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Section 4 - Chapter 2
Using AlphaVUE, edit your TEST.INI file. Add the new device name to your device
table; that is, add the three-character device name to the DEVTBL command line. This
defines the new device name, and allows input and output to take place through the
new device driver. Disk devices are always sharable devices, so do not use a /
anywhere before them on the DEVTBL line. If you cannot fit the new device names all
on one line, use more than one DEVTBL command.
You must include both the device name and all valid unit numbers in the DEVTBL
command line. Thus, if you are adding a double sided/double density AMS-format
floppy driver to your computer and want to be able to reference both drives 0 and 1, you
must add the device codes DDA0 and DDA1 to the DEVTBL command line.
To allow the computer to write information on the new device, you must define a bitmap
for the new device. A bitmap is the method by which the computer allocates space on
the device. To add a new bitmap, place a BITMAP command for the new device
immediately after any other BITMAP commands. The BITMAP command requires you
to specify the device name.
If you are not using paged bitmaps, you have to specify the bitmap size, and the units
(drives) to which this bitmap will be applied. The bitmap size depends on the particular
device you are defining. If you are working with a floppy disk drive, the FIXFLP program
will tell you the bitmap size. For disk devices, the FIX420 program will tell you the
bitmap size. If you have a self-configuring disk, you don’t need to know the bitmap size.
See your System Operator’s Guide to the System Initialization Command File for more
information about bitmaps.
Each BITMAP command actually defines a buffer in system memory which is used for
reading and writing the bitmap to and from the device. This bitmap buffer may be
shared by multiple units of the same device, resulting in a saving of system memory. In
exchange for this saving, however, I/O must be done more frequently to the device to
update the buffer than if the bitmap buffers were not shared.
You may wish to include the driver program in your system memory area for faster
response while working with the new device. To do this, insert the command:
SYSTEM xxx.DVR[1,6]
where xxx.DVR is the driver name, into the system initialization command file just above
the final SYSTEM command line. In almost all cases, this is not really necessary, as the
computer will fetch the driver from the disk each time it is needed if it is not already in
memory, and will load it into the memory partition of the user who is requesting access
to that device.
Do not include the driver for your System Device in system memory—since that driver
was MONGENed into your monitor, it is always in system memory anyway, and adding
it by using the SYSTEM command just takes up unneccessary space.
System Operator’s Guide, Rev. 00