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Less is More: The Orthodox File Manager (OFM) Paradigm

by Dr Nikolai Bezroukov

Content : Foreword : Ch01 : Ch02 : Ch03 : Ch04 : Ch05 : Ch06 : Ch07 : OFM1999 : OFM2004 : OFM2012


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Dos Navigator -- a breakthrough in VFS development

The DOS Navigator (DN) is an extremely interesting and influential early implementation of OFM. Since early 1999 it's an open source product. Before that it was shareware. The initial version was released in 1991.

I discover DN existence rather late when the dynamic phase of its development was well over. The first version that I checked was version 1.5 released in April 1997. See Youtube video: Dos Navigator 1.51 - inside DoSBox. Best File Manager on MS-DOS ever invented. It is still current in 1999 (build 002). At the same time analyses of previous versions and correspondence with one of the authors suggested that technically the DN was the leader (although not very widespread even in the xUSSR region) since early 1993 (from version 1.10).

By implementing three additional VFS DN opened a new generation of OFMs. Also unlimited number of panels and a lot of new important features make it one of the most powerful (and complex) OFM I ever encountered. It should be considered probably as an ultimate DOS-based classic implementation of OFM and it is difficult to compete with DN featurewise in DOS environment. It contains some useless or rarely used features, but until FAR no classic OFM could compete with it. Several other OFMs were influenced by DN design -- FAR was the most important example. Widespread usage of DN was partially damaged by the fact that it was distributed as shareware and not all features were available for unregistered users.

Like MC it is a team effort in RIT labs under the leadership of Stefan Tarnukov. The initial version of DN I (v 0.90) was released in 1991 and written by Stefan Tanurkov, Andrew Zabolotny and Sergey Melnik (all from Kishinev, Moldavia; Melnik is currently with Google, USA).

After that DN was rewritten using TurboVision by Stefan Tanurkov and Dmitry Dotsenko (currently in Moscow State University).  This versions are sometimes referred as DN II.  DN II was actively developed till the beginning of 1995 (until the  version 1.35 that should be considered as a milestone in the OFM implementations). 

Several other programmers participated in the development after the version 1.35. Starting from version 1.37 Slava Filimonov (he is now an author of the MRP Navigator - a file shell, designed for use for Win95/NT) and Ilya Bagdasarov were in charge of DN maintenance.   The version 1.5 was authored by Stefan Tanurkov and Max Masyutin.

In 1998 the development mostly took bugfixing direction as RITlabs new product  the Bat  became a more promising software product with much better commercial potential. So most material below is applicable to v.1.35 although I did not test it.

Although it is a text based OFM,  DN seems to be more close to GUI-based OFM implementations as it is using very refined  Borland Turbo Vision for the command line interface implementation. The size of DN distribution is also more close to GUI-based OFMs (1MB). Although it seems to be a little bit overloaded with additional utilities, the core OFM functionality is really impressive.

In late 1999 the authors released source code of DN  into public domain.  See DOS Navigator Open Source Project - Official Page (Lite version) for details. Several derivatives base on this codebase were created.

The most prominent among them is NDN (Necromancer's DN), currently in version 2.11.   NDN distributive was added to the Ultimate Boot CD. As of Sept 2012 current version NDN is 2.31.5309 releases 2010-03-23

DN Contributions

DN 1.35 should be considered as a milestone in the OFMs virtual file system implementations. It had made a very important contributions in this area. The feature set and flexibility of DN in this area are really amazing.

DN works with the Windows and OS/2 clipboard (Ctrl-Ins and Shift-Ins). Pressing Alt-/ you can switch between three modes: timed execution, execute OS/2 app in full screen and window (the last two are available under OS/2 only, obviously).

Among a long list of DN innovations I would like to single out the following three VFS:

This three new types of VFS were really a milestone in OFM development.  For example the Xtree VFS is a very important productivity enhancement tool, but regrettably very few OFMs implement it (for example FAR still lack it in v.1.6). From this point of view DN is still No.1 in Dos/Windows world.

Three other innovations are also very important:

As I already mentioned DN introduced many other innovations. Among them:

Viewer has several interesting features:

The built-in editor in DN is pretty decent, but without any macro facilities. IMHO for OFMs unless the editor is programmable and serve as a base of OFM implementation it probably should belong to QE class (QE or Quick Edit is one of the most famous DOS-based editor programmed in assembler -- a lot of power in 32K of code).

From that point of view the syntax highlighting is probably an overkill for the light-weight build-in editor as well as line drawing; an alternative (external) middle-weight or heavyweight editor should be used in complex cases. But that my point is clearly disputable. I am a MultiEdit editor user and judge everything from that point (I also know KEdit quite well). Many users including some of my most bright programming students never managed to learn a complex editor like MultiEdit and stick with simple solutions. For that class of users as well as users of Watcom C/C++ which don't have a DOS IDE and use DN as a programming environment syntax highlighting is a very useful feature indeed.

Another great thing in DN as a programming environment it that it is truly multi window. You can have any number of files open in editor/viewer windows, can call the calculator from anywhere etc. This is really great functionality that none other OFM come even close.

Among useful thing that can be implemented without much trouble in other OFMs built-in editors I would like to mention:

Level of compatibility

Despite a lot of enhancements semantically DN is still compatible with OFM doctrine and earned more than 66% on the part 1 of the OFM1999 standard. Most operations that I tested were implemented semantically correctly although some of them used different (e.i. non-standard) hot keys.

DN does not use WWW style enhancements.

Quick search of the file in the panel is somewhat nonstandard -- instead of classical for OFMs combination Alt-letter  (or Ctrl-Alt- letter for GOFM) DN use click on the Alt or Ctrl. After that DN is switched to the quick search mode and input of letters from the keyboard lead to quick search of the file with a given prefix.

Sometimes (like in case of switching from quick view windows to full windows view) no key was available at all and the operation need to be performed by the mouse. That is a deviation from the OFM doctrine that stress availability of all (or most) operations via hot keys. For other operation hot keys were different, so the major problem is that keyboard remapping is not supported.

The current version of DN supports archive VFS, but does not support DOS 7 long file names and FTP VFS.  No 32 bit version of DN exists yet.  As DN use TurboVision I believe it would not be difficult to convert DN into the GUI-based OFM. At the same time DN in compatible with


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