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MSX-DOS
MSX-DOS is a discontinued disk operating system developed by Microsoft for the 8-bit home computer standard MSX, and is a cross between MS-DOS 1.25 and CP/M-80 2.
==MSX-DOS==
MSX-DOS and the extended BASIC with 3½-inch floppy disk support (known as MSX DOS Disk Operating System) were simultaneously developed by Microsoft and Spectravideo as a software and hardware standard for the home computer MSX standard, to add disk capabilities to BASIC and to give the system a cheaper software medium than Memory Cartridges, and a more powerful storage system than cassette tape (See SVI MSX User Manual (M-246) 1985 (Spectravideo MSX DOS Disk Operating System) Introduction to MSX DOS section 1.3). The standard BIOS of an unexpanded MSX computer did not have any floppy disk support, so the additional floppy disk expansion system came with its own BIOS extension ROM (built-in on the disk controller) called the BDOS. Spectravideo also released an MSX-DOS disk, in conjunction with the SVI-707 which could be Loaded into your MSX System. Once MSX-DOS had been Loaded, the system searches the MSX-DOS disk for the COMMAND.COM file ald loads it into memory (See SVI MSX User Manual (M-246) 1985 (Spectravideo MSX DOS Disk Operating System) Getting Started section 2.1).It not only added floppy disk support commands to MSX BASIC, but also a booting system, with which it was possible to boot a real disk operating system. In that case, the BDOS bypassed the BASIC ROMs, so that the whole 64 KB of address space of the Z80 microprocessor inside the MSX computer could be used for the DOS or for other boot-able disks, for example disk based games. At the same time, the original BIOS ROMs could still be accessed through a "memory bank switch" mechanism, so the DOS-based software could still use BIOS calls to control the hardware and other software mechanisms the main ROMs supplied. Also, because of the BDOS ROM, basic file access capacity was available even without a command interpreter by using the BASIC extended commands.
One major difference between MSX-DOS and MS-DOS 2.x was that MSX-DOS did not use the "boot sector" on the floppy to boot, but booted using the BDOS ROM routines, and, in a fashion much like MS-DOS 1.25, it used the FAT ID value from the first byte of the FAT to select file system parameter profiles for its FAT12 file system instead of from the BIOS Parameter Block (BPB) in the bootsector. Also, because there could be more than one floppy disk controller in two or more cartridge slots, MSX-DOS could boot from several different floppy disk drives. This meant that it was possible to have both, a 5¼" floppy disk drive and a 3½" disk drive, and the user could boot from either one of them depending on which drive had a bootable floppy in it.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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