PROGRAM hat;

{  This program displays on the IBM graphics screen a plot of the 'hat'
{  function.  The hat is displayed in the hi-resolution mode.
{
{  The program was written for Turbo Pascal.  It uses an external routine
{  to perform the plot function.  This routine is held in file POINT.BIN.
{  You must have set the disk default to the drive with POINT.BIN before
{  compiling the program.
{
{  NOTE -- This program will take about an hour to run if you do not have
{  an 8087 chip running with Turbo Pascal-8087 v2.0.  If you do have that
{  hardware/software configuration, the program will run in under three minutes.
{  You cannot halt the program with a BREAK command.  You have to warm boot
{  (CONTROL-ALT-DEL) the IBM.}


CONST
  p = 310;
  q = 95;
  xp = 180;
  yp = 50;
  zp = 64;

VAR
  yf,xy,zf,xf,zt,xt,xr,yr,yy,xpzp : REAL;
  xp2,zi,zzp,zzq,xl,xi,yi         : INTEGER;
  qq, a, zz, xx, x1, y1           : INTEGER;
  aa                              : STRING[100];

      TYPE
        varX = RECORD
          varL,varH: BYTE;
        END;
        TimeRec = RECORD
          AX,BX: varX;
          Min,Hour,Msec,Sec: BYTE;
          BP,SI,DI,DS,ES,FLAGS: INTEGER;
        END;
        RecPack = RECORD
          AX: varX;
          BX,CX,DX,BP,SI,DI,DS,ES,FLAGS: INTEGER;
        END;

      VAR
        intparm : RecPack;
        i,j : INTEGER;
        rx,ry : INTEGER;


      PROCEDURE ShowTime;
      VAR
        timeparm : TimeRec;

      BEGIN
        WITH TimeParm DO
          BEGIN
            AX.varH := $2C;
            MsDos(timeparm);
            WRITELN('Time is : ',Hour,':',Min,':',Sec,'.',Msec);
          END;
      END;



BEGIN
  qq := 2 * q;
  xr := 1.5*PI;
  xf := xr/xp;
  xpzp := xp/zp;
  xp2 := xp*xp;
  yr := 1;
  yf := yp/yr;
  zf := xr/zp;

  ShowTime;
  HIRES; HiresColor(7);
  ShowTime;
  FOR zi:= -q TO q-1 DO
    BEGIN
      IF (zi >= -zp) AND (zi <= zp) THEN
        BEGIN
          zt := zi * xpzp;
          zz := zi;
          xl := TRUNC (0.5 + SQRT(xp2 - zt*zt));
          FOR xi := - xl TO xl DO
            BEGIN
              xt := SQRT(xi*xi + zt*zt) * xf;
              yy := (SIN(xt) + 0.4 * SIN(3 * xt)) * yf;
              x1 := ROUND(xi + zz + p);
              y1 := ROUND(qq - (yy - zz + q));
              PLOT(x1,y1,1);
            END;
        END; {if}
  END; {next zi}

  GOTOXY(1,2);
  ShowTime;
  READLN(aa);
  CRTINIT;
  ShowTime;

END.
  13 5-8  5 1-8 Int   Harvest    * * 5965  