[Coco] Updated BASIC possible, was Reading keyboard input without basic

Dave Philipsen dave at davebiz.com
Wed Feb 10 13:53:09 EST 2016

Barry, I think you meant to say, "I wouldn't be quite so sure...." And 
that's the point I was getting at.  It would be good practice to use the 
indirect jump just in case.  Personally, I was running a custom ROM back 
in the mid 80s not only in my CoCo I but also in my CoCo III.  I don't 
think I ever disturbed anything in the area of the keyboard routines but 
there are other people out there who have made changes that could be 


On 2/10/2016 9:50 AM, Barry Nelson wrote:
>   Since this CoCo Flash cartridge I am writing software for would allow a CoCo 3 to map flash rom from $8000 to $FFFF I would be quite so sure that no one will create an updated BASIC.
>> Arthur Flexser flexser at fiu.edu
>> Wed Feb 10 08:06:56 EST 2016
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>> The two most basic (no pun intended) ROM routines in Color Basic for
>> getting keyboard input are called by JSRs to $A1C1 or $A1B1.  In both
>> cases, the character that is input from the keyboard is returned in the A
>> register.  The difference between the two is that the $A1C1 routine returns
>> zero until a key is pressed, so a call to that is generally embedded in a
>> loop that is exited when a nonzero value is returned.  The one at $A1B1
>> blinks the cursor and waits until a character is entered.  (This is from
>> memory, no guarantees.)  The one at $A1C1 also has a documented vector and
>> so may also be called by JSR [$A000] if memory serves me correctly.  (Or
>> maybe it's $A002, too lazy to look it up.)  But there's no particular
>> advantage to using that, since we now know that there will be no future
>> Basic version where a direct call to the routine won't work because the
>> entry point has changed.
>> Art

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