CP/M#Basic Disk Operating System

BDOS stands for Basic Disk Operating System and refers to the kernel of the operating system of Digital Research Inc. He is in all versions of CP / M and MS- DOS-compatible successor DR DOS use.


As an example applies the structure of CP / M in several shells. This concept was usually taken in the following operating systems. It is at the core of the actual hardware that is used by the I / O core directly. With the CP / M BIOS This first dish is called (English Basic Input Output System ) or MP / M and DOS Plus XIOS (English eXtended Input Output System ) and had to be written for each supported computer hardware-related. On the BIOS is based as a second shell of BDOS kernel and provides a variety of basic functions ( such as the file system ) for the actual operating system. The third shell is then the actual operating system or what a user sees it. In the 1970s and 1980s, it consisted mainly of a command line interpreter, Digital Research CCP (English Console Command Processor ) refers. Gary Kildall is considered the inventor of the method to encapsulate low-level programming to keep in further consequence the porting effort to a minimum. In CP / M Version 1.3 (1975 ) he described the first two shells, the BIOS and the BDOS kernel, as Floppy Disk Operating System, FDOS short.

How could, for example, CP / M to run the most famous operating system from Digital Research in the 1970s and 1980s on a variety of computers. Adapted only the BIOS / XIOS were each so BDOS and CCP could be used on various not mutually compatible systems.

See also: BIOS for CP / M computers

Technically were shifted with each new version of BDOS parts for the floppy controller driving each of the BDOS kernel in the BIOS to make the support for different disk drives more portable. This was especially apparent with the very successful version 2 of CP / M, which was adapted by many OEMs for their controllers and usually sold under a different name along with the hardware.

With the introduction of the IBM PC and its implemented in the firmware BIOS eliminates the need for a specially adapted as a first shell BIOS / XIOS. Later CP / M operating systems and their successors, however, continue to be based on BDOS as a kernel, such as DR DOS.

The last and most advanced operating system with BDOS kernel is the book published in 1993 Novell DOS 7 and its direct further developments OpenDOS 7:01 and 7:02 to DR-DOS DR-DOS 8.1 (DR- DOS 8.0 and 8.1, however, were withdrawn ). Already the BDOS kernel of MP / M or multi-user DOS offered true multitasking in a CP / M kernel. With BDOS 7.2 (Novell DOS 7 ) under a DOS kernel was first real pre - emptive multitasking possible.

BDOS versions in Digital Research operating systems

Since all operating systems from Digital Research BDOS use a kernel that BDOS version on operating systems and product boundaries is the same. About a BDOS function call the kernel version, like the one system ( 8080, Z80, 68000, 8088/8086, etc.) and operating system (CP / M, Multi User, Concurrent etc. ) can be read.

This partial list shows the relation of the BDOS kernel with each operating system:


Under CP / M BIOS was settled as a backbone in the form of an assembler file as a proposal to original equipment manufacturers (OEMs) and had to be specially adapted for the respective computer system. Through the backbone of this process, however, was immensely facilitated, which meant that CP / M was also sold in versions 1.4 and 2.2 separately.

Under DR DOS is called the IBMBIO.COM file. As it is written for the IBM PC, eliminating a costly custom BIOS as the first shell. Yet hardware functions shall continue in this file, which essentially corresponds to IO.SYS of MS -DOS and is further referred to as "BIOS". The BIOS file in IBMBIO.COM (thus in software) is not to be confused with the firmware BIOS of the IBM PC.


Under DR DOS is the BDOS kernel in the IBMDOS.COM file and is loaded into the memory resident. The kernel corresponds to the second shell; whose aim was to support each system to be compilable, since its functions were the first cup each specially adapted support ( BIOS ).

Under CP / M BDOS the kernel was settled as an object file to original equipment manufacturers ( OEMs ) have the kernel with the customized BIOS after compiling ( Compile ) left and then spread along with the hardware. Even when sold to individuals version of CP / M en CP / M operating system was buildable in this way.