求注释  
/*
   GRAPHICS DEMO FOR TURBO C 2.0

   Copyright (c) 1987,88 Borland International. All rights reserved.

   From the command line, use:

        tcc bgidemo graphics.lib

*/

#ifdef __TINY__
#error BGIDEMO will not run in the tiny model.
#endif

#include <dos.h>
#include <math.h>
#include <conio.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>

#include <graphics.h>

#define ESC    0x1b            /* Define the escape key    */
#define TRUE    1            /* Define some handy constants    */
#define FALSE    0            /* Define some handy constants    */
#define PI    3.14159         /* Define a value for PI    */
#define ON    1            /* Define some handy constants    */
#define OFF    0            /* Define some handy constants    */

char *Fonts[] = {
  "DefaultFont",   "TriplexFont",   "SmallFont",
  "SansSerifFont", "GothicFont"
};

char *LineStyles[] = {
  "SolidLn",  "DottedLn",  "CenterLn",  "DashedLn",  "UserBitLn"
};

char *FillStyles[] = {
  "EmptyFill",  "SolidFill",      "LineFill",      "LtSlashFill",
  "SlashFill",  "BkSlashFill",    "LtBkSlashFill", "HatchFill",
  "XHatchFill", "InterleaveFill", "WideDotFill",   "CloseDotFill"
};

char *TextDirect[] = {
  "HorizDir",  "VertDir"
};

char *HorizJust[] = {
  "LeftText",   "CenterText",   "RightText"
};

char *VertJust[] = {
  "BottomText",  "CenterText",  "TopText"
};

struct PTS {
  int x, y;
};    /* Structure to hold vertex points    */

int    GraphDriver;        /* The Graphics device driver        */
int    GraphMode;        /* The Graphics mode value        */
double AspectRatio;        /* Aspect ratio of a pixel on the screen*/
int    MaxX, MaxY;        /* The maximum resolution of the screen */
int    MaxColors;        /* The maximum # of colors available    */
int    ErrorCode;        /* Reports any graphics errors        */
struct palettetype palette;        /* Used to read palette info    */

/*                                    */
/*    Function prototypes                        */
/*                                    */

void Initialize(void);
void ReportStatus(void);
void TextDump(void);
void Bar3DDemo(void);
void RandomBars(void);
void TextDemo(void);
void ColorDemo(void);
void ArcDemo(void);
void CircleDemo(void);
void PieDemo(void);
void BarDemo(void);
void LineRelDemo(void);
void PutPixelDemo(void);
void PutImageDemo(void);
void LineToDemo(void);
void LineStyleDemo(void);
void CRTModeDemo(void);
void UserLineStyleDemo(void);
void FillStyleDemo(void);
void FillPatternDemo(void);
void PaletteDemo(void);
void PolyDemo(void);
void SayGoodbye(void);
void Pause(void);
void MainWindow(char *header);
void StatusLine(char *msg);
void DrawBorder(void);
void changetextstyle(int font, int direction, int charsize);
int  gprintf(int *xloc, int *yloc, char *fmt, ... );

/*                                    */
/*    Begin main function                        */
/*                                    */

int main()
{

  Initialize();         /* Set system into Graphics mode    */
  ReportStatus();        /* Report results of the initialization */

  ColorDemo();            /* Begin actual demonstration        */
  if( GraphDriver==EGA || GraphDriver==EGALO || GraphDriver==VGA )
    PaletteDemo();
  PutPixelDemo();
  PutImageDemo();
  Bar3DDemo();
  BarDemo();
  RandomBars();
  ArcDemo();
  CircleDemo();
  PieDemo();
  LineRelDemo();
  LineToDemo();
  LineStyleDemo();
  UserLineStyleDemo();
  TextDump();
  TextDemo();
  CRTModeDemo();
  FillStyleDemo();
  FillPatternDemo();
  PolyDemo();
  SayGoodbye();         /* Give user the closing screen     */

  closegraph();         /* Return the system to text mode    */
  return(0);
}

/*                                    */
/*    INITIALIZE: Initializes the graphics system and reports     */
/*    any errors which occured.                    */
/*                                    */

void Initialize(void)
{
  int xasp, yasp;            /* Used to read the aspect ratio*/

  GraphDriver = DETECT;         /* Request auto-detection    */
  initgraph( &GraphDriver, &GraphMode, "" );
  ErrorCode = graphresult();        /* Read result of initialization*/
  if( ErrorCode != grOk ){        /* Error occured during init    */
    printf(" Graphics System Error: %s\n", grapherrormsg( ErrorCode ) );
    exit( 1 );
  }

  getpalette( &palette );        /* Read the palette from board    */
  MaxColors = getmaxcolor() + 1;    /* Read maximum number of colors*/

  MaxX = getmaxx();
  MaxY = getmaxy();            /* Read size of screen        */

  getaspectratio( &xasp, &yasp );    /* read the hardware aspect    */
  AspectRatio = (double)xasp / (double)yasp; /* Get correction factor    */

}

/*                                    */
/*    REPORTSTATUS: Report the current configuration of the system    */
/*    after the auto-detect initialization.                */
/*                                    */

void ReportStatus(void)
{
  struct viewporttype      viewinfo;    /* Params for inquiry procedures*/
  struct linesettingstype lineinfo;
  struct fillsettingstype fillinfo;
  struct textsettingstype textinfo;
  struct palettetype      palette;

  char *driver, *mode;            /* Strings for driver and mode    */
  int x, y;

  getviewsettings( &viewinfo );
  getlinesettings( &lineinfo );
  getfillsettings( &fillinfo );
  gettextsettings( &textinfo );
  getpalette( &palette );

  x = 10;
  y = 4;

  MainWindow( "Status report after InitGraph" );
  settextjustify( LEFT_TEXT, TOP_TEXT );

  driver = getdrivername();
  mode = getmodename(GraphMode);    /* get current setting        */

  gprintf( &x, &y, "Graphics device    : %-20s (%d)", driver, GraphDriver );
  gprintf( &x, &y, "Graphics mode      : %-20s (%d)", mode, GraphMode );
  gprintf( &x, &y, "Screen resolution  : ( 0, 0, %d, %d )", getmaxx(), getmaxy() );

  gprintf( &x, &y, "Current view port  : ( %d, %d, %d, %d )",
  viewinfo.left, viewinfo.top, viewinfo.right, viewinfo.bottom );
  gprintf( &x, &y, "Clipping           : %s", viewinfo.clip ? "ON" : "OFF" );

  gprintf( &x, &y, "Current position   : ( %d, %d )", getx(), gety() );
  gprintf( &x, &y, "Colors available   : %d", MaxColors );
  gprintf( &x, &y, "Current color      : %d", getcolor() );

  gprintf( &x, &y, "Line style         : %s", LineStyles[ lineinfo.linestyle ] );
  gprintf( &x, &y, "Line thickness     : %d", lineinfo.thickness );

  gprintf( &x, &y, "Current fill style : %s", FillStyles[ fillinfo.pattern ] );
  gprintf( &x, &y, "Current fill color : %d", fillinfo.color );

  gprintf( &x, &y, "Current font       : %s", Fonts[ textinfo.font ] );
  gprintf( &x, &y, "Text direction     : %s", TextDirect[ textinfo.direction ] );
  gprintf( &x, &y, "Character size     : %d", textinfo.charsize );
  gprintf( &x, &y, "Horizontal justify : %s", HorizJust[ textinfo.horiz ] );
  gprintf( &x, &y, "Vertical justify   : %s", VertJust[ textinfo.vert ] );

  Pause();                /* Pause for user to read screen*/

}

/*                                    */
/*    TEXTDUMP: Display the all the characters in each of the     */
/*    available fonts.                        */
/*                                    */

void TextDump()
{
  static int CGASizes[]  = {
    1, 3, 7, 3, 3   };
  static int NormSizes[] = {
    1, 4, 7, 4, 4   };

  char buffer[80];
  int font, ch, wwidth, lwidth, size;
  struct viewporttype vp;

  for( font=0 ; font<5 ; ++font ){    /* For each available font    */
    sprintf( buffer, "%s Character Set", Fonts[font] );
    MainWindow( buffer );        /* Display fontname as banner    */
    getviewsettings( &vp );        /* read current viewport    */

    settextjustify( LEFT_TEXT, TOP_TEXT );
    moveto( 2, 3 );

    buffer[1] = '\0';                   /* Terminate string             */
    wwidth = vp.right - vp.left;    /* Determine the window width    */
    lwidth = textwidth( "H" );          /* Get average letter width     */

    if( font == DEFAULT_FONT ){
      changetextstyle( font, HORIZ_DIR, 1 );
      ch = 0;
      while( ch < 256 ){        /* For each possible character    */
    buffer[0] = ch;         /* Put character into a string    */
    outtext( buffer );        /* send string to screen    */
    if( (getx() + lwidth) > wwidth )
      moveto( 2, gety() + textheight("H") + 3 );
    ++ch;                /* Goto the next character    */
      }
    }
    else{

      size = (MaxY < 200) ? CGASizes[font] : NormSizes[font];
      changetextstyle( font, HORIZ_DIR, size );

      ch = '!';                         /* Begin at 1st printable       */
      while( ch < 127 ){        /* For each printable character */
    buffer[0] = ch;         /* Put character into a string    */
    outtext( buffer );        /* send string to screen    */
    if( (lwidth+getx()) > wwidth )    /* Are we still in window?    */
      moveto( 2, gety()+textheight("H")+3 );
    ++ch;                /* Goto the next character    */
      }

    }

    Pause();                /* Pause until user acks    */

  }                    /* End of FONT loop        */

}

/*                                    */
/*    BAR3DDEMO: Display a 3-D bar chart on the screen.        */
/*                                    */

void Bar3DDemo(void)
{
  static int barheight[] = {
    1, 3, 5, 4, 3, 2, 1, 5, 4, 2, 3   };
  struct viewporttype vp;
  int xstep, ystep;
  int i, j, h, color, bheight;
  char buffer[10];

  MainWindow( "Bar 3-D / Rectangle Demonstration" );

  h = 3 * textheight( "H" );
  getviewsettings( &vp );
  settextjustify( CENTER_TEXT, TOP_TEXT );
  changetextstyle( TRIPLEX_FONT, HORIZ_DIR, 4 );
  outtextxy( MaxX/2, 6, "These are 3-D Bars" );
  changetextstyle( DEFAULT_FONT, HORIZ_DIR, 1 );
  setviewport( vp.left+50, vp.top+40, vp.right-50, vp.bottom-10, 1 );
  getviewsettings( &vp );

  line( h, h, h, vp.bottom-vp.top-h );
  line( h, (vp.bottom-vp.top)-h, (vp.right-vp.left)-h, (vp.bottom-vp.top)-h );
  xstep = ((vp.right-vp.left) - (2*h)) / 10;
  ystep = ((vp.bottom-vp.top) - (2*h)) / 5;
  j = (vp.bottom-vp.top) - h;
  settextjustify( CENTER_TEXT, CENTER_TEXT );

  for( i=0 ; i<6 ; ++i ){
    line( h/2, j, h, j );
    itoa( i, buffer, 10 );
    outtextxy( 0, j, buffer );
    j -= ystep;
  }

  j = h;
  settextjustify( CENTER_TEXT, TOP_TEXT );

  for( i=0 ; i<11 ; ++i ){
    color = random( MaxColors );
    setfillstyle( i+1, color );
    line( j, (vp.bottom-vp.top)-h, j, (vp.bottom-vp.top-3)-(h/2) );
    itoa( i, buffer, 10 );
    outtextxy( j, (vp.bottom-vp.top)-(h/2), buffer );
    if( i != 10 ){
      bheight = (vp.bottom-vp.top) - h - 1;
      bar3d( j, (vp.bottom-vp.top-h)-(barheight[i]*ystep), j+xstep, bheight, 15, 1 );
    }
    j += xstep;
  }

  Pause();                /* Pause for user's response    */

}

/*                                    */
/*    RANDOMBARS: Display random bars                 */
/*                                    */

void RandomBars(void)
{
  int color;

  MainWindow( "Random Bars" );
  StatusLine( "Esc aborts or press a key..." ); /* Put msg at bottom of screen   */
  while( !kbhit() ){            /* Until user enters a key...    */
    color = random( MaxColors-1 )+1;
    setcolor( color );
    setfillstyle( random(11)+1, color );
    bar3d( random( getmaxx() ), random( getmaxy() ),
       random( getmaxx() ), random( getmaxy() ), 0, OFF);
  }

  Pause();                /* Pause for user's response    */

}


/*                                    */
/*    TEXTDEMO: Show each font in several sizes to the user.        */
/*                                    */

void TextDemo(void)
{
  int charsize[] = {
    1, 3, 7, 3, 4   };
  int font, size;
  int h, x, y, i;
  struct viewporttype vp;
  char buffer[80];

  for( font=0 ; font<5 ; ++font ){    /* For each of the four fonts    */

    sprintf( buffer, "%s Demonstration", Fonts[font] );
    MainWindow( buffer );
    getviewsettings( &vp );

    changetextstyle( font, VERT_DIR, charsize[font] );
    settextjustify( CENTER_TEXT, BOTTOM_TEXT );
    outtextxy( 2*textwidth("M"), vp.bottom - 2*textheight("M"), "Vertical" );

    changetextstyle( font, HORIZ_DIR, charsize[font] );
    settextjustify( LEFT_TEXT, TOP_TEXT );
    outtextxy( 2*textwidth("M"), 2, "Horizontal" );

    settextjustify( CENTER_TEXT, CENTER_TEXT );
    x = (vp.right - vp.left) / 2;
    y = textheight( "H" );

    for( i=1 ; i<5 ; ++i ){        /* For each of the sizes */
      size = (font == SMALL_FONT) ? i+3 : i;
      changetextstyle( font, HORIZ_DIR, size );
      h = textheight( "H" );
      y += h;
      sprintf( buffer, "Size %d", size );
      outtextxy( x, y, buffer );

    }

    if( font != DEFAULT_FONT ){     /* Show user declared font size */
      y += h / 2;            /* Move down the screen     */
      settextjustify( CENTER_TEXT, TOP_TEXT );
      setusercharsize( 5, 6, 3, 2 );
      changetextstyle( font, HORIZ_DIR, USER_CHAR_SIZE );
      outtextxy( (vp.right-vp.left)/2, y, "User Defined Size" );
    }

    Pause();                /* Pause to let user look    */

  }                    /* End of FONT loop        */

}

/*                                    */
/*    COLORDEMO: Display the current color palette on the screen.    */
/*                                    */

void ColorDemo(void)
{
  struct viewporttype vp;
  int color, height, width;
  int x, y, i, j;
  char cnum[5];

  MainWindow( "Color Demonstration" );  /* Show demonstration name      */

  color = 1;
  getviewsettings( &vp );        /* Get the current window size    */
  width  = 2 * ( (vp.right+1) / 16 );       /* Get box dimensions       */
  height = 2 * ( (vp.bottom-10) / 10 );

  x = width / 2;
  y = height / 2;    /* Leave 1/2 box border     */

  for( j=0 ; j<3 ; ++j ){        /* Row loop            */

    for( i=0 ; i<5 ; ++i ){        /* Column loop            */

      setfillstyle(SOLID_FILL, color);    /* Set to solid fill in color    */
      setcolor( color );        /* Set the same border color    */

      bar( x, y, x+width, y+height );    /* Draw the rectangle        */
      rectangle( x, y, x+width, y+height );  /* outline the rectangle    */

      if( color == BLACK ){        /* If box was black...        */
    setcolor( WHITE );        /* Set drawing color to white    */
    rectangle( x, y, x+width, y+height );  /* Outline black in white*/
      }

      itoa( color, cnum, 10 );        /* Convert # to ASCII        */
      outtextxy( x+(width/2), y+height+4, cnum );  /* Show color #    */

      color = ++color % MaxColors;    /* Advance to the next color    */
      x += (width / 2) * 3;        /* move the column base     */
    }                /* End of Column loop        */

    y += (height / 2) * 3;        /* move the row base        */
    x = width / 2;            /* reset column base        */
  }                    /* End of Row loop        */

  Pause();                /* Pause for user's response    */

}

/*                                    */
/*    ARCDEMO: Display a random pattern of arcs on the screen */
/*    until the user says enough.                    */
/*                                    */

void ArcDemo(void)
{
  int mradius;                /* Maximum radius allowed    */
  int eangle;                /* Random end angle of Arc    */
  struct arccoordstype ai;        /* Used to read Arc Cord info    */

  MainWindow( "Arc Demonstration" );
  StatusLine( "ESC Aborts - Press a Key to stop" );

  mradius = MaxY / 10;            /* Determine the maximum radius */

  while( !kbhit() ){            /* Repeat until a key is hit    */
    setcolor( random( MaxColors - 1 ) + 1 );    /* Randomly select a color    */
    eangle = random( 358 ) + 1;     /* Select an end angle        */
    arc( random(MaxX), random(MaxY), random(eangle), eangle, mradius );
    getarccoords( &ai );        /* Read Cord data        */
    line( ai.x, ai.y, ai.xstart, ai.ystart ); /* line from start to center */
    line( ai.x, ai.y,    ai.xend,   ai.yend ); /* line from end to center   */
  }                    /* End of WHILE not KBHIT    */

  Pause();                /* Wait for user's response     */

}

/*                                    */
/*    CIRCLEDEMO: Display a random pattern of circles on the screen    */
/*    until the user says enough.                    */
/*                                    */

void CircleDemo(void)
{
  int mradius;                /* Maximum radius allowed    */

  MainWindow( "Circle Demonstration" );
  StatusLine( "ESC Aborts - Press a Key to stop" );

  mradius = MaxY / 10;            /* Determine the maximum radius */

  while( !kbhit() ){            /* Repeat until a key is hit    */
    setcolor( random( MaxColors - 1 ) + 1 );    /* Randomly select a color    */
    circle( random(MaxX), random(MaxY), random(mradius) );
  }                    /* End of WHILE not KBHIT    */

  Pause();                /* Wait for user's response     */

}

/*                                    */
/*    PIEDEMO: Display a pie chart on the screen.            */
/*                                    */

#define adjasp( y )    ((int)(AspectRatio * (double)(y)))
#define torad( d )    (( (double)(d) * PI ) / 180.0 )

void PieDemo(void)
{
  struct viewporttype vp;
  int xcenter, ycenter, radius, lradius;
  int x, y;
  double radians, piesize;

  MainWindow( "Pie Chart Demonstration" );

  getviewsettings( &vp );        /* Get the current viewport    */
  xcenter = (vp.right - vp.left) / 2;    /* Center the Pie horizontally    */
  ycenter = (vp.bottom - vp.top) / 2+20;/* Center the Pie vertically    */
  radius  = (vp.bottom - vp.top) / 3;    /* It will cover 2/3rds screen    */
  piesize = (vp.bottom - vp.top) / 4.0; /* Optimum height ratio of pie    */

  while( (AspectRatio*radius) < piesize ) ++radius;

  lradius = radius + ( radius / 5 );    /* Labels placed 20% farther    */

  changetextstyle( TRIPLEX_FONT, HORIZ_DIR, 4 );
  settextjustify( CENTER_TEXT, TOP_TEXT );
  outtextxy( MaxX/2, 6, "This is a Pie Chart" );
  changetextstyle( TRIPLEX_FONT, HORIZ_DIR, 1 );
  settextjustify( CENTER_TEXT, TOP_TEXT );

  setfillstyle( SOLID_FILL, RED );
  pieslice( xcenter+10, ycenter-adjasp(10), 0, 90, radius );
  radians = torad( 45 );
  x = xcenter + (int)( cos( radians ) * (double)lradius );
  y = ycenter - (int)( sin( radians ) * (double)lradius * AspectRatio );
  settextjustify( LEFT_TEXT, BOTTOM_TEXT );
  outtextxy( x, y, "25 %" );

  setfillstyle( WIDE_DOT_FILL, GREEN );
  pieslice( xcenter, ycenter, 90, 135, radius );
  radians = torad( 113 );
  x = xcenter + (int)( cos( radians ) * (double)lradius );
  y = ycenter - (int)( sin( radians ) * (double)lradius * AspectRatio );
  settextjustify( RIGHT_TEXT, BOTTOM_TEXT );
  outtextxy( x, y, "12.5 %" );

  setfillstyle( INTERLEAVE_FILL, YELLOW );
  settextjustify( RIGHT_TEXT, CENTER_TEXT );
  pieslice( xcenter-10, ycenter, 135, 225, radius );
  radians = torad( 180 );
  x = xcenter + (int)( cos( radians ) * (double)lradius );
  y = ycenter - (int)( sin( radians ) * (double)lradius * AspectRatio );
  settextjustify( RIGHT_TEXT, CENTER_TEXT );
  outtextxy( x, y, "25 %" );

  setfillstyle( HATCH_FILL, BLUE );
  pieslice( xcenter, ycenter, 225, 360, radius );
  radians = torad( 293 );
  x = xcenter + (int)( cos( radians ) * (double)lradius );
  y = ycenter - (int)( sin( radians ) * (double)lradius * AspectRatio );
  settextjustify( LEFT_TEXT, TOP_TEXT );
  outtextxy( x, y, "37.5 %" );

  Pause();                /* Pause for user's response    */

}

/*                                    */
/*    BARDEMO: Draw a 2-D bar chart using Bar and Rectangle.        */
/*                                    */

void BarDemo(void)
{
  int barheight[] = {
    1, 3, 5, 2, 4   };
  int styles[]      = {
    1, 3, 10, 5, 9, 1    };
  int xstep, ystep;
  int sheight, swidth;
  int i, j, h;
  struct viewporttype vp;
  char buffer[40];

  MainWindow( "Bar / Rectangle demonstration" );
  h = 3 * textheight( "H" );
  getviewsettings( &vp );
  settextjustify( CENTER_TEXT, TOP_TEXT );
  changetextstyle( TRIPLEX_FONT, HORIZ_DIR, 4 );
  outtextxy( MaxX /2, 6, "These are 2-D Bars" );
  changetextstyle( DEFAULT_FONT, HORIZ_DIR, 1 );
  setviewport( vp.left+50, vp.top+30, vp.right-50, vp.bottom-10, 1 );

  getviewsettings( &vp );
  sheight = vp.bottom - vp.top;
  swidth  = vp.right  - vp.left;

  line( h, h, h, sheight-h );
  line( h, sheight-h, sheight-h, sheight-h );
  ystep = (sheight - (2*h) ) / 5;
  xstep = (swidth  - (2*h) ) / 5;
  j = sheight - h;
  settextjustify( CENTER_TEXT, CENTER_TEXT );

  for( i=0 ; i<6 ; ++i ){
    line( h/2, j, h, j );
    itoa( i, buffer, 10 );
    outtextxy( 0, j, buffer );
    j -= ystep;
  }

  j = h;
  settextjustify( CENTER_TEXT, TOP_TEXT );
  for( i=0 ; i<6 ; ++i ){
    setfillstyle( styles[i], random(MaxColors) );
    line( j, sheight - h, j, sheight- 3 - (h/2) );
    itoa( i, buffer, 10 );
    outtextxy( j, sheight - (h/2), buffer );
    if( i != 5 ){
      bar( j, (sheight-h)-(barheight[i] * ystep), j+xstep, sheight-h-1 );
      rectangle( j, (sheight-h)-(barheight[i] * ystep), j+xstep, sheight-h);
    }
    j += xstep;
  }

  Pause();

}

/*                                    */
/*    LINERELDEMO: Display pattern using moverel and linerel cmds.    */
/*                                    */

void LineRelDemo(void)
{
  struct viewporttype vp;
  int h, w, dx, dy, cx, cy;
  struct PTS outs[7];


  MainWindow( "MoveRel / LineRel Demonstration" );
  StatusLine( "Press any key to continue, ESC to Abort" );

  getviewsettings( &vp );
  cx = (vp.right  - vp.left) / 2;    /* Center of the screen coords    */
  cy = (vp.bottom - vp.top ) / 2;

  h  = (vp.bottom - vp.top ) / 8;
  w  = (vp.right  - vp.left) / 9;

  dx = 2 * w;
  dy = 2 * h;

  setcolor( BLACK );

  setfillstyle( SOLID_FILL, BLUE );
  bar( 0, 0, vp.right-vp.left, vp.bottom-vp.top );    /* Draw backgnd */

  outs[0].x = cx -  dx;
  outs[0].y = cy -  dy;
  outs[1].x = cx - (dx-w);
  outs[1].y = cy - (dy+h);
  outs[2].x = cx +  dx;
  outs[2].y = cy - (dy+h);
  outs[3].x = cx +  dx;
  outs[3].y = cy +  dy;
  outs[4].x = cx + (dx-w);
  outs[4].y = cy + (dy+h);
  outs[5].x = cx -  dx;
  outs[5].y = cy + (dy+h);
  outs[6].x = cx -  dx;
  outs[6].y = cy -  dy;

  setfillstyle( SOLID_FILL, WHITE );
  fillpoly( 7, (int far *)outs );

  outs[0].x = cx - (w/2);
  outs[0].y = cy + h;
  outs[1].x = cx + (w/2);
  outs[1].y = cy + h;
  outs[2].x = cx + (w/2);
  outs[2].y = cy - h;
  outs[3].x = cx - (w/2);
  outs[3].y = cy - h;
  outs[4].x = cx - (w/2);
  outs[4].y = cy + h;

  setfillstyle( SOLID_FILL, BLUE );
  fillpoly( 5, (int far *)outs );

  /*    Draw a Tesseract object on the screen using the LineRel and    */
  /*    MoveRel drawing commands.                    */

  moveto( cx-dx, cy-dy );
  linerel(  w, -h );
  linerel(  3*w,    0 );
  linerel(   0,  5*h );
  linerel( -w,    h );
  linerel( -3*w,    0 );
  linerel(   0, -5*h );

  moverel( w, -h );
  linerel(   0,  5*h );
  linerel( w+(w/2), 0 );
  linerel(   0, -3*h );
  linerel( w/2,   -h );
  linerel( 0, 5*h );

  moverel(  0, -5*h );
  linerel( -(w+(w/2)), 0 );
  linerel( 0, 3*h );
  linerel( -w/2, h );

  moverel( w/2, -h );
  linerel( w, 0 );

  moverel( 0, -2*h );
  linerel( -w, 0 );

  Pause();                /* Wait for user's response     */

}

/*                                    */
/*    PUTPIXELDEMO: Display a pattern of random dots on the screen    */
/*    and pick them back up again.                    */
/*                                    */

void PutPixelDemo(void)
{
  int seed = 1958;
  int i, x, y, h, w, color;
  struct viewporttype vp;

  MainWindow( "PutPixel / GetPixel Demonstration" );

  getviewsettings( &vp );
  h = vp.bottom - vp.top;
  w = vp.right    - vp.left;

  srand( seed );            /* Restart random # function    */

  for( i=0 ; i<5000 ; ++i ){        /* Put 5000 pixels on screen    */
    x = 1 + random( w - 1 );        /* Generate a random location    */
    y = 1 + random( h - 1 );
    color = random( MaxColors );
    putpixel( x, y, color );
  }

  srand( seed );            /* Restart Random # at same #    */

  for( i=0 ; i<5000 ; ++i ){        /* Take the 5000 pixels off    */
    x = 1 + random( w - 1 );        /* Generate a random location    */
    y = 1 + random( h - 1 );
    color = getpixel( x, y );        /* Read the color pixel     */
    if( color == random( MaxColors ) )    /* Used to keep RANDOM in sync    */
      putpixel( x, y, 0 );        /* Write pixel to BLACK     */
  }

  Pause();                /* Wait for user's response     */

}

/*                                    */
/*   PUTIMAGEDEMO                            */
/*                                    */
void PutImageDemo(void)
{
  static int r        = 20;
  static int StartX = 100;
  static int StartY = 50;

  struct viewporttype vp;
  int PauseTime, x, y, ulx, uly, lrx, lry, size, i, width, height, step;
  void *Saucer;

  MainWindow("GetImage / PutImage Demonstration");
  getviewsettings( &vp );

  /* Draw Saucer */
  setfillstyle( SOLID_FILL, getmaxcolor() );
  fillellipse(StartX, StartY, r, (r/3)+2);
  ellipse(StartX, StartY-4, 190, 357, r, r/3);

  line(StartX+7, StartY-6, StartX+10, StartY-12);
  circle(StartX+10, StartY-12, 2);
  line(StartX-7, StartY-6, StartX-10, StartY-12);
  circle(StartX-10, StartY-12, 2);


  /* Read saucer image */
  ulx = StartX-(r+1);
  uly = StartY-14;
  lrx = StartX+(r+1);
  lry = StartY+(r/3)+3;
  width = lrx - ulx + 1;
  height = lry - uly + 1;
  size = imagesize(ulx, uly, lrx, lry);

  Saucer = malloc( size );
  getimage(ulx, uly, lrx, lry, Saucer);
  putimage(ulx, uly, Saucer, XOR_PUT);

/* Plot some "stars"  */
  for ( i=0 ; i<1000; ++i )
    putpixel(random(MaxX), random(MaxY), random( MaxColors-1 )+1);
  x = MaxX / 2;
  y = MaxY / 2;
  PauseTime = 70;

  /* until a key is hit */
  while ( !kbhit() ) {

    /* Draw the Saucer */
    putimage(x, y, Saucer, XOR_PUT);             /*  draw image  */
    delay(PauseTime);
    putimage(x, y, Saucer, XOR_PUT);             /* erase image  */

    /* Move Saucer */

    step = random( 2*r );
    if ((step/2) % 2 != 0 )
      step = -1 * step;
    x = x + step;
    step = random( r );
    if ((step/2) % 2 != 0 )
      step = -1 * step;
    y = y + step;

    if (vp.left + x + width - 1 > vp.right)
      x = vp.right-vp.left-width + 1;
    else
      if (x < 0)
    x = 0;
    if (vp.top + y + height - 1 > vp.bottom)
      y = vp.bottom-vp.top-height + 1;
    else
      if (y < 0)
    y = 0;
  }
  free( Saucer );
  Pause();
}


/*                                    */
/*    LINETODEMO: Display a pattern using moveto and lineto commands. */
/*                                    */

#define MAXPTS    15

void LineToDemo(void)
{
  struct viewporttype vp;
  struct PTS points[MAXPTS];
  int i, j, h, w, xcenter, ycenter;
  int radius, angle, step;
  double  rads;

  MainWindow( "MoveTo / LineTo Demonstration" );

  getviewsettings( &vp );
  h = vp.bottom - vp.top;
  w = vp.right    - vp.left;

  xcenter = w / 2;            /* Determine the center of circle */
  ycenter = h / 2;
  radius  = (h - 30) / (AspectRatio * 2);
  step      = 360 / MAXPTS;        /* Determine # of increments    */

  angle = 0;                /* Begin at zero degrees    */
  for( i=0 ; i<MAXPTS ; ++i ){        /* Determine circle intercepts    */
    rads = (double)angle * PI / 180.0;    /* Convert angle to radians    */
    points[i].x = xcenter + (int)( cos(rads) * radius );
    points[i].y = ycenter - (int)( sin(rads) * radius * AspectRatio );
    angle += step;            /* Move to next increment    */
  }

  circle( xcenter, ycenter, radius );    /* Draw bounding circle     */

  for( i=0 ; i<MAXPTS ; ++i ){        /* Draw the cords to the circle */
    for( j=i ; j<MAXPTS ; ++j ){    /* For each remaining intersect */
      moveto(points[i].x, points[i].y); /* Move to beginning of cord    */
      lineto(points[j].x, points[j].y); /* Draw the cord        */
    }
  }

  Pause();                /* Wait for user's response     */

}

/*                                    */
/*    LINESTYLEDEMO: Display a pattern using all of the standard    */
/*    line styles that are available.                 */
/*                                    */

void LineStyleDemo(void)
{
  int style, step;
  int x, y, w;
  struct viewporttype vp;
  char buffer[40];

  MainWindow( "Pre-defined line styles" );

  getviewsettings( &vp );
  w = vp.right    - vp.left;

  x = 35;
  y = 10;
  step = w / 11;

  settextjustify( LEFT_TEXT, TOP_TEXT );
  outtextxy( x, y, "Normal Width" );

  settextjustify( CENTER_TEXT, TOP_TEXT );

  for( style=0 ; style<4 ; ++style ){
    setlinestyle( style, 0, NORM_WIDTH );
    line( x, y+20, x, vp.bottom-40 );
    itoa( style, buffer, 10 );
    outtextxy( x, vp.bottom-30, buffer );
    x += step;
  }

  x += 2 * step;

  settextjustify( LEFT_TEXT, TOP_TEXT );
  outtextxy( x, y, "Thick Width" );
  settextjustify( CENTER_TEXT, TOP_TEXT );

  for( style=0 ; style<4 ; ++style ){
    setlinestyle( style, 0, THICK_WIDTH );
    line( x, y+20, x, vp.bottom-40 );
    itoa( style, buffer, 10 );
    outtextxy( x, vp.bottom-30, buffer );
    x += step;
  }

  settextjustify( LEFT_TEXT, TOP_TEXT );

  Pause();                /* Wait for user's response     */

}

/*                                    */
/*    CRTMODEDEMO: Demonstrate the effects of the change mode     */
/*    commands on the current screen.                 */
/*                                    */

void CRTModeDemo(void)
{
  struct viewporttype vp;
  int mode;

  MainWindow( "SetGraphMode / RestoreCRTMode demo" );
  getviewsettings( &vp );
  mode = getgraphmode();
  settextjustify( CENTER_TEXT, CENTER_TEXT );

  outtextxy( (vp.right-vp.left)/2, (vp.bottom-vp.top)/2,
  "Now you are in graphics mode..." );
  StatusLine( "Press any key for text mode..." );
  getch();

  restorecrtmode();
  printf( "Now you are in text mode.\n\n" );
  printf( "Press any key to go back to graphics..." );
  getch();

  setgraphmode( mode );
  MainWindow( "SetGraphMode / RestoreCRTMode demo" );
  settextjustify( CENTER_TEXT, CENTER_TEXT );
  outtextxy( (vp.right-vp.left)/2, (vp.bottom-vp.top)/2,
  "Back in Graphics Mode..." );

  Pause();                /* Wait for user's response     */

}

/*                                    */
/*    USERLINESTYLEDEMO: Display line styles showing the user     */
/*    defined line style functions.                    */
/*                                    */

void UserLineStyleDemo(void)
{
  int x, y, i, h, flag;
  unsigned int style;
  struct viewporttype vp;

  MainWindow( "User defined line styles" );

  getviewsettings( &vp );
  h = vp.bottom - vp.top;

  x = 4;
  y = 10;
  style = 0;
  i = 0;

  settextjustify( CENTER_TEXT, TOP_TEXT );
  flag = TRUE;                /* Set the bits in this pass    */

  while( x < vp.right-2 ){        /* Draw lines across the screen */

    if( flag )                /* If flag, set bits...     */
      style = style | (1 << i);     /*    Set the Ith bit in word    */
    else                /* If no flag, clear bits    */
    style = style & !(0x8000 >> i);    /*    Clear the Ith bit in word */

    setlinestyle( USERBIT_LINE, style, NORM_WIDTH );
    line( x, y, x, h-y );        /* Draw the new line pattern    */

    x += 5;                /* Move the X location of line    */
    i = ++i % 16;            /* Advance to next bit pattern    */

    if( style == 0xffff ){        /* Are all bits set?        */
      flag = FALSE;            /*   begin removing bits    */
      i = 0;                /* Start with whole pattern    */
    }
    else{                /* Bits not all set...        */
      if( style == 0 )            /* Are all bits clear?        */
    flag = TRUE;            /*   begin setting bits     */
    }
  }

  settextjustify( LEFT_TEXT, TOP_TEXT );

  Pause();                /* Wait for user's response     */

}

/*                                    */
/*    FILLSTYLEDEMO: Display the standard fill patterns available.    */
/*                                    */

void FillStyleDemo(void)
{
  int h, w, style;
  int i, j, x, y;
  struct viewporttype vp;
  char buffer[40];

  MainWindow( "Pre-defined Fill Styles" );

  getviewsettings( &vp );
  w = 2 * ((vp.right  +  1) / 13);
  h = 2 * ((vp.bottom - 10) / 10);

  x = w / 2;
  y = h / 2;        /* Leave 1/2 blk margin     */
  style = 0;

  for( j=0 ; j<3 ; ++j ){        /* Three rows of boxes        */
    for( i=0 ; i<4 ; ++i ){        /* Four column of boxes     */
      setfillstyle(style, MaxColors-1); /* Set the fill style and WHITE */
      bar( x, y, x+w, y+h );        /* Draw the actual box        */
      rectangle( x, y, x+w, y+h );    /* Outline the box        */
      itoa( style, buffer, 10 );    /* Convert style 3 to ASCII    */
      outtextxy( x+(w / 2), y+h+4, buffer );
      ++style;                /* Go on to next style #    */
      x += (w / 2) * 3;         /* Go to next column        */
    }                /* End of coulmn loop        */
    x = w / 2;                /* Put base back to 1st column    */
    y += (h / 2) * 3;            /* Advance to next row        */
  }                    /* End of Row loop        */

  settextjustify( LEFT_TEXT, TOP_TEXT );

  Pause();                /* Wait for user's response     */

}

/*                                    */
/*    FILLPATTERNDEMO: Demonstrate how to use the user definable    */
/*    fill patterns.                            */
/*                                    */

void FillPatternDemo(void)
{
  int style;
  int h, w;
  int x, y, i, j;
  char buffer[40];
  struct viewporttype vp;
  static char patterns[][8] = {
    { 0xAA, 0x55, 0xAA, 0x55, 0xAA, 0x55, 0xAA, 0x55 },
    { 0x33, 0x33, 0xCC, 0xCC, 0x33, 0x33, 0xCC, 0xCC },
    { 0xF0, 0xF0, 0xF0, 0xF0, 0x0F, 0x0F, 0x0F, 0x0F },
    { 0x00, 0x10, 0x28, 0x44, 0x28, 0x10, 0x00, 0x00 },
    { 0x00, 0x70, 0x20, 0x27, 0x24, 0x24, 0x07, 0x00 },
    { 0x00, 0x00, 0x00, 0x18, 0x18, 0x00, 0x00, 0x00 },
    { 0x00, 0x00, 0x3C, 0x3C, 0x3C, 0x3C, 0x00, 0x00 },
    { 0x00, 0x7E, 0x7E, 0x7E, 0x7E, 0x7E, 0x7E, 0x00 },
    { 0x00, 0x00, 0x22, 0x08, 0x00, 0x22, 0x1C, 0x00 },
    { 0xFF, 0x7E, 0x3C, 0x18, 0x18, 0x3C, 0x7E, 0xFF },
    { 0x00, 0x10, 0x10, 0x7C, 0x10, 0x10, 0x00, 0x00 },
    { 0x00, 0x42, 0x24, 0x18, 0x18, 0x24, 0x42, 0x00 }
  };

  MainWindow( "User Defined Fill Styles" );

  getviewsettings( &vp );
  w = 2 * ((vp.right  +  1) / 13);
  h = 2 * ((vp.bottom - 10) / 10);

  x = w / 2;
  y = h / 2;        /* Leave 1/2 blk margin     */
  style = 0;

  for( j=0 ; j<3 ; ++j ){        /* Three rows of boxes        */
    for( i=0 ; i<4 ; ++i ){        /* Four column of boxes     */
      setfillpattern( &patterns[style][0], MaxColors-1 );
      bar( x, y, x+w, y+h );        /* Draw the actual box        */
      rectangle( x, y, x+w, y+h );    /* Outline the box        */
      itoa( style, buffer, 10 );    /* Convert style 3 to ASCII    */
      outtextxy( x+(w / 2), y+h+4, buffer );
      ++style;                /* Go on to next style #    */
      x += (w / 2) * 3;         /* Go to next column        */
    }                /* End of coulmn loop        */
    x = w / 2;                /* Put base back to 1st column    */
    y += (h / 2) * 3;            /* Advance to next row        */
  }                    /* End of Row loop        */

  settextjustify( LEFT_TEXT, TOP_TEXT );

  Pause();                /* Wait for user's response     */

}

/*                                    */
/*    POLYDEMO: Display a random pattern of polygons on the screen    */
/*    until the user says enough.                    */
/*                                    */

void PaletteDemo(void)
{
  int i, j, x, y, color;
  struct viewporttype vp;
  int height, width;

  MainWindow( "Palette Demonstration" );
  StatusLine( "Press any key to continue, ESC to Abort" );

  getviewsettings( &vp );
  width  = (vp.right - vp.left) / 15;    /* get width of the box     */
  height = (vp.bottom - vp.top) / 10;    /* Get the height of the box    */

  x = y = 0;                /* Start in upper corner    */
  color = 1;                /* Begin at 1st color        */

  for( j=0 ; j<10 ; ++j ){        /* For 10 rows of boxes     */
    for( i=0 ; i<15 ; ++i ){        /* For 15 columns of boxes    */
      setfillstyle( SOLID_FILL, color++ );    /* Set the color of box */
      bar( x, y, x+width, y+height );        /* Draw the box     */
      x += width + 1;                /* Advance to next col    */
      color = 1 + (color % (MaxColors - 2));    /* Set new color    */
    }                /* End of COLUMN loop        */
    x = 0;                /* Goto 1st column        */
    y += height + 1;            /* Goto next row        */
  }                    /* End of ROW loop        */

  while( !kbhit() ){            /* Until user enters a key...    */
    setpalette( 1+random(MaxColors - 2), random( 65 ) );
  }

  setallpalette( &palette );

  Pause();                /* Wait for user's response     */

}

/*                                    */
/*    POLYDEMO: Display a random pattern of polygons on the screen    */
/*    until the user says enough.                    */
/*                                    */

#define MaxPts        6        /* Maximum # of pts in polygon    */

void PolyDemo(void)
{
  struct PTS poly[ MaxPts ];        /* Space to hold datapoints    */
  int color;                /* Current drawing color    */
  int i;

  MainWindow( "DrawPoly / FillPoly Demonstration" );
  StatusLine( "ESC Aborts - Press a Key to stop" );

  while( !kbhit() ){            /* Repeat until a key is hit    */

    color = 1 + random( MaxColors-1 );    /* Get a random color # (no blk)*/
    setfillstyle( random(10), color );    /* Set a random line style    */
    setcolor( color );            /* Set the desired color    */

    for( i=0 ; i<(MaxPts-1) ; i++ ){    /* Determine a random polygon    */
      poly[i].x = random( MaxX );    /* Set the x coord of point    */
      poly[i].y = random( MaxY );    /* Set the y coord of point    */
    }

    poly[i].x = poly[0].x;        /* last point = first point    */
    poly[i].y = poly[1].y;

    fillpoly( MaxPts, (int far *)poly );    /* Draw the actual polygon        */
  }                    /* End of WHILE not KBHIT    */

  Pause();                /* Wait for user's response     */

}


/*                                    */
/*    SAYGOODBYE: Give a closing screen to the user before leaving.    */
/*                                    */

void SayGoodbye(void)
{
  struct viewporttype viewinfo;     /* Structure to read viewport    */
  int h, w;

  MainWindow( "== Finale ==" );

  getviewsettings( &viewinfo );     /* Read viewport settings    */
  changetextstyle( TRIPLEX_FONT, HORIZ_DIR, 4 );
  settextjustify( CENTER_TEXT, CENTER_TEXT );

  h = viewinfo.bottom - viewinfo.top;
  w = viewinfo.right  - viewinfo.left;
  outtextxy( w/2, h/2, "That's all, folks!" );

  StatusLine( "Press any key to EXIT" );
  getch();

  cleardevice();            /* Clear the graphics screen    */

}

/*                                    */
/*    PAUSE: Pause until the user enters a keystroke. If the        */
/*    key is an ESC, then exit program, else simply return.        */
/*                                    */

void Pause(void)
{
  static char msg[] = "Esc aborts or press a key...";
  int c;

  StatusLine( msg );            /* Put msg at bottom of screen    */

  c = getch();                /* Read a character from kbd    */

  if( ESC == c ){            /* Does user wish to leave?    */
    closegraph();            /* Change to text mode        */
    exit( 1 );                /* Return to OS         */
  }

  if( 0 == c ){             /* Did use hit a non-ASCII key? */
    c = getch();            /* Read scan code for keyboard    */
  }

  cleardevice();            /* Clear the screen        */

}

/*                                    */
/*    MAINWINDOW: Establish the main window for the demo and set    */
/*    a viewport for the demo code.                    */
/*                                    */

void MainWindow( char *header )
{
  int height;

  cleardevice();            /* Clear graphics screen    */
  setcolor( MaxColors - 1 );        /* Set current color to white    */
  setviewport( 0, 0, MaxX, MaxY, 1 );    /* Open port to full screen    */

  height = textheight( "H" );           /* Get basic text height        */

  changetextstyle( DEFAULT_FONT, HORIZ_DIR, 1 );
  settextjustify( CENTER_TEXT, TOP_TEXT );
  outtextxy( MaxX/2, 2, header );
  setviewport( 0, height+4, MaxX, MaxY-(height+4), 1 );
  DrawBorder();
  setviewport( 1, height+5, MaxX-1, MaxY-(height+5), 1 );

}

/*                                    */
/*    STATUSLINE: Display a status line at the bottom of the screen.    */
/*                                    */

void StatusLine( char *msg )
{
  int height;

  setviewport( 0, 0, MaxX, MaxY, 1 );    /* Open port to full screen    */
  setcolor( MaxColors - 1 );        /* Set current color to white    */

  changetextstyle( DEFAULT_FONT, HORIZ_DIR, 1 );
  settextjustify( CENTER_TEXT, TOP_TEXT );
  setlinestyle( SOLID_LINE, 0, NORM_WIDTH );
  setfillstyle( EMPTY_FILL, 0 );

  height = textheight( "H" );           /* Detemine current height      */
  bar( 0, MaxY-(height+4), MaxX, MaxY );
  rectangle( 0, MaxY-(height+4), MaxX, MaxY );
  outtextxy( MaxX/2, MaxY-(height+2), msg );
  setviewport( 1, height+5, MaxX-1, MaxY-(height+5), 1 );

}

/*                                    */
/*    DRAWBORDER: Draw a solid single line around the current     */
/*    viewport.                            */
/*                                    */

void DrawBorder(void)
{
  struct viewporttype vp;

  setcolor( MaxColors - 1 );        /* Set current color to white    */

  setlinestyle( SOLID_LINE, 0, NORM_WIDTH );

  getviewsettings( &vp );
  rectangle( 0, 0, vp.right-vp.left, vp.bottom-vp.top );

}

/*                                    */
/*    CHANGETEXTSTYLE: similar to settextstyle, but checks for    */
/*    errors that might occur whil loading the font file.        */
/*                                    */

void changetextstyle(int font, int direction, int charsize)
{
  int ErrorCode;

  graphresult();            /* clear error code        */
  settextstyle(font, direction, charsize);
  ErrorCode = graphresult();        /* check result         */
  if( ErrorCode != grOk ){        /* if error occured        */
    closegraph();
    printf(" Graphics System Error: %s\n", grapherrormsg( ErrorCode ) );
    exit( 1 );
  }
}

/*                                    */
/*    GPRINTF: Used like PRINTF except the output is sent to the    */
/*    screen in graphics mode at the specified co-ordinate.        */
/*                                    */

int gprintf( int *xloc, int *yloc, char *fmt, ... )
{
  va_list  argptr;            /* Argument list pointer    */
  char str[140];            /* Buffer to build sting into    */
  int cnt;                /* Result of SPRINTF for return */

  va_start( argptr, format );        /* Initialize va_ functions    */

  cnt = vsprintf( str, fmt, argptr );    /* prints string to buffer    */
  outtextxy( *xloc, *yloc, str );    /* Send string in graphics mode */
  *yloc += textheight( "H" ) + 2;       /* Advance to next line         */

  va_end( argptr );            /* Close va_ functions        */

  return( cnt );            /* Return the conversion count    */

}