thecoalman - 2:05 am on Jan 11, 2013 (gmt 0)

Come to think of it, I have no idea what my monitor's physical resolution is.

I think you need to separate resolution and DPI, I know sometimes they are used interchangeably but for me resolution is the pixel dimension.

You can find out the dpi of you monitor by taking a tape measure and measure the width of the viewable screen. Divide the horizontal resolution by the inches. If you have the display set for 1920*1080 and the physical width is 22 inches it's about 87dpi.

My first computer was 72-- black and white,

Back then they were actually 72 DPI hence the reason 72DPI is still used as a standard for images. There is bit of history there if you want to research it. Currently the DPI setting in your OS has no relevance to the actual DPI setting being displayed.