HELP POP_FILE_VERSIONS                              Mark Rubinstein, May 1 1985

    <integer> -> pop_file_versions

This variable controls the number of backup copies of files POPLOG keeps.  Its
default value on UNIX machines is 2, meaning that POPLOG maintains the most
recent copy of a file and its previous version (if there was one).  Its
default value on VMS machines is FALSE, meaning that no attempt is made by the
POPLOG system to limit the number of backup copies created.

If you are using a UNIX machine and want POPLOG to keep the last 3 copies of
every file as well as the most recent copy then you should assign 4 to
POP_FILE_VERSIONS, i.e:

    4 -> pop_file_versions;

If this is put in your INIT.P file (see HELP *INITIAL) then POP_FILE_VERSIONS
will be set every time you use POPLOG.

--- Backup Copies (VMS) ----------------------------------------------------

On VMS file names have a version field. That is, file names always have the
form

    <name>.<extension>;<version>

for example

    'foo.p;3'

The most recent copy of the file is the one with the highest version number -
there is no need to specify the number if you want to access the most recent
version.

Previous versions of the file have the same name and extension as the current
version but a lower version number; the latest backup copy has a version
number one less than that of the current version, and so on.

--- Backup Copies (UNIX) ---------------------------------------------------

On UNIX file names are not divided into fields in the same way as on VMS;
however it is convenient to think of any characters up to the last period in a
name as being the name, and any characters after the last period as being the
extension.

UNIX does not normally create backup copies of files and has no notion of
version numbers.  POPLOG however provides backup copies by attaching minus
signs ('-') to the file specification (shortening the name first if necessary
to keep the file name within the length limit).   For example, if you have a
file called 'foo.p' which has two backup copies (POP_FILE_VERSIONS would need
to be set to at least 3) then the most recent backup copy is called 'foo.p-'
and the version before that 'foo.p--'.

See also
    HELP * VEDVERSIONS - for limiting the number of backup copies in VMS
    HELP * PURGE       - for details of deleting files in VED
