Re: Image handling in mutt
On Mon, 11 Dec 2023, at 13:16, Greg Wooledge wrote:
> 4) File extensions are used by programs on every operating system.
Certainly on many OSes, but not all.
They're not present on native RISC OS systems (as in ex-Acorn micros).
Filetype data IS stored, but it is in files' metadata.
There's no concept of filetype in file systems used for the MVS side
of z/OS systems. (These days there's also Unix/Linux environments
& of course they do have more familiar file naming structures.)
By convention collections of separate files might all be kept in a set
very vaguely analagous to a directory - though with no parent
directory nor child sub-directories), known as a "PDS". The name
of a PDS is fairly arbitrary (subject to installation conventions &
security restrictions) & the names of files within ("members") also
have no real meaning unless an application chooses to interpret
their names in some special way.
One refers to a PDS as a whole by its name, eg "MY.SAMPLE.PDS"
& to a member within it, eg the file named "FRED", as
"MY.SAMPLE.PDS(FRED)".
While there are conventions for names of these PDSes, there's no
requirement that every file within, say "MY.SAMPLE.ASM" would
contain assembler source. Often only some of the files would do
with others containing notes etc.
If a PDS's name looks like it might contain binary executables AND
it is actually used in a place where that would be expected, then you
can infer that it does do; you wouldn't find plain text notes, sample
data etc alongside the executables (because other characteristics
of those file sets allow them only to hold executables).
You cannot tell from a file's name whether it's held on disk or
(virtual) tape or real tape, nor which device it's currently on.
--
Jeremy Nicoll - my opinions are my own.
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