Does anybody remember which PEEK to use to check whether the computer has been booted with CTRL pressed down or not? Thanks in advance.

You can't check that with a PEEK.
Most of the time you need CTRL because you need the extra memory. In basic, just use the FREE(0) function to see if it's enough. If not, someone must have forgotten to press CTRL.
You *can* check with a PEEK how many drives are connected. If it's only 1, CTRL was pressed. However, when using harddisks, this won't work! You'll get 5 drives instead of 6 (using 4 partitions) and not 1... That's why I don't recommend this method. (Had to change lots of loaders for this...)

Does anybody know how you can check if the "B" drive is virtual or real?

yep, hook a routine on the 3-byte hook on $F42F. If it's called when you switch drives to display the 'set disk for drive' text, it's a virtual drive.

Then what was the PEEK to check how many drives are available? The FREE(0) method doesn't seem to be very trustworthy either, since the amount of memory in BASIC differs per system type as well, or am I mistaken? Is there in every BASIC version an equal amount of memory available?

if you need know if the "B" is availabe, just do the next:

10 on error goto 100
20 FILES"B:"
30 REM the b: is available
40 ....

100 RESUME 110
110 REM the b: isn't available

but, that generate a list... you can list a unavailable file like FILE "xxxxx.xxx" with weird chrs ... so, on ERROR handle routine, you can check if the error is a "file not found" or a "disk offline" or "bad unit name".

Without any other interfaces you can check whether the CTRL-key is pressed by peeking $FB21. If it's 1 (1 drive) CTRL was pressed during boot, 2 (2 drives) say it didn't. This only works when there's only the floppy drive connected. Any more interfaces move this up to $FB23, $FB25 or $FB27, depending on the number of interfaces. Pretty tricky things since there's no universal way of detecting that.

Thanks, that was wat I was looking for

Quote:

yep, hook a routine on the 3-byte hook on $F42F. If it's called when you switch drives to display the 'set disk for drive' text, it's a virtual drive.

I want to know it before I access a drive

Quote:

Thanks, that was wat I was looking for

OK, but please don't use it to detect whether CTRL was pressed...

I used to check if FREE(0) was > 24000. This worked in my cases.
You're right, the amount of RAM depends on the system, but not too much. For 64kB systems with diskdrive, 24000 will be sufficient, I think.

Quote:

I want to know it before I access a drive

Well, access it before @ init time. You might want to set the $F323 pointer as well though, to capture any disk errors in case there's a physical drive. Otherwise access the FDC directly, which is highly dependant on the FDC the machine uses. Alex Wulms should be able to help you with that, including detection. He did that with the format tool which uses the fastcopy 3 FDC drivers.