Apple II
File Type Notes
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                                                  Developer Technical Support

File Type:         $E0 (224)
Auxiliary Type:    $8004

Full Name:     Davex archived volume
Short Name:    Davex archived volume

Written by:    Dave Lyons                                            May 1990

Files of this type and auxiliary type contain an archived image of a ProDOS 
volume.
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Davex is a ProDOS 8 command-line shell and program launcher compatible with 
all Apple II computers that can run ProDOS 8.  It supports stuff like 
wildcards, command history, print spooling, sorted directory listings, and 
operations on whole directory structures.  You can add your own assembly-
language commands, too.  Davex also allows (coincidentally) saving an image of 
any ProDOS volume into a file and restoring it later.

For more information on Davex, contact:

    DAL Systems
    P.O. Box 875
    Cupertino, CA 95014
    Attention:  Davex Technical Support


File Structure

The first 512 bytes of a Davex archived volume are a header, described under 
"File Format" in this Note.  After the header comes 512 bytes for each block 
on the saved volume, from zero on up.  For blocks that are unused, you can 
just set the file mark ahead 512 bytes instead of writing 512 zero bytes--this 
way the unused blocks do not take up disk space, so the resulting file is only 
a few blocks larger than the number of used blocks on the original volume.

If you run out of room while you are creating an archived volume file, close 
the file and start another one with the same name on a new disk.  The 
fileNumber field in the header is one in the first file, two in the second 
file, and so on.

This file format is suitable for ProDOS, but it is less useful on a file 
system (such as AppleShare) that does not allow for sparse files.  A Davex 
archived volume file on an AppleShare server always takes up more blocks than 
the original volume contains.

File Format

identityCheck (+000)    16 Bytes        These 16 bytes are 
                                        required for historical reasons 
                                        (there didn't used to be a special 
                                        file type and auxiliary type to 
                                        identify these files).  The required 
                                        value is $60 followed by "VSTORE 
                                        [Davex]" and a $00.  The characters 
                                        have their high bits off.
fileFormat    (+016)    Byte            Must be $00.  A nonzero value 
                                        means the file format has changed in 
                                        a way that isn't compatible with the 
                                        current definition.
vstoreVers    (+017)    Byte            Version of Davex vstore 
                                        command used to create this file 
                                        (others use $00).
vrestoreVers  (+018)    Byte            Minimum version of the Davex 
                                        vrestore command needed to read this 
                                        file.  Use $10 (version 1.0).
reserved      (+019)    13 Bytes        Reserved for future use.
deviceNum     (+032)    Byte            ProDOS 8 device number of the 
                                        device that this file is a volume 
                                        image from.  Informational only.
totalBlocks   (+033)    Long            Number of blocks on the saved 
                                        volume.
usedBlocks    (+037)    Long            Number of used blocks on the 
                                        saved volume.
volumeName    (+041)    String          Name of the saved 
                                        volume, with a leading length byte.  
                                        This field is 16 bytes long.  If the 
                                        name is shorter than 15 characters, 
                                        the remaining bytes are unused and 
                                        should be zero.
reserved      (+057)    7 Bytes         Reserved for future use.
fileNumber    (+064)    Byte            This field contains one for 
                                        the first file of an archive, n in 
                                        the nth file (see above).
startingBlock (+065)    Long            Block number corresponding to 
                                        the data starting at offset (+512) 
                                        in this file.
reserved      (+069)    443 Bytes       Reserved for future use.
theBlocks    (+512)     512*n Bytes     512 bytes of data for 
                                        each block of the saved volume 
                                        recorded in this file where n is the 
                                        number of blocks.


Further Reference
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  o  ProDOS 8 Technical Reference

