It is a programming convention (i.e. copied code), not part of ProDOS.
ProDOS 8 Technical Reference Manual
5.4 Programming Conventions
The standard Apple II "Air-raid" bell has been replaced with a gentler
tone. Use it to give users some aural feedback that they are using a
ProDOS program. The code for it follows.
And the code indeed follows.
[The following is written under the assumption it's done in Assembly. For BASIC it works rather different, but doable]
I write programs in assembly language using HGR mode. For a fluid display, I use the double buffering technique.
I assume by alternate use of Page 1 ($2000) and Page 2 ($4000), right?
Is it possible to use this technique in DHGR (double ...
but I don't know how to convert the set of hex digits the user inputs into memory into the format required for the FAC
I have a strong feeling that this is not about hex, but binary integers, 16 bit or more.
I know about FRMNUM ($DD67) and PRNTFAC ($ED2E), but I can't find the subroutine that Applesoft uses to take a decimal number and convert it to the ...
In reference to the comment "Any idea how the IIGS implements those Disk II motor detectors?"
There's this Technical Note #68: Tips for I/O Expansion Slot Card Design.
On the Apple IIGS, the Mega II select signal (/M2SEL) is used as the
enable to the slower, 1 MHz side of the system. It goes active (low)
whenever the 1 MHz side of RAM or ...
From the Apple IIgs Hardware Reference, Second Edition, pages 22-24:
Figure 2-6 - Speed register at SC036
Table 2-2 - Bits set in the Speed register
Description Disk II motor-on address detectors: To retain Apple II
peripheral compatibility, the motor-on detectors change the system
speed to 1.024 MHz whenever a Disk II motor-on ...