DOS Plus

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DOS Plus
DR DOS

DOS Plus (erroneously also known as DOS+) was the first

DR DOS
.

DOS Plus is able to run programs written for either CP/M-86 or

MS-DOS 2.11, and can read and write the floppy formats used by both of these systems. Up to four CP/M-86 programs can be multitasked, but only one DOS
program can be run at a time.

User interface

DOS Plus attempts to present the same

command-line interpreter called COMMAND.COM (alternative name DOSPLUS.COM). There is an AUTOEXEC.BAT file, but no CONFIG.SYS (except for FIDDLOAD, an extension to load some field-installable device drivers
(FIDD) in some versions of DOS Plus 2.1). The major difference the user will notice is that the bottom line of the screen contains status information similar to: 

DDT86    ALARM                  UK8 PRN=LPT1      Num    10:17:30

The left-hand side of the status bar shows running processes. The leftmost one will be visible on the screen; the others (if any) are running in the background. The right-hand side shows the keyboard layout in use (UK8 in the above example), the printer port assignment, the keyboard Caps Lock and Num Lock status, and the current time. If a DOS program is running, the status line is not shown. DOS programs cannot be run in the background.

The keyboard layout in use can be changed by pressing Ctrl, Alt and one of the function keys F1–F5.

Commands

DOS Plus contains a number of extra commands to support its multitasking features:

It also contains subsets of the standard

COPY command, and a PIP
utility, both of which copy files.

The

CD command can assign one of the three drives N:, O: or P: to a directory on a different drive, in a similar manner to the MS-DOS command SUBST
. For example, 

CD N:=C:\DATA\ACCOUNTS

will cause the directory C:\DATA\ACCOUNTS to appear as drive N:. This so-called

command prompt
much easier. This feature is also present in
NDOS command processor supports this features as well.[4] Floating drives are implemented in the BDOS kernel, not in the command line shell, thus this feature can also be used from within DOS applications when entering directory paths
for as long as the application does not parse and split the dirspec for further processing.

Using a similar feature, Concurrent DOS, Multiuser DOS, System Manager and REAL/32 will dynamically assign a floating drive L: to the load path of a loaded application, thereby allowing applications to refer to files residing in their load directory under a standardized drive letter instead of under a fixed absolute path. This

load drive
feature makes it much easier to move software installations on and across disks without having to adapt paths to overlays, configuration files or user data stored in the load directory or subsequent directories. (For similar reasons, the appendage to the environment block associated with loaded applications under MS-DOS/PC DOS 3.0 (and higher) contains a reference to the load path of the executable, however, this consumes more resident memory, and to take advantage of it, support for it must be coded into the executable, whereas DRI's solutions transparently works with any kind of application.)

Another feature resulting from the BDOS' internal organization of current working directories as relative links to parent directories is the theoretically unlimited directory depth supported by all those above mentioned operating systems – in contrast to MS-DOS/PC DOS (and DR DOS since 1992), where an MS-DOS compatible internal data structure named

Current Directory Structure
(CDS) limits directory depths to a maximum of 66 characters.

These features can be attributed to the fact that CP/M itself did not have a concept of subdirectories, and DOS was emulated under these operating systems, so directories had to be translated to internal CP/M structures in some intelligent way.

Internal structure

DOS Plus boots from a single file called either DOSPLUS.SYS or NETPLUS.SYS (rather than the IO.SYS / MSDOS.SYS combination of MS-DOS). This file is in the CP/M-86 CMD format, and is structured internally as a number of modules:

Computers that used DOS Plus

DOS Plus was the main operating system in ROM for the

Acorn 286
prototypes were supported as well.

Versions

Known operating system versions include:

See also

  • Personal CP/M-86 2.0
    (with BDOS 4.1)
  • Personal CP/M-86 2.11
    (with BDOS 4.1)
  • CP/M-86 Plus
  • MSX-DOS
  • GEMDOS
  • GEM XM

Notes

  1. ^ a b This version does not implement the S_OSVER call and thus cannot be queried for its actual version number.

References

  1. ^ a b c d e Wein, Josef "Joe" (2010-02-19) [November 2009]. Johnson, Herbert R. (ed.). "DRI History and Joe Wein". Archived from the original on 2017-01-17. Retrieved 2017-01-17.
  2. Kotulla, Martin (November 1987). "Von CP/M zu MS-DOS, Teil 11" (PDF). Professional Computing (PC) - Schneider International (in German). 3 (11): 100–103. Archived
    (PDF) from the original on 2019-04-24. Retrieved 2018-05-20.
  3. ^ Paul, Matthias R. (2002-03-26). "Updated CLS posted". freedos-dev mailing list. Archived from the original on 2018-10-04. Retrieved 2014-08-06.
  4. 4DOS 8.00 online help
    .
  5. ^ Paul, Matthias R. (2002-02-20). "How to detect FreeCOM/FreeDOS in-batch?". freedos-dev mailing list. Archived from the original on 2014-08-12. Retrieved 2014-08-06.
  6. OpenDOS 7.01, including the description of many undocumented features and internals. It is part of the author's yet larger MPDOSTIP.ZIP collection maintained up to 2001 and distributed on many sites at the time. The provided link points to a HTML-converted older version of the NWDOSTIP.TXT file.) [1]
  7. Macintosh
    . […]
  8. ISSN 0753-6968. Archived from the original on 2020-02-17. Retrieved 2020-02-17. […] Système d'exploitation: DOS-Plus et MS-DOS 2.11. […] [2][3]
  9. ^
    512. The material is the property and copyright of Digital Research, not of Acorn Computers. This is further complicated by the fact that four different versions have actually been issued. […] There have been several versions of DOS Plus for the 512, version 2.1 being the latest issue. […] [4]
  10. ^ a b "The BBC Master 512 - DOS-Plus and GEM System Software". Yellow Pig's BBC Computer Pages. Archived from the original on 2018-05-20. Retrieved 2018-05-20.
  11. ^
    ISBN 1870336143. Archived
    from the original on 2018-05-20. Retrieved 2018-05-20.
  12. Philips Austria. This file contains additional information on the use of DOS Plus 1.1 on the :YES
    Rel 1 and :YES Rel 2.

Further reading

External links
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