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The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

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     There are three coordinate systems employed by the low-level
     graphics functions. The first is the physical screen coordinate
     system, where the origin (0,0) is located at the upper left corner
     of the screen and the coordinates increase downward and to the
     right. All coordinates must be integral values. Only setcliprgn,
     setviewport, setvieworg, getviewcoord, and getphyscoord require
     physical coordinates.
 
     The second is the viewport (or view) coordinate system. The
     graphics viewport is a clipping region with a coordinate system
     origin at its upper left corner. The default viewport is the
     physical screen, until a new one is defined using setviewport. The
     viewport origin can also be reset with setvieworg. All coordinates
     must be integral values. Functions without a suffix use view
     coordinates, and take shorts for coordinate arguments.
 
     The third is the window coordinate system. The setwindow function
     transforms the current graphics viewport into a window by mapping a
     real-valued coordinate system onto the viewport. Each coordinate
     can have an arbitrary range specified by the setwindow arguments.
     The y coordinate can be either increasing downward or increasing
     upward. Functions ending with _w use window coordinates, and take
     doubles for coordinate arguments.
 
     For translating between the various coordinate systems, use the
     getphyscoord, getviewcoord, and getwindowcoord functions.
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