13 Compatibility

 The HDFS is compatible with DNFS, but not identical. Most of the commands
are the same, but there are some differences. These are:

 Unsupported commands.
The following commands are not supported:

 *BACKUP, *DESTROY, and *LIST. *BACKUP is replaced by the new syntax for
*COPY, and *DESTROY is replaced by the option to *WIPE. *LIST was not used
much, and is not replaced.

 Abbreviations.
The differences in the filing system commands means that some
abbreviations which work with DNFS (e.g. *DE.) will not work with HDFS.
The safe method is to use full command names.

 Utility commands.
The DNFS utility commands *BUILD, *DUMP, and *TYPE are filing system
commands in HDFS, which means that they can only be used when HDFS is
active. The line length on *BUILD is limited to 63 characters.

 Command syntax.
There are a few syntax changes. *CAT and *COMPACT take a directory as an
argument instead of a drive. The syntax for *COPY and *RENAME has changed,
so that they take two file specifications or an ambiguous file
specification and a directory specification instead of two drive numbers
and an ambiguous file specification.

 A space is needed after all HDFS commands, where it was not necessary in
DNFS e.g. , *DIR :0 instead of *DIR:0.

 File name syntax.
The single character match wildcard in HDFS is normally '?', instead of
the '#' used for DNFS. It can be changed with the *WILD command if
necessary . The '$' and '^' characters are also special in HDFS.

 No enabling.
The *ENABLE command is provided, but is not required by HDFS.

 Spooled output.
HDFS is not re-entrant, and so it turns off output to the *SPOOL file in
certain circumstances which could cause race conditions. Most DNFS output
can be spooled.

 Catalogue Reporting.
The format of the catalogue displayed by HDFS is slightly different than
DNFS. The current directory and library take more space, and the directory
start sector has been added to the information. File permissions are
reported differently, because HDFS supports permissions for reading,
writing, and executing files.

 Display modes.
HDFS makes full use of the 80 column modes. Catalogues and data dumps use
the full width of the screen, whereas DNFS just produces 40 column output
whatever the display mode.

 The same memory areas are used by HDFS and DNFS; see appendix F for
details of the HDFS memory usage.

 Some copy protection schemes which were designed to run under DNFS may
not initially work with DNFS, because of the auto-stepping and sector
number checking features. The extra parameters to the *DRIVE command can
be used to disable sector checking, and set the step rate to single or
double stepping to allow these schemes to work. The OSWORD &7F command for
access to the 8271 disc controller chip is fully supported by the HDFS.