int Draw_Line(int x0, int y0, // starting position               int x1, int y1, // ending position              UCHAR color,    // color index              UCHAR *vb_start, int lpitch) // video buffer and memory pitch{// this function draws a line from xo,yo to x1,y1 using differential error// terms (based on Bresenahams work)int dx,             // difference in x''s    dy,             // difference in y''s    dx2,            // dx,dy * 2    dy2,     x_inc,          // amount in pixel space to move during drawing    y_inc,          // amount in pixel space to move during drawing    error,          // the discriminant i.e. error i.e. decision variable    index;          // used for looping// pre-compute first pixel address in video buffervb_start = vb_start + x0 + y0*lpitch;// compute horizontal and vertical deltasdx = x1-x0;dy = y1-y0;// test which direction the line is going in i.e. slope angleif (dx>=0)   {   x_inc = 1;   } // end if line is moving rightelse   {   x_inc = -1;   dx    = -dx;  // need absolute value   } // end else moving left// test y component of slopeif (dy>=0)   {   y_inc = lpitch;   } // end if line is moving downelse   {   y_inc = -lpitch;   dy    = -dy;  // need absolute value   } // end else moving up// compute (dx,dy) * 2dx2 = dx << 1;dy2 = dy << 1;// now based on which delta is greater we can draw the lineif (dx > dy)   {   // initialize error term   error = dy2 - dx;    // draw the line   for (index=0; index <= dx; index++)       {       // set the pixel       *vb_start = color;       // test if error has overflowed       if (error >= 0)           {          error-=dx2;          // move to next line          vb_start+=y_inc;	   } // end if error overflowed       // adjust the error term       error+=dy2;       // move to the next pixel       vb_start+=x_inc;       } // end for   } // end if |slope| <= 1else   {   // initialize error term   error = dx2 - dy;    // draw the line   for (index=0; index <= dy; index++)       {       // set the pixel       *vb_start = color;       // test if error overflowed       if (error >= 0)          {          error-=dy2;          // move to next line          vb_start+=x_inc;          } // end if error overflowed       // adjust the error term       error+=dx2;       // move to the next pixel       vb_start+=y_inc;       } // end for   } // end else |slope| > 1// return successreturn(1);} // end Draw_Line