Re: Wall Defence game for Apple II

["winston19842005@yahoo.com" <winston19842005@yahoo.com>]

On Apr 24, 3:51 pm, mmphosis <markwst...@yahoo.com> wrote:
> On Apr 24, 11:49 am, winston19842005 <bjjlya...@NOSPAMbellsouth.net>
> wrote:
>
>
>
> > On 4/24/10 2:09 PM, in article
> > _vCdnZJ7Qblbrk7WnZ2dnUVZ_gSdn...@giganews.com, "Michael J. Mahon"
>
> > <mjma...@aol.com> wrote:
> > > eriknoc wrote:
> > >> I like the idea of porting games to the Apple II series.  Nice work,
> > >> except it's very difficult to aim & control because he keeps moving,
> > >> and fast, and having to press another direction or key to make him
> > >> stop takes some of the fun away from playing the game IMHO.  Is this
> > >> how it works on ports to all the other systems?  I would have made it
> > >> to where letting go of a key or direction would make you stop and
> > >> holding it down would make you go.  That would make more sense to me
> > >> anyways.
>
> > > That kind of control can be implemented on the Apple //e and later
> > > machines, but the ][ and ][+, like many other computers of the day,
> > > cannot sense when a key is released.
>
> > I'm trying to get my head around this statement...
> > Why not? What does the keyboard return after you stop pressing a key?
> > Does it not return a special value for "no key"?
>
> > Signed,
>
> > Confused?
>
> I think that Michael J. Mahon is referring to this:
>
> STROBE =   $C010 ;clear bit 7 of keyboard data ($C000)
> If read, it also provides an "any key down" flag in bit 7, with
> the keycode in the remaining bits. (These features only apply to
> the IIe and later machines.)
>
> http://home.swbell.net/rubywand/csa2pfaq.html#004
>
> Althought, this note doesn't mention "key up" only "any key down."
> Can you really detect "key up" on Apple IIe and later models?  And if
> you can, how is this done?  Documentation?

Ok, I thought you'd just keep history of what was pressed before and
look for a change.

I'm a TI-er, and we use CALL KEY (or usually the assembly KSCAN
routine, which it more or less directly calls), and it returns two
values. One is the ASCII key-code of the key currently held down (-1
if none), the 2nd returns a 0 if no key pressed, 1 for key pressed and
-1 for key held down. Is that similar to the "any key down" thing, or
am I just not following?