Listing 1 


/*
   plot() = plots a point on the screen at designated    
            system coordinates using selected color.     
                                                         
*/



void plot(int x, int y, int color)      
{

    #define seq_out(index,val)  {outp(0x3C4,index);\
                     outp(0x3C5,val);}
    #define graph_out(index,val)  {outp(0x3CE,index);\
                     outp(0x3CF,val);}

    unsigned int offset;
    int dummy,mask,page;
    char far * mem_address;

    offset = (long)y * 80L + ((long)x / 8L);
    mem_address = (char far *) 0xA0000000L + offset;
    mask = 0x80 >> (x % 8);
    graph_out(8,mask);
    seq_out(2,0x0F);
    dummy = *mem_address;
    *mem_address = 0;
    seq_out(2,color);
    *mem_address = 0xFF;
    seq_out(2,0x0F);
    graph_out(3,0);
    graph_out(8,0xFF);

}