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

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 Sourceforge.net 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:

• Xtree VFS -- the ability to view a directory with all subdirectories as a single virtual directory. Drive a directory can then be viewed as a flat list of  files. This idea was pioneered in Xtree file manager and is a natural and very important extension of the OFM paradigm.  Filters on subtree are essentially a search function for subtree and in future implementations this two functions should be merged.

• Briefcase VFS that links to files and directories on existing drives into single virtual directory (or drive). Semantically it is an implementation of the link operation in UNIX, so a briefcase should be a standard feature in all UNIX implementations of OFMs. It is possible to copy files from different directories to the briefcase drive and then work with those links as if they are were stored on this drive. All file operations are supported.  Of course implementation of briefcase on a regular FAT file system is not as simple as in UNIX, but this is a Microsoft fault ;-).  For drives on some versions of MS DOS and all version of PC DOS join operation was available (strange mix of link and mount operations), so limited capability of creating briefcase was present even in DOS. There is no authomatic way to collect most recently viewed or edited files in briefcase or import them from the history.

• List-based VFS - the panel will show only files that are present in a special the text-file. This was a revolutionary generalization of the find file function and panel filters. Panel filters as currently implemented are not very useful. In DN the user activates list-based VFS using  Panel|Read. After getting the name of the file with the list DN will read the list, for example files.bbs, and search for each file present in the list. Much better way of implementing this feature would be probably generalization of panel filters. One need just to add the capability to read the specification of the filter from the file and to apply the filter to subtree rather than single directory.  The panel will display the list of files found. In DN files can be not only in different directories, but on different drives and that possibility should be preserved.  Here we see a difference between this VFS and Xtree VFS although they are somewhat similar and definitely can share considerable part of the implementation code. Again I would like to stress that OFM implementers just need to generalize filters to have this feature - an old concept can be extended into new domain.

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:

• The ability to have several sets of panels and switch between them like in a real multi-windows editor. Usefulness of the ability to have several sets of panels is proved by attempts by other authors to add similar features to OFM (for example early attempts to introduce 4 panels in the PIE Commander by Valentin Chernyak) and  experience with Windows-style file managers where multiple windows are a standard feature. 
• DN was probably the first OFM implementation that introduced keyboard macrorecoder in OFMs. DN permits to record a key sequence and replay it using an assigned hotkey.
• History lists for directory visited, selection masks, etc.
• Very powerful compare directories operation. It permits comparing contents -- a realyy useful feature You can choose to compare dates, times, attributes and contents.

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

• The first correct implementation of the panel information window concept. Lines in the panel information windows are customizable via file manager options menu. Default information windows in DN is a three line entity with a current file as the first line, the number of selected files is the second and number of files in the directory in the third line.
• According to Max Masyutin additional macro variables have existed in DN since 1991, i.e. they has been  implemented earlier that in VC.
• Several color styles that can be assigned to groups of extensions (file groups are provided by default).
• Movable panel delimiter can make the panels asymmetric so that one can view descriptions and additional columns on the single panel.
• Custom video modes (30-line panel view implementation).
• Drag and drop implementation for groups of files and single files (from information window) !
• Collapsible tree views (although I did not find the key to return to regular tree view);
• Directory tree has expand/collapse options: 
  • + : Expands/reads the tree starting at the current directory for one subdirectory level
  • - : Collapse the subdirectory tree below the current directory.
  • * : Expands/reads all subdirectories starting at the current directory.
• Persistent command history as an option
• Advanced file search:
• List of selection masks (e.g. *.bak; *.$$$; *.tmp ),
• Find words.
• Search inside archives.
• Find file not older that N days.
• Persistent  history for search.
• FileFind operation in DN can work in background.
• Some (limited) steps toward mask-selection language. DN does not use UNIX style regular expressions, but there is an option of negating the mask in the selection panel. Also there is a "mask construction windows" that can be displayed using Alt-Del. It seems to be somewhat similar to the FoxPro expression construction windows and permits constructing expression from several masks use negation for any single mask (JC solution seems to be simpler and more flexible, see below).
• Alt key activated top menu like in VC.
• Additional operations on selection lists.
• The ability to select files with the same name (Alt-Grey+);
• With the same extension (Ctrl-Shift-Gray+)
• With the same type (executable, etc) as the current file.
• The ability to select all file irregarding the file mask
• The ability to deselect all files irregarding the file mask
• The list of disks are displayed as the last line of information windows and there is an ability to switch from one disk to another by just clicking the disk letter with mouse (It is also possible to select next disk   using Ctrl-Left/Right  but I see no benefits from such an operation).
• Translation tables for built-in viewer (but there is no possibility to omit certain characters as in UFO).
• Operations with floppy images;
• The ability to edit commands history;
• New keys for selection of all files irregarding current selection mask, selecting all files with extension equal to the extension of the file under cursor, etc.

Viewer has several interesting features:

• Build-in calculator
• dump mode (with address button)
• Filter of ASCII characters

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:

• ASCII table;
• Jump operation;
• Two types of blocks (line blocks and stream blocks);
• Insert Date and Time operation;
• Change case command (for words and blocks).

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

Webliography

• DOS Navigator Open Source Project
• Dos Navigator support by RIT Research Labs
• DOS Navigator
• Dos Navigator - Wikipedia, the free encyclopedia
• Download Necromancer's Dos Navigator 2.15.5814 for Linux ...
• Necromancer's DOS Navigator
• freshmeat.net Project details for Necromancer's Dos Navigator

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Last modified: March 12, 2019