);
            put edit('^iPresent Value is ',PV)
                    (a,p'$$$,$$$,$$$V.99');
          end;
  
       /******************************/         
       /*    compute the payment     */
       /******************************/
        if PMT = 0 then
           do;
             PMT = PV * dec(ftc(i/x),15,8);
             put edit('^iPayment is ',PMT)
                     (a,p'$$,$$$,$$$V.99');
           end;
  
       /*****************************/
       /* compute number of periods */
       /*****************************/
       if n = 0 then
          do;
            IP = ftc(i);
            x = char(PV * IP / PMT);
            n = ceil ( - log(1-x)/log(1+i) );
            put edit('^i',n,' Pay Periods')
                    (a,p'ZZZ9',a);
          end;
    end;
  
end annuity;