Numeric Characters

[molecularr]

Hello,

 

I'm researching different lettering and numeral designs used in Atari 2600 games, and I've run into a problem. Basically, the problem is that, whereas for most games I can "print" the text sprites by rendering the binary in some textual form (e.g., X's and .'s), I've come across a few games where that doesn't work.

 

As I understand it, the 2600 lacks any implementation of ASCII, so when a particular character is needed, it's shape has to be stored directly in the game ROM, right?

 

But for Wizard of Wor at least (and several others I've forgotten off the top of my head), this does not appear to be the case. When I print out its binary, I see the other sprites, but no text or numbers.

 

Does anyone know what's going on here? I've seen conflicting information about whether Wizard of Wor uses the RAM+ chip, but if it does, is it possible that there's a small character set stored there?

 

I really have only the most basic understanding of programming for this console, so it's likely that I'm missing something obvious.

 

Any suggestions?

[Thomas Jentzsch]

As I understand it, the 2600 lacks any implementation of ASCII, so when a particular character is needed, it's shape has to be stored directly in the game ROM, right?

Right.

 

But for Wizard of Wor at least (and several others I've forgotten off the top of my head), this does not appear to be the case. When I print out its binary, I see the other sprites, but no text or numbers.

That's because the data can be stored in several ways, whatever suits the programmer best.

 

In WoW, the graphics are stored interleaved (10 byte distance) starting at offset $f0a. Unusual, but probably not the only game doing it like that.

[molecularr]

Thanks. That makes sense to me. So here's another, even more basic question: How do I find $f0a? I can't read/convert binary in my head, so I've just been printing each byte with an ascending decimal. Decimal f0a would be 3850, but upon looking there, I didn't see a character. There's something there, but I can't tell what it is. Am I looking in the right place?

[Cybergoth]

I think the key word TJ used in his explanation was that the data is stored "interleaved".

[molecularr]

Oh, right. I get it now. For some reason I was thinking that the whole character would be "leaved" and interwoven with other stuff, but that's obviously wrong since I would have already seen that. Duh.

 

Thanks!!

[supercat]

Different games use different methods of storing shape data. Some are easy to find. Some require a bit of work. Some would be impossible to find without a detailed understanding of 6502 code (the victory message from Toyshop Trouble, for example--can anyone tell me how that's stored without looking at the source code? Feel free to look at object code, trace logs, etc. in making the determination.)