The backed-up disks are 8" Altair Disk images formatted under CP/M. They are
bootable CP/M v2.2b disks and should contain encoded MBASIC-80 source files
as well as a working copy of Microsoft BASIC 80.
In order to read these disks, you have two options: 1) throw it into an
Altair 8800 emulator and call it a day or 2) write it to a real Altair 8"
disk using something like an FDC+ card (which can also emulate an 8" disk
drive using a 96tpi 5.25" drive). Unless you have a real Altair 8800, I'm
sure you'd prefer to go the emulation route. I don't have a lot of
experience with different Altair emulators, but I can confirm that Altair32
for Windows works very well. Note that programs that output to the data
LEDs will not function properly in an emulator, as this is a feature of
Mike Douglas' Altair 8800c front panel board and not of the original
Altair 8800 front panel by MITS.
In Altair32, first turn on the Altair using the on/off toggle switch. Then
load in the disk file to drive zero using the 'Devices -> Diskette Drive'
window. The disk boot loader is at address FF00, so toggle up the first 8
switches on the address line (A15-A8) and leave the rest down. Examine the
address by clicking down on the examine switch (the first 8 address LEDs
should then light up above the switches) and then flick the run switch. If
all goes well, a terminal window should pop up and you should have a CP/M
prompt.
CP/M is a lot like MS-DOS, but it *is* different. You can list files using
the "DIR" command. You can run Microsoft BASIC 80 by typing in "MBASIC"
and pressing enter to load the program. Know that the CP/M BIOS
automatically converts all commands at the A> prompt to uppercase, so even
though you may see lowercase-named files on the disk, they will not be
accessible via CP/M itself. You can access them from within BASIC, though.
Once in BASIC, you can get a file listing by using the "FILES" command.
To load a file, use the "LOAD" command, along with a filename surrounded
by quotes. Filenames are considered strings, so if you don't use quotes,
you'll get an error:
```
FILES
SENSESW .BAS ENTERNAM.BAS WUMPUS .BAS led .bas
Ok
LOAD SENSESW.BAS
Type mismatch
Ok
LOAD "SENSESW.BAS"
Ok (actually loaded here)
```
To save a file, use the "SAVE" command in a similar fashion. Remember that
filenames can be up to eight (8) characters long with a three (3) character
file extension. If you omit the extension, ".BAS" will be used.
```
SAVE "SENSESW
Ok (saves to SENSESW.BAS)
```
Unlike at the CP/M prompt, filenames are case-sensitive here, so be sure to
type them correctly. You do not have to add the final quote if you don't want
to.
To list the contents of a program, you can use the "LIST" command, and to
run a program, use the "RUN" command. "NEW" clears out the program area
and "CLEAR" clears out the variable area in memory. There is no clear-screen
command like there is in later BASICs on home computers designed to output
specifically to a video display.
If you are doing this on a real Altair, be sure to remove the disk before
shutting the Altair off and to not have the disk in until both the disk
drives and the Altair are powered on and in a ready state or else the disks
may have random data written to them and become corrupted. I learned this
the hard way :')
Anyway, that's about all you need to know about reading these disks! The
Microsoft BASIC-80 manual has more information on BASIC commands and such, and
there's plenty more information out there on the internet about reading and
writing disks on a real Altair.
