stardot.org.uk

And after what felt like a lot of mucking about, it builds once again! The graphics library now contains the code to draw lines with thickness and I have rebuilt the database and design app code against it. Here's what it looks like on a Master 128 in MODE 129: bcp_tracks_7.png Still did this by cal...

Very loud swear words. Not only has my latest disc image somehow become corrupt, but it must have already been corrupt before I uploaded that one the other night. More swear words. How did I manage that anyway? I have a vague memory of deleting some files and running *COMPACT ..... maybe that broke ...

What kieranhj said. Zero page is very nice but not always essential. If we look at the "main" instructions LDA , STA , AND , ORA , EOR , ADC , SBC and CMP , the "short" forms zp and zp,X execute in 3 or 4 clock cycles (2 to read the instruction, one to add X to the address and one to read the operan...

UK payphones worked fundamentally differently than US ones. In the USA, the payphone sent tones up the line to the exchange to indicate coin insertions; in the UK, the exchange sent pulses down the line to indicate funds exhaustion. Chaining together local codes was sort of possible but not always. ...

If you have messed up the stack, there is still a way back to BASIC as follows: .error BRK EQUW 60 \ custom ERR value EQUS "Your problem, meatbag" \ custom error message BRK \ end of message marker Unless you messed about with system vectors, BASIC catches BRK instructions and displays an error mess...

Yes, you can use what's normally BASIC workspace, &00-&6F as long as you don't need to drop back and forth in and out of BASIC. (Depending what your code touches, you can corrupt pointers used by BASIC and end up with the dreaded Bad program , or loss or corruption of variables; or BASIC will be abl...

Just rewritten a chunk of code, almost from scratch, because I wasn't happy with it. It's for drawing "wide" lines (either as two parallel lines in outline mode, or as rectangles otherwise). And I seem to have saved a fair amount of space; it's actually no slower to do it without pre-calculating the...

Sounds like there is a need for a smart layer which would sit as one process in the co-operative multi-tasking system, and manage several sub-processes by pre-emptive multi-tasking. It would have to be able to pull the rug from any of the processes it was managing, in order to hand back to the rest ...

Welcome to the wonderful world of CRTC register abuse! It is a lot of fun. :D Aye :) It's also interesting how manufacturers in the UK and USA adopted different approaches. We went for ULAs and fully-bitmapped screens with every pixel individually-addressable, and the processor and video ULA taking...

Back in the day, I never fully appreciated just how a screen display is put together, so I never bothered experimenting with the BBC's video system. So this must be old hat to you, but please bear with me as I'm only just discovering the joys ..... If I run 10MODE5 20VDU23,0,1,32,0;0;0; then I end u...

Well, I've already run out of memory several times; which is why the source code is split up into multiple chunks now!

And I need to export variables created during assembling from one program into the next and preserve the names, so crunching the program would just mess that process up .....

I'm doing the "minor" editing in BeebEm but I also have some scripts I've written to add and remove line numbers, so I can do major editing on the host (laptop running Ubuntu) when it's worth the bother of transferring files across. (Maybe I need to write a script to detokenise BASIC on the host.......

Backspacing during wiring works now, eventually! I don't think it helped much that my cat was sick on my handwritten notes ..... The code is a mess, though, and there's still a bit that's not quite right and will break the next addition; so I'm going to give it a bit of a tidy before posting another...

No worries, the main thing is it's uncompressed and it seems to hold the position. I guess I could pore over the UEF format specification and work out exactly what all the stuff on the front means, but I'm happy with a slightly hacky solution for now.

Brilliant! I'll try that as soon as I get home and fire up my laptop EDIT: Well, it sort of worked; except (after some playing around with the ? operator) with my version of BeebEm (0.0.13), the offset turned out to be &5C. Anyway, this worked for me: $ dd if=beebem/state.uef of=bbc_ram bs=1 skip=92...

Is there a quick and dirty way of extracting the Beeb's RAM contents from a saved state file (*.uef) with the `dd` command or similar?

Putting it another way, is the file uncompressed, and the RAM contents always at the same offset?

I would recommend avoiding anything like a BSD / MIT / ISC / Apache licence. These boil down to "Sharing is not stealing" -- anyone is allowed to take your hard work, make their own subtly-different but incompatible derivative and cage up the Source Code which you intended to be shared freely. For i...

If you're going to be writing anything "database-y" then you will have to get thoroughly familiar with the (zp),Y addressing mode. You'll need a list of the starting points in memory and lengths of each record, and two two-byte pairs in zero page to act as the pointers to your list and the record it...

And, as promised, a disc image for you to play with: bcpdemo4.ssd This jumps straight into the command mode. There are two more designs saved, that can be loaded by pressing f7 or f8. GOTO 11010 can be used to resume execution after stopping with an error. You can now use the W command to wire up co...

Ah, yes, the great compression trade-off; do you want the decompression code small and fast but the compressed code larger, or the compressed code small but the decompression code larger and slower? Every situation is different ..... Sometimes you might even need to use more than one compression sch...

Guess who just spent an hour chasing something that was her own fault all along ..... :oops: I had stored a copy of some co-ordinates in a part of the workspace I knew I was not writing to ..... we'll call it plotbuf ..... but something was overwriting it nonetheless ..... been poring over listings,...

Now we have the beginnings in place for the W ire command! Given a part and pin, it begins searching through the wiring list for a suitable destination, i.e. any pin which is connected to the same circuit node. (And so far, it doesn't do anything more than output some details to the screen: the curr...

*SIGH* Two steps forwards, one step back. Command parsing and despatching works exactly as I had hoped with command modifiers, so I have my V command! I can alter the viewport to my heart's content, and display its co-ordinates. So far, all good. Now my BASIC so far has just naïvely drawn all the c...

Sounds like you are really enjoying this; quite inspirational :) Well, I wouldn't be doing this if I wasn't enjoying the living daylights out of it :D Screenshots; probably not really of much interest to anyone except hardcore hackers, but you can see me calling the subroutines from BASIC that are ...

Here is a disc image containing a demo of what has been achieved so far. You can draw everything in the design; play at routing; and test the "M" (move) command. f7 and f8 -- load one of two slightly different designs (they're actually more different than they look ;) ) each containing R1, R2, R3, R...

Oh, yeah ..... The number of variables exported from this last chunk of assembler, which I'm already calling the app code now, is tiny compared to what came out of the libraries! This feels good

I have written some more machine code to replace parts of the BASIC test program. And I now have a clear roadmap ahead for the command interpreter. bcp_parse_cmd.png Bumping into memory limitations, so going to have to split out the assembly language source from the BASIC program that calls the mach...

One thing I always wanted to do, but never got the chance with real Beeb hardware, was a game that would supplied on cassette but include a disc installer. (The first draft of the idea would have involved mounting a small magnet inside the cassette shell, downstream of the playback head, to ensure i...

There must have been quite a few "bespoke" educational games and apps written specially, by teachers or even pupils at that school, and possibly shared with other schools. (I've known a few teachers who were married to teachers working in different schools, and/or related to teachers living and work...

On an original NMOS 6502, indirect addresses across a page boundary are broken: the high byte of the address bus is not increased after reading the low byte of an address from the last byte within a page. For instance, JMP(&4BFF) gets the low byte of the address from &4BFF, but the high byte from &4...