Dots != Pixels

...atleast in the case of printers when accessed via GDI+ in .NET. For example, when a printer reports a DpiX of 600 and you say:

g->DrawLine(Pens::Black, 0.0f, 50.0f, 600.0f, 50.0f);

...the line drawn goes about three-fourths of the way across an A4 page. Some smart guy somewhere decided that it would be great to use a 1/100 inch co-ordinate system for printers so that the drawing routines used for video output would produce more or less the same size on the printer as well.