<Subject corrected so readers can link this response to the original
question....>

On 3 Jun 2003, at 18:41, Chris Ryan wrote:

> Huynh Minh Huong asked , " What does "System Resources" on the "Performance
> Tab" of System Properties mean? ."
>
> That is the percentage of RAM available at any point in time on your
> computer. The percentage amount varies with the number of running programs.

  That is not correct.  The amount of available resources will not increase
if you install more RAM.

  "Resources" are Windows memory objects:  fonts, icons, mouse pointers,
windows(!), text boxes, check boxes and so on.  "System resources" are
resources that are currently loaded into memory and available for running
programs to use.

  The 16-bit versions of Windows took two shortcuts in their handling of
resources to maximize performance:

1.  Each loaded resource was referred to by a 16-bit "handle", which was
actually an address within a single 64K memory block used by the entire
system.

2.  It was left up to each running application to indicate when it no longer
needed to use a resource; when no application needed it, it could be
discarded and the space in the memory block used for a different resource.

  The consequence of #1 was that ask machines added more RAM, the system
resource area couldn't grow past 64K.  Windows 95/98/98SE/ME put different
types of resources into different memory blocks, which helps stave off the
problem somewhat.
  [The "System Resources Free Percentage" actually approximates how much of
these memory blocks, other than the parts used by Windows itself, remains
available.  It applies only to these blocks, and not to RAM in general.]

  The consequence of #2 is that if an application requests a resource (which
might already be in the resource area), and dies without releasing it
(either due to a bug, or a crash), that resource can NEVER be freed and the
space re-used, until the next reboot.  This is a "resource leak"; the amount
of available resources gradually dwindles to where applications cannot run.

  Windows NT/2K/XP handle resources differently, and so neither problem
manifests when those OSes are used.

David Gillett

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