if a TV is 720p...?

Question

that means that it displays 720 vertical lines. Vertical lines run from the top to the bottom, and they are placed next to each other. So a 720p TV should have 720 vertical lines, so it's 720 lines wide. how long the lines are defines the height of the TV. so when they say a TV has a resolution of 1024x720, isn't that saying that it has 1024 pixels across and 720 pixels from top to bottom? wouldn't this be capable of displaying 1024 vertical lines, or possibly 720 horizontal lines?
is it not the case that a 1024x720 screen has 1024 columns and 720 rows? which is why it is wider than it is high, i.e. 16x9 is 16units wide and 9units high.
I just don't understand why a 720p TV doesn't have 720 pixels counting from left to right, but it has 720 pixels counting from top to bottom, and claims only 720 vertical lines

Answer 1

You seem to have a conceptual error on what "vertical lines of resolution" means. It doesn't mean that there are 720 vertical lines (obviously, because we're talking about the top-to-bottom dimension, not the side-to-side).

What it means is that the picture can display 720 distinct horizontal lines of a picture in the vertical direction (720 lines stacked one on top of another). The 1024 horizontal lines means that, going horizontally across the screen, the picture can can display 1024 distinct vertical lines. These lines would be, for example, in a test pattern that is displayed on the screen.

Answer 2

Everything you say is correct. The reason a flat panel set is designated by the number of pixels counted from top to bottom is a hold-over from the CRT days when the picture was created by sweeping actual lines across the screen. Hence the re4solution was in terms of the number of lines counted from top to bottom. In flat panels, the picture is not created by "drawing" lines on the screen. The processors create a matrix so many pixels high and so many pixels long that represents the picture and sends that to the screen. The spacing of the pixels is, in most cases the same, up and down and left to right. In this way, you get a nice even picture. So, the ratio of vertical to horizontal pixels is the same as the ratio of screen height to width.
There are exceptions. Some TVs have oddball pixel ratios. So you should always check the ratio to see if it is the same. BTW, most 720 sets are actually 768 pixels vertically. A 720P video signal is processed to fill-in the extra pixels, both vertically and horizontally.