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First Game: help
« Thread started on: Jul 21st, 2011, 6:40pm »
First of all kudos to Richard for BB4W!
I've just completed coding my first game on the demo version, a SimCity "clone". I have a couple of questions:
1) Is the available memory for the demo version the same as for an original BBC Micro? My game just fits into the max memory I could grab (HIMEM = PAGE + 12288). Just wondering if it would have worked on my old machine.
2) Like I said I just fit it into memory, so I assumed I must have been reaching the limits of what the BBC could do, until I saw that Superior Software made a version of Sim City for the BBC. Here it is:
And here's some screenshots from my game:
Now I know this isn't a simple question but how are they able to get so much more complexity into the game and still fit it into memory?
If anyone has some source code to share of games that would have run on the original BBC machine or anything else like that that would educate me I'd love to see it
Is the available memory for the demo version the same as for an original BBC Micro?
On the BBC Micro the available memory depended on the screen MODE (because the RAM was shared between the program/data and the screen). In the highest-resolution graphics modes (0, 1, 2) the screen occupied 20 Kbytes and the OS workspace was about 4 Kbytes, leaving about 8 Kbytes available for the BASIC program, data etc. on a Model B.
However on the BBC Micro more memory could be made available by using a lower-resolution graphics mode. MODEs 4 and 5 needed 10 Kbytes for the screen, leaving about 18 Kbytes for BASIC which is more than is available with the trial version of BB4W.
Later: Having looked at the YouTube video, the game appears to occupy only a small part of the screen. This is probably a way of making more memory available.
(Peter went on to work for the BBC; I wonder if he and Richard ever met?)
I think I remember Peter saying, in an interview, that SimCity was the conversion he was most proud of due to the significant challenges he faced given the BBC's limited memory.
For me, the game Exile was the most amazing piece of BBC programming. I still play it, occasionally.
You might find this discussion by Peter Scott (who authored the BBC Micro version of SimCity) to be of some interest
He says that he had 25K of memory available, which I assume must include the OS workspace, so that implies only 7K for the graphics screen! In a 4-colour mode that would correspond to only about 192 x 150 pixels (roughly 0.6 of the screen width and height) explaining why the display seems so small.
Richard.
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donpost Guest
Re: First Game: help
« Reply #4 on: Jul 22nd, 2011, 4:43pm »
Thanks for the responses.
I had a copy of Exile (or should I say my father did, I'm only 27), and thinking back yes thats very impressive. The game was huge. Never really got anywhere on it as I was too young really.
I think I was most impressed by Elite which I also had. A 3D environment on the BBC was outstanding.
If I remember right both of those games came with a novella. You don't see that nowdays!
I had a copy of Exile (or should I say my father did, I'm only 27), and thinking back yes thats very impressive. The game was huge.
I remember thinking it a near-miracle of BBC programming. I'd bet that many programming-minded BBC users puzzled for years over how Exile's huge map could've been squeezed into the available memory; of course, it turned out that the map was procedurally generated "on the fly" using some clever (and fast) essentially-random process. IIRC, co-author Peter Irving said, in an interview, that the map generator only occupied a few bytes of RAM.
I think I was most impressed by Elite which I also had. A 3D environment on the BBC was outstanding.
Yes, great game (I still play the emulated and enhanced BBC Master version from time to time), and we've been waiting some 14 years for Elite IV. Not holding my breath, though.
My first reaction upon loading Elite for the first time in 1987 (from tape cassette) was "Woah! That's a fast line-plotting routine!".
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