program Calendar;
{Reads the day of January 1 and the year and prints calendar.
  Demo for stubs, drivers, and enumerated types.}

type DayType = (Sun, Mon, Tue, Wed, Thur, Fri, Sat);
     WeekdayType = Mon..Fri;
     MonthType = (Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec);
     YearType = 1500..2500; {valid for Gregorian calendar}

var  Year : Yeartype; {input - the calendar year}
     StartDay : Daytype; {input - New Year's Day}
     DayCh1,DayCh2,DayCh3 : Char; {input - letters in day name}
     Month : MonthType; {the current month}
     FebFlag : Boolean; {true for leap years}

function LeapYear(YearFP : YearType) : Boolean;
{determine if leap year; details needed}
     begin
       LeapYear := YearFP mod 4 = 0;
       if ((YearFp mod 100) = 0)) and ((YearFP mod 400) <> 0) then
         LeapYear := False;
     end;

procedure Heading(YearFP : YearType);
{stub - to output nice heading}
     begin
       WriteLn('Heading for year  ', YearFP);
     end;

procedure DayCode(Ch1,Ch2: Char; var Day : DayType);
{stub of day conversion - returns Sun or Mon}
     begin
       case Ch1 of
        'S' : Day := Sun
       else
        Day := Mon
       end{case Ch1};
     end;

procedure PrintMonth(Month: MonthType; var StDay : DayType);
{the main procedure}
  var ML : 28..31;

     begin
       {MonthHeading(Month);
       ML := MonLen(Month);
       PrintWeeks(ML, StDay)}
     end;

begin{main program}
     WriteLn('Type the year - after 1500, before 2500 - and New Year''s Day');
     WriteLn('Use the first 3 letters to identify the day.');
     ReadLn(Year, DayCh1, DayCh2, DayCh3);
     if LeapYear(Year) then
       FebFlag := True
     else
       FebFlag := False;
     Heading( Year );
     DayCode(DayCh1,DayCh2,StartDay);
     for Month := Jan to Dec do
       PrintMonth(Month,StartDay);
end.