!PackDisc 0.11

This program can potentially increase the free space on any FileCore based filing system. This free space which is created comes from the wasted space in shared fragments. !PackDisc rearranges which files share fragments with each other in such a way as to minimise the remaining wasted space.

PackDisc is ideal on directories which have constant contents and several small files, for example application directories, as the small files can be rearranged more effectively and the space saved will remain saved. It may also be useful for PD libraries or magazine discs or anyone else who wants to use every last sector on a floppy - it can usually save at least a couple of KB from a typical floppy. I saved 11K on a copy of the RISC OS 3 App1 disc. On my whole hard drive I saved about 10MB. [historical note - at the time that was written, a hard drive was typically less than 500MB]

The whole of the re-arrangement is done using high-level filing system calls to minimise the risk of corrupting discs. However, the FileCore bug which can corrupt nearly-full discs *could* rear its ugly head. I have not had any problems with the current version. An early development version *did* cause a corruption of a couple of very large files but these are handled differently now so the corruption should not occur.

Shortcomings of this version include:

• Single tasking (although it can be run in a taskwindow). Options (ie the display output level and names of temp directories) are changed by editing a line in the program code rather than from a front end.
• Needs a fair amount of free disc space to operate in.
• Uses far too many file operations. This makes it rather slow. A version using lower level operations would be able to go a lot faster.
• Will not work properly if any other program is accessing the disc at the same time (or rather writing to it).
• Does not cope gracefully with errors. The user must replace files which are stuck in its temp directory. Having said that, errors do not occur in my experience unless another program accesses the disc at the same time or there was too little free disc space.
• Cannot check potential savings without first doing it. This makes for lots of tedious copying which may not free any space.
• Can cause the free space map to become more fragmented during the course of normal operation. This can be partially alleviated by a *Compact, which PackDisc does automatically if the map becomes very fragmented.
• Is slowed down considerably by a very fragmented free space map. This and the one above do not work together very well...
• The optimisation algorithm is not perfect and sometimes gives sub-optimal arrangements. Indeed I have seen negative savings occasionally.
• Will not work correctly on a disc with 2GB or more of free space.

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