[Coco] Re: Newbie help: Barden Bubble w/ Portal-9

[jimcox at miba51.com]

On Tue, 27 Jan 2004 12:56:48 -0600
  Roger Taylor <rtaylor at bayou.com> wrote:
>At 09:39 AM 1/27/2004 -0500, you wrote:
>>Theodore (Alex) Evans wrote:
>>
>>>On Jan 26, 2004, at 7:39 PM, <jimcox at miba51.com> wrote:
>>>
>>>>Roger:
>>>>
>>>>I just assumed that since the code was listed in Bardens 
>>>>book that it would run if EDTASM+ plus were installed in 
>>>>the CoCo, and so I thought Portal-9 would do the same.
>>>>Jim
>>>
>>>I personally can confirm from experience that under 
>>>EDTASM+ the code runs exactly as published.  Of course as 
>>>pointed out, if you want to save it as a binary, you need 
>>>to supply a load address when you load it off either 
>>>cassette or disk.
>>
>>I guess I should point out that one of the features of 
>>EDTASM+ is in memory assembly in addition to assembly to 
>>disk. The IM switch is intended for ZBUG use which 
>>permits running the ml program from within EDTASM+; among 
>>other things.
>>
>>When EDTASM+ does an in memory assembly, it automatically 
>>places the code in a safe location so that EDTASM+ and 
>>system code is not over written.
>
>
>And there's another issue with his examples; they're not 
>all meant to be loaded and executed.  Some are to examine 
>the listing to see what the opcodes are, etc.  To 
>generate a listing with Portal-9, type in "-l" in the 
>'assembler options' field.  To see the symbols list, use 
>"-s".  You can use "-l -s" to do both.  "-sa" lists all 
>symbols, including local labels.
>
>If you still want to be able to LOADM and EXEC an example 
>from Barden's book that is missing an ORG statement, just 
>add something like ORG 16384 for the 1st line of the 
>source before you build.
>
>Here's what's happening:
>
>In the left panel under the "assemble file as, type:" 
>field, choosing "multi-record" tells the assembler to 
>create a program file that BASIC can LOADM.  Actually, 
>"single-record" can do the same, but you lose the ability 
>to embed uninitialized variables/tables in your program. 
> That's a whole other subject.  Make a habit of choosing 
>"multi-record" any time you are building a program or 
>game that is meant to be LOADMed from BASIC.
>
>In your source code, the ORG psuedo op tells the 
>assembler to create a program file that BASIC knows WHERE 
>to LOADM.
>
>No ORG at all more-or-less tells BASIC to LOADM your 
>program at address 0, which will almost always crash your 
>CoCo since that is a system area.
>
>If you just absolutely want to assemble your program to 
>have an origin of 0, it might run correctly if you've 
>stuck to the position-independent rules of coding, so 
>doing something like a LOADM "GAME", 16384  would cause 
>your game to load at address 16384.  The value of 16384 
>is added to the value of 0 (the origin you specified, or 
>didn't specify).  The LOADM "program",offset  syntax 
>always adds "offset" to any ORG (origins) of your 
>program.
>
>Oh, and a multi-record file can have multiple origins. 
> That's the whole idea, to let the loader (LOADM) have 
>the ability to load around memory areas, or even jump to 
>new addresses during the load process.  You can actually 
>create a mini-movie that plays on the 32x16 VDG screen if 
>you build a large program that keeps loading 512 bytes of 
>data at address 1024 (the screen) over and over until the 
>end of the file.  I confirmed this little gig many years 
>ago during my hand-assembly days.  :)
>
>I hope this doesn't add confusion to what is really a 
>very simple concept.
>

Roger:

This actually clears up a few things for me.  I know this 
is documented some place and I will eventually find it, 
but what is the specific address range we should use with 
ORG in both Portal-9 and a real CoCo?

Jim