linux music tools It is quite possible and was done all the time in the bad

[martin McCormick]

old days of severely limited system resources that we all had
back in the eighties and early nineties or in 2015 if one is a
glutton for punishment.

	It was called overlaying and a smart programmer could
write an executable file which was built to come apart like a
piece of large furniture such that there was probably part of the
program in memory all the time plus one or more sub-parts which
were sucked in to memory while the application was doing
particular things and then another piece would be pulled in when
something else needed to be done and so forth.

	The program could have been huge and there was
theoretically only one limit and that was fitting the whole
bundle on to the disks used for installation and or the hard
drive.

	I used to write 8086 code on a Microsoft assembler when I
was learning how to crash P.C's scientifically in the eighties
and I remember there were instructions in the manuals for how to
write overlays. I never got that sophisticated but real
programmers did write exactly the kind of code being discussed
here and that's how applications that could not fit in to your
memory did, well, sort of.

	Nowadays, there is not nearly as much need to do that
sort of thing when writing applications but the idea of virtual
memory makes it happen automatically.

	If you use the "free" command on a unix system, it will
tell you that you have X amount of memory. That's your RAM.
That's the golden memory, the fast stuff that makes your system
really scream along.

	When you now pull in a big bunch of data, the operating
system puts as much as it can safely afford to do in an area of
RAM and, if there are still too many data elements, it uses swap
space on your hard drive that you hopefully have setup for
just this eventuality. This is not nearly as fast as your RAM,
but it beats crashing the program or you whole system and
programmers who write applications do not have to worry about
overlays and which parts of the executable are accessible at what
times nearly as much as they used to do.

Martin

Shlomi Fish <shlomif at shlomifish.org> wrote
> Hi Janina and everybody,
> 
> On Sat, 25 Jul 2015 16:00:12 -0400
> Janina Sajka <janina at rednote.net> wrote:
> 
> > Are you serious? The Lilypond executable alone is 4.5 megs. How's that
> > supposed to even run within the 640K confines of DOS? Let alone the
> > required libraries to compile the binary?
> >
> 
> I recall that DJGPP (see https://en.wikipedia.org/wiki/DJGPP )?s 
> executables
> could access more RAM than that using
> https://en.wikipedia.org/wiki/DOS_Protected_Mode_Interface (DPMI). So it 
> may be
> possible.