weeeeell, in the beginning, IBM built the color graphics adapter, with its CGA video display standard. the old-fashioned teletypes printed on paper which had, conceptually, endless length. there was no standard for the width, but it usually accomodated well over 120 columns, which was too much for the tiny (typically around 12") monitors they had back then, so IBM chose to go for 80 columns, just because that happened to be the number of columns on their paper punch cards.

consequently, the graphics resolution had to be a multiple of 80, and 8 pixels per character seemed to be about the minimum for a somewhat nice font. due to the restrictions of the width/height-ratios of fonts and screens, the number of lines in text mode was fixed at 25, so the CGA resolution is 640x200 with 1bit colour. there also is a commodore-like 40x25 text mode with a corresponding graphics resolution of 320x200 pixels at 2bit colour. because the pixels are almost square and there are more colours in this mode, it is much more useful for graphics.

in fact, 320 x 200 proved to be a very useful order of magnitude, pixel-wise, for a long time, because computers couldn't handle more with a decent number of colours. while EGA (640 x 350) at 4bit, made possible with the enhanced graphics adapter, was often used as a compromise in its time, it was a rather ugly compromise. but VGA (video graphics array) adapters, with their 640 x 480, could display the 320 x 200 at 8bit colours, which was, for most applciations at that time, pretty much all the colours you could ask for. those additional 80 pixels in the vertical dimension were introduced to finally make the pixels square instead of square-ish at the desired 4:3 aspect ratio. and it has exactly the same number of visible lines as the NTSC standard (which actually has 525 lines, but you can't see them all).

the cool thing about VGA adapters is that you can make them, with a little trickery like mode-x, display 320x240 square pixels at 8bit colours. one or two crazy people call this quarter VGA, or QVGA.

four times VGA resolution would be 1280x960, but for a long time, designers of devices that handle pixels in some way were more concerned with utilising the scant memory capacities as good as possible and generally having binary-friendly numbers. consequently, they slowly progressed over super VGA, i.e. SVGA (800 x 600), to the extended graphics array, i.e. XGA (1024 x 768). all was nice and well, with square pixels, until some idiot fixed SXGA (a.k.a. UVGA or, even rarer, XVGA) at 1280 x 1024 pixels.

the first corresponding PC graphics boards could typically display these resolutions at 16bit colours, a compromise made, again, for the sake of optimised memory utilisation. for older adapters, the bit depth limited the number of colours you could see at once, but you actually could choose from a bigger palette. on a VGA adapter, the palette lets you specify individual colours with 8 bits per component (i.e. red, green and blue), making for a total of 16,777,216 colours. newer adaptors can display arbitrary combinations out of these colurs in one frame. this is 24bit colour (sometimes also called 32bit for no good reason) and usually available for all resolutions mentioned below and nowadays also for those mentioned in this paragraph). 16bit also works like this, without a palette, but you only get 6 bits for the green channel and only 5 for red and blue, respectively (the human eye is more sensitive in the green spectrum). that's only 65,536 colours, and virtually non of them coincide with colours available in 24bit mode, which caused a lot of trouble and inspired bullshit like the "web safe palette".

PC users, who deal with rather ordinary monitors and graphics boards, might think that sanity was finally restored with ultra XGA, i.e. UXGA 1600x1200. however, with the introduction of less ordinary devices, particularly wide screens in different aspect ratios, and the demand for higher resolutions, the creation of marketese-compatible abbreviations began to rampage. fixing SXGA wide at 1600x1024 pixels is a silly idea to begin with, but logical, given the stupid, stupid aspect ratio of SXGA. with about the same logic, manufacturers never decided wheter to call the beast SXGAW, SXGA-W, WSXGA, or W-SXGA.

the term HDTV is as crystal clear as the corresponding picture wants to be and 1920x1080 is exactly 16:9. this is even much nicer than the old, analog HDTV specifications. back then, the analog standard in the US was 1920x1035, but the pedantic germans and the opinionated french wanted their own PAL and SECAM, respectively, -derived HDTV to be 1920x1152 (twice the vertical resolution of their signals, which have invisible lines anyway, don't ask). by the way, MPEG-2, the compression algorithm used for transmitting digital HDTV signals, requires the resolution's pixel counts to be multiples of 16. while the old european analog standard features exactly such a resolution, the new digital HDTV standard does not. what the hell, at least 16:9 is easier to write than 1¹/₃:1. anyway, we know that everything was sorted out nicely in the end on the TV side, and on the computer side, as expected, you have to display HDTV signals at UXGA wide 1920x1200, to ensure compatibility with the naming scheme, which is at least flexible enough to let you choose between UXGAW, UXGA-W, WUXGA, and W-UXGA.

above that, there's also quad XGA, quad SXGA (yuck!) and quad UXGA. you can surely figure out the respective abbreviations and resolutions yourself. there's also QUXGAW, of course, which can also be called... well, you know. now we come into the range of 'quad quad' resolutions, which are called hexadecimal resolutions, like hexadecimal SXGA, which has, at 5120x4096, exactly 16 times the pixel count of SXGA, making the pixels' aspect ratio exactly yuck!². masochists may write down the alternate names for HSXGAW now. yes, it's 6400 pixels wide, just as the much nicer HUXGA. HUXGAW (or, you know...), by the way, has over 36 megapixels.

in order to take full advantage of 36 megapixels, the display has to be so big (or you have to be so close to it), that you can barely see the whole surface without moving not only your eyes, but your whole head around. once we actually need 36 megapixels, we'll use HUXGAW, and all will be fine. and for now we'll just use UXGA, and all is fine, too.

except when we need a wide screen. in this case, i'd recommend leaving the PC world altogether and buying a mac. now that should have eliminated all clarities.

anyway, to finally answer your question: HSXGA-W obviously is called that way and has 6400 x 4096 pixels and 1 by 1.171875 pixels because of the punch cards.