!Squash
                    =======

Squash is copyright © Acorn Computers, 1991.

!Squash is an application which compresses files using the RISC OS Squash
module. The Squash module currently compresses using a 12-bit LZW
algorithm but no guarantee is made that this will be so in the future.

To use !Squash simply double click on the !Squash icon in the relevant
directory display. This will install !Squash on the icon bar where the
!Squash icon should then appear.

Compressing a file
==================

To compress a file simply drag it to the !Squash icon on the icon bar.
A save box will then be displayed which will contain the file name, a file
icon and an OK button. The compressed file may be saved back to itself
(ie. it will replace the original) by pressing return or clicking on OK
without changing the file name. If the file name is changed or the file
icon is dragged to a directory viewer then the original file will be left
untouched.

Decompressing a file
====================

To decompress a file either double click on the compressed file or drag it
to the !Squash icon on the icon bar. Double clicking on a compressed file
will overwrite the compressed file with the decompressed file. Dragging to
the icon bar allows the decompressed file to be saved elsewhere.

Compressing and decompressing files and directories
===================================================

To compress or decompress a directory just drag the directory to the !Squash
icon on the icon bar. A save box will then be displayed which will contain
the file name, a file icon, an OK button and two toggle buttons. The toggle
buttons are used to specify whether the contents of the directory are to be
compressed or decompressed, otherwise the procedure is the same as for
compressing files.

Menu options
============ 

!Squash has one menu displayed by pressing Menu on the !Squash icon on the
icon bar. This menu contains four options:

Info:        Displays some information about the version of !Squash which is
             running.

Save Box:    Toggles the use of the save box.  The save box is switched on
             initially which results in the manner of operation described
             above.  Sometimes, if a large selection is made and dragged to
             the squash icon for example, it may not be desirable to have a
             save box for every file or directory selected.  This menu option
             can be used to turn off the save box which means that all files
             and directories will be replaced by their compressed versions.

Squash Apps: This is used to toggle the compressing of application 
             directories. This is initially off ie. application directories 
             which are found as a sub_directory of another directory are not              
             compressed. Application directories which are explicitly dragged
             to the !Squash icon will always be compressed.

Quit:        Terminates the !Squash application.

Squash utility program
======================

The !Squash directory also contains a utility called "Squash".  This utility
can be copied to the Library directory and used on the command line to 
compress files. The syntax is:

Squash <from-file> [<to-file>]

With a single file name the compressed or decompressed version of the file
replaces the original.  With a second file name the result is written to the
specified file.  Note that directories cannot be compressed using this
utility.

With both !Squash and the command line utility, if an attempt is made to
compress or decompress a zero length file or the result of a compression is
larger than the original (this can happen for very small files) then the
original file will simply be copied.  If the original file was to be
replaced by the output then the original file is left untouched.

NB. Squash prepends a header to the compressed data.  This header is of the
form:

           4-byte ID:       "SQSH"
           1-word:          length of the original, uncompressed file
           1-word:          load address of the original file
           1-word:          execution address of the original file
           1-word:          reserved (currently always 0)

Where the load and execution addresses are used to hold the file type and
the date stamp of the original file.  These are restored when the file is
decompressed.