I recently ran into an interesting difference in the way various DOS/V versions manage VGA memory. DOS/V of course refers to the Japanese versions of DOS which are capable of running on standard “Western” hardware.
Microsoft has a very long history of supporting the Far East (how they used to be called) markets, especially Japanese and Korean, going back to the early 1980s. At that time, standard PC hardware was simply not capable of displaying Kanji ideographs; MDA had no user-definable fonts, and CGA had woefully low resolution. Systems tailored to the Japanese market used custom hardware, more or less incompatible with IBM PCs.
Once the VGA appeared, the technology was capable of emulating text modes using a relatively high resolution (for the time) graphics mode. MS-DOS/V versions 5.0 and 6.2 (released in March and December 1993, respectively; further referred to as DOS/V) both used a 640×475 graphics mode, slightly unusual but logical. The character cell was 19 pixels high and 8 or 16 pixels wide (Kanji ideographs, usually encoded as two bytes, were also displayed twice as wide as standard ASCII characters). To display an 80×25 text mode using a 19 by 8 pixel character cell, a 640×475 resolution is required. That’s not quite the same as the standard 640×480 VGA resolution, but it’s the closest lower resolution usable for relatively detailed glyphs and 80×25 grid. Continue reading
