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DOS/V was a Japanese computing initiative starting in 1990 to allow DOS on IBM PC compatibles with VGA cards to handle double-byte (DBCS) Japanese text via software alone. It was developed by IBM for its PS/55 machines (a localized version of the PS/2).Kanji fonts and other locale information were stored on the hard disk rather than on special chips as in the preceding AX architecture. As with AX, its great value for the Japanese computing industry was in allowing compatibility with foreign software. This had not been possible under NEC's proprietary PC-98 system, which was the market leader before DOS/V emerged. DOS/V stands for "Disk Operating System/VGA" (not "version 5"; DOS/V came out at approximately the same time as DOS 5).
Previous Japanese IBM DOS required an IBM proprietary video adapter
In early 1980s, IBM Japan released two x86-based personal computer lines for Asian-pacific region, IBM 5550 and IBM JX. The 5550 read Kanji fonts from the disk, and drew text as graphic characters on 1024×768 high resolution monitor. The JX extended IBM PCjr and IBM PC architecture. It supported English and Japanese version of PC DOS with 720×512 resolution monitor. Both machines couldn't break dominant NEC's PC-98 in consumer market in Japan. Because the 5550 was expensive, it was mostly sold for large enterprises who used IBM mainframes. The JX used 8088 processor instead of faster 8086 processor because IBM thought a consumer product of JX mustn't surpass a business-class 5550. It damaged buyer's reputations whatever the actual speed was. In another point, a software company said IBM was uncooperative for developing JX software. IBM Japan planned a 100% PC/XT compatible machine codenamed "JX2", but it was cancelled in 1986.
Masahiko Hatori(羽鳥 正彦) was a developer of JX's DOS. In 1987, he started developing DOS/V during spare time at IBM Yamato Development Laboratory. In this era, Toshiba released J-3100 (a Japanese version of T3100 laptop) and Microsoft introduced the AX architecture. A few months later, IBM Japan released PS/55 Model 5535 which was a proprietary laptop using a special version of DOS. Hatori thought IBM needed to shift their own proprietary PC to IBM PC compatibles. His bosses, Tsutomu Maruyama(丸山 力) and Nobuo Mii, thought Japan's closed PC market needed to be changed and this attempt couldn't be done by IBM alone. In summer of 1989, they decided to carry out development of DOS/V, disclose the architecture of PS/55, and found the PC Open Architecture Developers' Group (OADG).
The DOS/V development team designed the DOS/V to be simple for better scalability and compatibility with original PC DOS. They had difficulty reducing text drawing time. "A stopwatch was a necessity for DOS/V development", Hatori said.
The first version of DOS/V was introduced on 11 October 1990, and shipped out in November 1990. The announcement letter said it was designed for low-end desktops and laptops of PS/55, but users reported on BBS that they could run DOS/V on IBM PC clones. The development team confirmed these comments and modified incompatibilities of DOS/V. It was a secret inside the company because it would prevent sales of PS/55 and meet with opposition. Hatori said,
We hid the DOS/V run on other IBM compatible machines. The fact was that we developed it could run on Gateway's and any machines, but we had to keep the secret, not to spread it, because there are lots of enemies inside the company. In short, it was a double-edged sword. If the DOS/V run on such cheap compatible machines, conversely the 5550 series which had taken high profit up may not be sold. In fact, 80% of staff in Yamato office opposed it.
Maruyama and Mii had to convince IBM's branches to agree with the plan. In the beginning of December 1990, Maruyama went to IBM's Management Committee, and presented his plan "The low-end PC strategy in Japan". At the committee, a topic usually took 15 minutes, but his topic took an hour. The plan was finally approved by John Akers.
After the committee, Microsoft Japan got a contract with IBM Japan to receive source code of DOS/V. On 20 December 1990, IBM Japan announced they founded OADG and Microsoft would supply DOS/V for other PC manufacturers. From 1992 to 1994, most Japanese manufacturers begun selling IBM PC clones with DOS/V. Some global manufacturers entered into the Japanese market, Compaq in 1992 and Dell in 1993. Fujitsu released IBM PC clones (FMV series) on October 1993, and about 200,000 units were shipped in 1994. Microsoft Japan released first retail versions of Windows (Windows 3.1) for both DOS/V and PC-98.
The DOS/V contributed the dawn of IBM PC clones in Japan, yet PC-98 had kept 50% of market share until 1996. It was changed by the release of Windows 95.
The development of MS-DOS 5.0/V was delayed because IBM and Microsoft disputed how to implement the API of input methods. They couldn't make an agreement, so MS-DOS had KKCFUNC.SYS while PC DOS had $IAS.SYS. Compaq didn't participate in OADG. They developed own DOS/V drivers, and released their first DOS/V computers in April 1992.
^ abIBM Japan (1990-10-11). PS/55に業界最高速モデル登場 [The industry's fastest model is now added on PS/55]. Jōhō Kagaku 情報科学 (in Japanese). ja:情報科学研究所 (published 1991). 27: 53–61. ISSN0368-3354. Retrieved 2018-06-29.
^Izumi, Yu, ed. (2006-06-11) [2001-03-03]. DR DOS 7.0x/V 非公式インストールマニュアル - 管理人関係リンク [DR DOS 7.0x/V - Unofficial installation, manual administration, links]. 4.7.4 (in Japanese). Japanese DR DOS User's Group (JDUG). Archived from the original on 2018-09-16. Retrieved 2020-03-06.