Towards a Resolution Resolution
And now, another definition deathmatch!
There are at least two common meanings. One refers to the absolute number of pixels in both the horizontal and vertical dimensions. The other refers to the pixel density, and is expressed in number of pixels per unit length, usually inches.
Can we please decide once and for all which one it is? Does the iPhone have a low resolution display at 320x480, or a high resolution display at 160 PPI?
I'm going to suggest that the first definition (that is, the horizontal and vertical pixel count) is more commonly-used and also has no convenient alternatives. Hence this should be the official definition of resolution. On the other hand, the term "pixel density" is a mostly reasonable substitute for resolution when this meaning is intended.
So what is often talked about as "resolution independence" isn't really. Apart from various oddities in Windows, most graphical interfaces have been independent of the number of pixels on the screen for some time now. Instead what is meant is more accurately described by the slightly ungainly phrase pixel density independence.
And that is a topic for next time...