Disk functions

General discussions related to the Altair 8800 Clone

Disk functions

Postby jrdurgan » July 31st, 2018, 3:11 pm

Hello All,

I have several questions about disk functions. I am getting used to using virtual floppy drives. the 0,1,2 threw me for a short time. I am used to A, B, and c. Oh Well. I understand that there are three disks already downloaded to the clone. If I want to run a program on one of these disks, it has to be mounted. If I want extended basic version 5, I set the switches to access the bootloader from the Prom, and press the "Run" Switch. Basic loads. If I write a basic program, and want to save it to a data disk rather than on the program disk in drive 0, How do I do that. There are no blank disks. Can I create a blank data disk? Does it have to be Formatted? If I do create a blank data disk, I have to download it from the pc to the clone. Do I get to decide which drive it will overwrite. Do I need to save what is already on that drive back to the PC. I would experiment, but I am leery of erasing something. Now all this gets simple if when I do a disk function I get prompted for where I want it to go etc. I would appreciate the benefit of all the experience represented by the users of this forum.

J Durgan
Posts: 11
Joined: July 24th, 2018, 12:00 pm

Re: Disk functions

Postby jrdurgan » August 1st, 2018, 1:27 pm

I watched all the videos and read all the books and manuals. I think I have a handle on disk functions now.

John D
Posts: 11
Joined: July 24th, 2018, 12:00 pm

Re: Disk functions

Postby AltairClone » August 1st, 2018, 1:35 pm

The Altair floppy hardware and Altair software (Disk BASIC and Altair DOS) reference the drives by number (e.g., 0, 1, 2). When running CP/M, those same drives are referred to as A, B, and C.

As shipped, CP/M, Altair DOS, and Disk BASIC are typically loaded in the drives. These images and many others are available on the support page. If you downloaded the support package, the disk images are also in the folder hierarchy on your PC. You can easily upload a disk image whenever you need using the configuration monitor on the Clone. It only takes about 40 seconds to transfer a disk image, so don't worry too much about messing up a disk image on the Clone.

Altair disk BASIC and Altair DOS share the same disk layout and file format. CP/M uses a totally different format that is not compatible with Altair Disk BASIC and vice-versa.

If you have Disk BASIC in drive zero and boot it, then you can run the DSKINI command in BASIC to initialize the disk in drive 1 or drive 2. Unfortunately, the process takes about ten minutes (ah, the good old days).

Or... you can boot CP/M and run AFORMAT (not "FORMAT") to format drive B and/or C. AFORMAT runs in about one minute instead of ten and generates a blank disk that is compatible with Disk BASIC. AFORMAT is on the buffered CP/M disk image (CP/M 2.2b) or you can use PCGET to transfer the executable onto the CP/M disk image already on the Clone. Here's a link to AFORMAT.COM: http://altairclone.com/downloads/cpm/CP ... FORMAT.COM

Or... you can use the configuration monitor in the Clone to load a different disk BASIC image into drive 1 that has just a few files on it (e.g.,Disk Basic v300-5-F.dsk), then delete each file using the KILL command in BASIC.

With any of these techniques, you can use the configuration monitor to save the blank BASIC disk image back to your PC for future use.

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