12.3. Square Example   

We shall look at a typical (small) application using these routines (plus one other) to draw a SQUARE. Most of our algorithms will be in pseudo-code which should be easily translated into FORTRAN/Pascal/C.

Example draw a square of side 8" centred on screen. Screen is 22" by 16.75"

and starts at X=1.5 and Y origin = 1.0. All plots are relative to origin.

     program SQUARE


       call       export(stdin,stdout);       {Allow library to use stdio.}

       call       askdev(device);            {Which device to use?}

       call       start(2);              {initialize device}


       call       plot(9.5,7.375,-3);

       {Move, with origin reset : 9.5+1.5 = 11 = new X

                               7.375+1 = 8.375 = New Y

          therefore CENTRE       22/2 16.75/2  }

       call       plot(4.0,4.0,3);        {move to one corner}

       call       plot(4.0,-4.0,2);       {draw} {(1)}

       call       plot(-4.0,-4.0,2);             {(2)}

       call       plot(-4.0,4.0,2);

       call       plot(4.0,4.0,2);        {all sides }


       call       enplot;                {terminate devices}


    end_program_square.