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Now, that's kind of handy!

It did set me thinking briefly about a complete adventure creation system, starting out in BASIC and gradually moving over to assembler until most of it is just PROCs and FNs calling machine code routines that implement drop-in replacements for the original BASIC .....

I've just finished porting The BBC Native Buildable Version of BCP back to BeebAsm; and apart from a bit of bother with ORG statements, that I can take care of permanently with another quick bit of host-side scripting or just put up with having to do by hand, it just worked. I am now fully satisfied...

There's an explanation of the BCP build process at the following link:

https://github.com/JulieMontoya/BCP_des ... ld-Process

How did Acorn ATOM BASIC handle its own, simpler "labels"?

I noticed while in the course of probing into how BASIC stores its programs and variables that line numbers are stored "backwards" to how the 6502 usually stores multi-byte values. If you are sure you are comparing unsigned numbers, you can CMP the high byte first, but you don't have to store it fir...

Ah, yes, "copy prevention" schemes that actually did nothing of the sort. The protection code cannot tell whether it is running from the original cassette or a verbatim (perhaps bandpass-filtered) audio copy; and if you start by dangling a 62256 off the address and data buses, you can just get your ...

The video system on the BBC Micro (which takes it in turns with the CPU to access RAM, in such a way as neither one even knows the other one is there) generates all its own addresses. Scrolling is achieved by starting drawing the screen from a different place in memory (so a line from lower down the...

MkSrc has also been useful a couple of times when I've foolishly overwritten my source code. Source code "KBD" saves object code "KBD", OOPS! Ouch! I feel your pain. If Dave Cutler had brought transparent file versioning -- surely the real killer feature of VAX/VMS -- over to Windows NT, it would h...

There is of course more than one way for BBC Basic to be fast: maybe it's faster with single-letter variable names? Maybe FOR would have been faster than REPEAT? Maybe it's fair game to use integer variables where applicable? BBC BASIC is fastest of all with the permanent variables A%-Z%, then with...

In Assembler, I tend to JSR to the beginning of loops I might need to break out of prematurely, precisely in order to be able to accomplish that breaking out with little besides an RTS (perhaps a flag set or register load). The equivalent of this in BASIC would be to move your whole FOR loop into a ...

I don't mind the lack of spaces; I got so used to living without them, my brain tends to put them there for me. You can even miss out more spaces than you would normally ever get away with, if you use a slight hack: insert a token directly into your program, either by VDUing its token code to the sc...

Indeed BBC BASIC is particularly slow in one regard: the way that GOTO and GOSUB find their destination line by a linear search starting at the beginning of the program every time Microsoft BASIC at least does the same thing (searching linearly that is -it does start from the current line if the de...

And here is the utilities disc that goes with it. FP06 is a BASIC program which generates a footprints database from DATA statements in the program. (It was easier to get this working than a full-blown editor .....). Just run it and copy the command it produces. Footprint name is up to 7 characters,...

Latest SSD image:
Now has Load and Save commands. Also a tech preview of what will be OL, but accessed as Y.

Putting the constant on the left-hand side of the = test is a common idiom in C-derived languages, to guard against accidentally redefining a variable you are trying to read the value of. This is because in C, Java, JavaScript, Perl &c., one = is "telling" and two == is "asking"; and if you use some...

There's nothing wrong with using a Zener diode across the collector and emitter of a transistor which is being used to switch an inductive load; but it must have a PIV somewhere between the supply voltage and the PIV of the collector-base junction.

Well, I finally got my hands on some Servisol Super 10 and managed to get four out of five of the faulty key switches responding perfectly with just a good squirt and a few hundred cycles each. The last one needs a bit more attention; it's not an especially heavily-used position (top row 5 and %) so...

Not necessarily. With highly proprietary stuff, there may be "free" and "paid-for" client software, with the former having some of the latter's features deliberately nobbled. BitKeeper was an example of such (although Andrew Tridgell's Open Source client managed to outperform even the paid-for one).

I got stuck with the photoplotting stuff and ended up going on a wild tangent, rewriting the maths library (it now does multiplications in about half the time it used to, and divisions in something nearer a third than half the time it used to. Getting this to work required rearranging zero page loca...

That and all .....

This is why, when you ask a user to supply a filename, you should never, ever presume to know what is or is not a valid filename.

The most important tool you need for host-side development is a good text editor, because you will be using it. A lot. Ask six different people, and you will get twelve different answers. Try them all, and any more you can find; and whichever one you choose, be sure occasionally to have a play with ...

If you were going to do 640*256*4 or 320*256*16, you really would need a framebuffer that looks as though it is composed of 20480 16-bit words of RAM. The circuitry is capable of sending 640 pixels to the screen on each scanline; it just can't read more than 80 bytes from memory in that time. But if...

I acquired this new toy today: IMG_20200904_231820_1280.jpg It is not quite as perfect as it looks; as explained by the seller, some of the keys are not working. However, the action on them is perfect, so they probably just need a squirt of Servisol and a bit of Micro Olympics to get them going agai...

Well, it seems to work, behaves exactly as expected and does not do anything too crazy with the stack either (as shown by selecting a graphics mode and changing HIMEM to somewhere inside the framebuffer).

I think we've all seen assembler code like this: .add16 CLC .adc16 JSRadd16_1 .add16_1 LDAwkspace,X ADCwkspace,Y STAwkspace,X INX INY RTS with multiple entry points into the same code, so two JSRs can hit the same RTS. Can you do something similar in BASIC, with a DEFPROC between another DEFPROC and...

Mmm, I'm sure there's some good stuff in there! I think I even have a use for the CRTC stunts they pulled .....

See VList source code. I'm certainly not claiming any originality on this idea, and it would be disingenuous of me to pretend that the name jgharston did not crop up a few times while I was searching for information on how to do this! However, as a fan of doing things the hard way just for fun, I t...

Although I'm currently using BeebAsm for BCP development, and it's going very nicely, I do not want to abandon the idea of it being buildable on the target side. Otherwise, I am going to wind up with not so much a BBC Micro app, but a PC app that uses a special tool chain (BeebAsm and friends) and r...

In case you need help with detokenising line numbers, this is how DFSbuster does it: Line numbers in a GOTO / GOSUB / RESTORE are tokenised according to a slightly weird scheme to ensure they don't clash with anything else that might look like a token; elsif ($code == 141) { # 141 = line number ($ln...

^ This is caused by BeebEm trying to detect double-sided discs. It gets tripped up when sector 10 contains mostly ASCII data (i.e. values &20-&7F), as often happens in games that have instructions in their loader. Ah! That might go some way towards explaining some of my past BeebEm woes with disc i...