The Apple II has two popular operating systems, DOS 3.3 and ProDOS. If you've ever been trapped between them, you'll appreciate this utility—it adds new commands to let you read and write DOS 3.3 files from within ProDOS, and move ProDOS files to DOS 3.3.
Most Apple users have two stacks of disks—one stack ProDOS and one stack DOS 3.3. That's not a problem until you want to use a program in one operating system that's written for the other one. Some people convert all of their 3.3 files to ProDOS format with a conversion utility. For the user with a large number of DOS 3.3 disks, this can be a trying experience.
"Double-Duty DOS" offers a different approach—it lets you view DOS 3.3 catalogs and load and save BASIC and machine language programs, all from within ProDOS.
Since this program is a ProDOS utility, be sure to boot with ProDOS when you are ready to type it in. The program must be entered with the Apple version of the "MLX" machine language entry program, which can be found elsewhere in this issue. When MLX asks for a starting and ending address, respond with these values:
STARTING ADDRESS? 3000 ENDING ADDRESS? 3A17
Type in the program. Before leaving MLX, be sure to save a copy to disk.
A Door To The Old World
Let's give Double-Duty DOS a test drive. Boot up in ProDOS and BRUN the program. In addition to the normal commands that are available in ProDOS, you have several new ones designed especially for accessing DOS 3.3 disks.
Here is a list of the new commands:
DCAT,Ss, Dd DLOAD filename, Amemloc, Ss, Dd DSAVE filename, Ss, Dd DSAVE filename, A$hhhh, L$hhhh, Ss, Dd
Parameters in italics are optional. The s stands for slot number, and d is for drive number. Place a DOS 3.3 disk in the drive and type DCAT. You'll see a list of all the files on the disk. You can then load any of these DOS 3.3 files using the DLOAD command, and save them to a ProDOS disk with the standard SAVE or BSAVE commands.
In the DLOAD command, the load address can be specified as a decimal or hexadecimal number. Precede hexadecimal values with a $. For example, DLOAD TEST, S6, D0, A$900 loads a DOS 3.3 binary file named TEST into location $900 from slot 6, drive 0.
You can also move files from ProDOS disks to DOS 3.3 disks. Simply load a program from a ProDOS disk and save it to a DOS 3.3 disk with the DSAVE command. Because of a limitation in DOS 3.3, you cannot save programs larger than 122 sectors (30K).
While the DLOAD command mimics both the normal LOAD command and the BLOAD commands, DSAVE has two different syntaxes. The first form listed above is for use with BASIC files, similar to SAVE. The second form is for binary files, and is used like the BSAVE command. Note that in the second form, the address and length parameters must both be specified in hexadecimal (preceded with a $).
Double-Duty DOS comes in handy any time you need to move from one world to another.