Using Powr-Disk, CDOS, and Disk-Power Operating Systems on the Model 100.
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By John Shadel [73537,775]

Now that there are many Disk operating systems available for the Model 100, it 
seems logical to be able to use any number of them to achieve the desired 
results using the Model 100. If you are like myself, and more than one Disk 
Operating system, you may like features from some depending on the design of 
the DOS, as well as the applications which are found here on the SIG. Some of 
the systems have greater support due to the fact that they have been out for 
some time, while still others are very new. Problems can result when trying to 
use more than one DOS due to the use of certain areas of memory by different 
programs. The Hook table, starting at >FADA and continuing through >FB48 seems 
to be the major area of concern. Also in the case of Disk-Power by Ultrasoft 
Innovations, the DOS cannot be removed from the RAM of the Model 100 except by 
causing a Cold Start, or renaming the program (not possible in Basic). In the 
case of Power-Disk by Acrotix, and CDOS by PCSG, the DOS can be removed through
the command LFILES OFF, which resets the hook table in both programs. Power-
Disk however does not clear high memory. 

CDOS and Power-Disk are designed somewhat differently than Disk-Power, in that 
they reside in high memory, and can be removed when desired. Disk-Power on the 
other hand is designed to permanently reside in the memory normally used by 
Text files and Basic Programs, and has been designed to not be recognized by 
the Basic Interpreter by commands which deal with the RAM (such as KILL,RENAME 
etc.). The initial settings used by Disk-Power in the Hook table are lost when 
the other DOS's are run, and Disk-Power does provide a way to reset them. The 
only method available for running Disk-Power again was to reload it using the 
supplied programs included on the diskette (which requires the RAM to be clear 
of all programs except for the loader programs.)

 Disk-Power does not allow itself to be cleared from memory, as the authors 
felt that the DOS should be permanently stored in memory. This is a good 
feature because it is impossable to accidently erase the DOS and have to go 
through the pain of loading FLOPPY.CO, but becomes a problem when Powr-Disk or 
CDOS have been run and then are disabled, and you wish to run Disk-Power again.
Because the hook table has not been set back to way Disk-Power initially set 
it, a cold start will result. 

In order to remedy this situation, I have written MLOPSY.BA. This program 
allows you to choose what operating system you which to run, and then does 
various error checking to be sure that the option you have chosen can be run. 
It has only been implemented for Disk-Power, Power-Disk, and CDOS since these 
are the DOS's which I own, but probably can be modified to work with TS-DOS 
also. In this way, I have been able to run Power-Disk, Disk-Power, and CDOS 
without any cold starts or other problems. The program erases Power-Disk from 
low memory when it is installed to save on space, and restores it when another 
DOS is loaded. Be careful to not clear high memory before it is restored, or 
you will have to get it back from your backup copy. CDOS already clears the 
copy in low-memory out, and Disk-Power as mentioned above does not allow itself
to be removed. Error checking is done for missing DOS's, and appropriate 
messages are displayed to aid in using the program. If you have any questions, 
please E-mail me. My number is [73537,775], and I am usually on the system 
every week or so. Please Enjoy and feel free to modify or use this program in 
any way.