STEP-6.2 changes:

If a file to be read is not found in the current directory, we look
for it in one of the directories listed in the environment variable
STEP_INPUTS.  All words for reading files will follow this convention.
Also, all words for reading buffers will first check for a .gz version
of the filename (in all of these places).


New keys:

We introduce the concept of the "base" directory, which is a directory
that contains a set of experiment subdirectories.  The base directory
can be changed or listed using the "d" key:

        d Directory:

A full path name (starting with a /) must be given to change the base
directory.  Simply hitting return gives a listing of subdirectories of
the base directory.  Entering a path name containing an "*" gives a
listing of matching files within the base directory.


The current or active directory will be called the "experiment"
directory, and can be changed or listed using the "e" key:

        e Experiment:

A path name containing an "*" gives a listing of matching files within
the experiment directory.  Simply hitting return is equivalent to
entering "*.exp".  Whenever the experiment directory is changed to
"dirname", the default for the "l" key (load) is changed to
"dirname.exp".


The rest of the key functions are unchanged.  They all save or load
files relative to the current experiment directory:

        l Load.file
        p Put.pattern
        g Get.pattern
        r Read.colormap
        w Write.colormap

but we add deferred words

        before-get      after-get       before-put      after-put

that operate before and after the "get" and "put" keys, to allow for
special operations that are needed whenever patterns are saved or
loaded.  We also let the experiment set default patterns for "put" and
"get" using "set-get-default" and "set-put-default".


Other changes:

We now have the software check memory size whenever you execute
"new-experiment", so that 16Meg machines will operate correctly
automatically.