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After The
Installation, The Mouse Does Not Work In Windows
Verify that the mouse
works in DOS before you load Windows. Load the mouse driver in either the
CONFIG.SYS or AUTOEXEC.BAT file. For example, to load the driver for a
Microsoft-compatible mouse, use one of these two methods:
Use this command in the
CONFIG.SYS file:
DEVICE=\DOS\MOUSE.SYS
Use this command in the
AUTOEXEC.BAT file:
\DOS\MOUSE.COM
Boot to the DOS prompt
and test the mouse. Try to edit a file using EDIT.COM. If the mouse driver
loaded correctly, you should have the use of the mouse in this editor. If
the mouse still does not work, you are probably using the wrong driver for
the type of mouse you have.
Most often, a mouse
comes with a disk containing the driver file for the mouse. Try the driver
on this disk.
After you have the
mouse working in DOS, try loading Windows again.
Memory Paging
How does Windows 9x
provide virtual memory addresses to DOS and 16-bit Windows application
programs? By memory paging, which is managed by the Virtual Memory
Manager.
Look at the following
figure. In the top diagram, you can see the Windows 3.x memory model.
Application programs in Windows 3.x share the memory addresses that have
been assigned to either the physical or virtual memory of a system. For
example, in the following figure, 64 MB of memory addresses are available.
Although 16-bit programs run in conventional memory, they might store
their data in extended memory. Of the 64 MB, perhaps half of these
addresses are assigned to physical RAM stored on SIMMs or DIMMs, and the
other half of the addresses are virtual memory contained in the swap file
on the hard drive. In this case, there is only one set of memory
addresses, and all application programs must share these addresses.
As you can see in the
lower part of the previous figure, Windows 9x not only has virtual memory
stored in a swap file but also provides virtual memory addresses to
application programs. In the previous figure, you can see three sets of
virtual memory addresses. Each set can contain 0 to 4 GB of addresses,
depending on the amount of virtual memory available. The top set is being
used by two 16-bit programs. The second set of virtual addresses is being
used by a single DOS program, and a third set of addresses is being used
by a 32-bit program.
Each VM for DOS has a
set of virtual memory addresses. The 16-bit Windows programs share a
single set of virtual memory addresses, and each 32-bit program has its
own individual set of addresses.
In the previous figure,
all these virtual addresses map onto the page table, which in turn maps
onto either physical memory (RAM) or virtual memory on the hard drive
(swap file).
Obviously, not all
virtual memory addresses in Windows 9x have physical or virtual memory
assigned to them. These virtual addresses remain unassigned until an
application program uses them.
In Windows 9x, the
Virtual Memory Manager controls the page table, moving 4K pages in and out
of physical RAM. If a program requests memory that the memory manager
knows is stored in the swap file, the manager generates a page fault,
which causes the manager to go to the drive to return the data from the
swap file to RAM. This action is called a page-in. If RAM is full, the
manager takes a page and moves it to the swap file, which is called a
page-out. If RAM is full much of the time, the Virtual Memory Manager
might spend excessive time moving pages in and out of RAM, which can cause
excessive hard drive use and a decrease in overall system performance and
can even cause a system lockup or applications to fail. This situation is
sometimes called disk thrashing and can cause premature hard drive
failure. Symptoms of excessive memory paging are:
Very high CPU use
Very slow system
response
Constant hard drive use
The solution is to
leave fewer application programs open at the same time or to install more
RAM.
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