ng systems.
The first of these attempts consisted in DOS Plus 1.2-2.1 (1986–1988), a single-user descendant of DR Concurrent PC DOS 4.1-5.0, which runs PC-DOS 2.11 applications in addition to CP / M-86 applications could and was available for a handful of OEM platforms. As an emulation based on a CP / M kernel, however, DOS compatibility was still limited. a. since many commands were still similar to CP / M and z. B. no DOS device drivers could be loaded.
Digital Research started the next and ultimately successful attempt in 1988 with the presentation of DR DOS 3.31 (with BDOS kernel 6.0) in a phase when the further development of MS-DOS / PC DOS at Microsoft and IBM seemed to be stagnating and urgently needed adjustments were being made the possibilities of newer machines were dragged there over the years. This new single-user operating system line was a spin-off from Concurrent DOS 6.0, in which the XIOS was replaced by an IBM PC-compatible DOS BIOS in order to achieve maximum compatibility with the boot phase of DOS and with DOS device drivers . A CP / M-like BDOS kernel was still working inside, but it was no longer compatible with CP / M system calls and was pretending to be IBM PC DOS 3.31. The system offered no multitasking, but almost 100% compatibility with DOS applications, which with the MS-DOS editions common up to now, overdue support for the management (at that time) of "large" hard disks (based on the Compaq MS-DOS 3.31 model ), as well as a number of enhancements compared to the competition MS-DOS, such as password-based access control for files and directories, floating drives, subdirectories that can be nested as deeply as required, a command line and input history function that is effective everywhere, meaningful error messages and extended help functions.
DR DOS was able to survive several versions (DR DOS 3.31, 3.32, 3.33, 3.34, 3.35 with BDOS 6.0, DR DOS 3.40, DR DOS 3.41 with BDOS 6.3, DR DOS 5.0 with BDOS 6.5, DR DOS 6.0 with BDOS 6.7) powerful alternative to MS-DOS and PC DOS claim. From this point onwards, many of the fundamentally new functions (including memory management, task switching, GUI, disk compression, deletion tracking) were first implemented in DR DOS and in some cases only years later in MS-DOS and PC DOS. The compatibility with unclean DOS applications was also increasingly improved, until finally in 1992 with DR PalmDOS 1.0 (BDOS 7.0) the previous DOS emulation of the kernel was completely replaced by DOS-compatible internal structures. DR PalmDOS was a further development of DR DOS 6.0 with special functions for early palmtops such as an integrated PCMCIA stack, the possibility of executing XIP applications under a special task switcher variant directly from the ROM, and including extended energy management a dynamically effective idling detection. For reasons of compatibility, all previous editions of DR DOS for normal DOS applications are PC DOS 3.31.
After Digital Research was sold to Novell in 1993, the system was marketed in 1994 as Novell DOS 7 (with BDOS 7.2), which for DOS applications was PC DOS 6.1. In addition to peer-to-peer network functions ( Personal NetWare ), Novell DOS 7 offered greatly expanded memory management with VCPI, DPMI and DPMS and, in conjunction with a 32-bit protected mode core system provided via EMM386, support for preemptive multitasking and multithreading in DOS virtual machines.
After more than 15 updates, the system was sold to Caldera in 1996, who re-released it in 1997 as Caldera OpenDOS 7.01. The source code of the core components was also published (only usable for non-commercial purposes) as well as historical source code from CP / M, GEM and ViewMAX . Caldera UK developed the system under the name DR-DOS (now for the first time written with a hyphen) to DR-DOS 7.02 and 7.03 (BDOS 7.3) with year 2000 fixes, euro support and some new upload functions, versions that in addition to some larger extensions that are not included in all editions (such as TCP / IP support, the graphical HTML 3.2 web browser WebSpyder, support for long file names