BDOS — Basic Disk Operating System
MSXDOS.SYS, core of MSX-DOS, controls disk access and communications with peripherals. These MSXDOS.SYS functions are opened as “BDOS (Basic Disk Operating System)” so that the user can use them. Each routine opened is called a “system call”, which is useful in developping software for managing the disk (see section 4). Each execution is, however, not done by MSXDOS.SYS itself but DOS kernel. MSXDOS.SYS is an intermediation which arranges input/output requests from COMMAND.COM or external commands and passes them to the DOS kernel.
MSXDOS.SYS includes a portion called BIOS other than BDOS, as shown in Figure 3.2. BIOS, which has been prepared to be compatible with CP/M, is not normally used. Figure 3.2 MSXDOS.SYS
┌────────────┬───┐ │ BDOS │ │ ├────────────┤ │ MSXDOS.SYS │ BIOS │ │ └────────────┴───┘
The DOS kernel is the fundamental input/output routine which resides in the disk interface ROM and executes BDOS functions of MSXDOS.SYS. Actually, any system call function can be executed using the DOS kernel. DISK-BASIC executes system calls by calling the DOS kernel directly.