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When my laptop's hdd was failing, reads of bad sectors were taking 30 seconds to time out. So even though there wasn't much going on the disk often appeared to be very busy. You can use iotop to see what processes are using the disk. However, if it's not installed I wouldn't bother because installin...

I don't know anything about Macs but that won't stop me commenting either! It's using a reverse DNS scheme. The idea is that anyone can create a globally unique identifier using a domain that they control. So the "com.acorn." namespace is reserved for the clothing retailer acorn.com. So if you're lo...

The -opt parameter only accepts the boot option (i.e. miss out the 4):
Or if you have a -boot parameter it defaults to boot option 3 so you can leave it out:

Could do with a narrow and wide variant. You're right. I was thinking (from a programmer's point of view) that it is very easy to stretch the text when you render it, but that's not much use if a particular application doesn't have that feature. So it needs variants for modes 0, 1, 2, 3 and 6. At t...

the glyphs can occupy any proportion of that square. True, although a traditional typographer (and I was brought up with metal type) might raise an eyebrow! The font doesn't have any leading. Descenders on one row meet capitals on the next to reproduce the beeb look. I would have preferred it to re...

There's some slight fringing in OS X Emacs, I assume because of anti-aliasing. On Windows, horizontal fringing seems unavoidable in apps that use sub-pixel anti-aliasing, but it's perfect with regular anti-aliasing. The horizontal fringing is not as rough as your OS X example though. What point siz...

9pt text on a 96dpi screen is exactly 8x8 pixels. I can't quite see how that works out. 9pt is 1/8" (72 points to an inch), so at 96dpi shouldn't that be 12 pixels? I appreciate that there may be an adjustment for leading. Truetype scales the "em square" according to your calculation, but the glyph...

Cheers. 12 would have been a more natural em-size but true-type won't go below 16.

I was looking for a beeb true-type font but I couldn't find one with the original spacing so I made one. Oddly, the Master font in the Welcome Guide is different from the font in the MOS 3.20 ROM in beebem. The former has an obvious error in Æ (and several other glitches) so I used the latter. The a...

I made the wrong trade off with the dragon. Having the NEXT before the PLOT avoids pointlessly redrawing loads of points, but also throws away a lot of new points that were expensive to calculate. Just moving the NEXT from before the PLOT to after the PLOT speeds things up greatly. Also: Different s...

I did a Hilbert curve but that was 31 lines of code, much of it fiddly. So I did this instead. It's much simpler, but really slow. Possibly too slow to be of interest on a real beeb. 10REM ctr - dragon curve ifs 20MODE0 30VDU23,1,0;0;0;0; 40S=1/SQR(2) 50A=S*COS(PI/4):B=S*SIN(PI/4) 60C=S*COS(3*PI/4):...

the ULA reads the byte from memory, and the xyz are the correct bit values from the byte it read, ie, they're actually values intended for other pixels, but if you've programmed the palette 'correctly' for the mode then all possible entries for 1xyz (ie 1000, 1001, 1010, etc) give you the same outp...

I shouldn't have used the term 'speckling', I was meaning to refer to the 'noise' that Tom Seddon and Tricky referred to, where on some of their Beebs (but apparently not Masters?) some of the bits end up as random values, not 1s as expected. Which seems like a serious defect! It's not a problem in...

Cheers, with this clue I went looking in the MOS. Having calculated the 10-bit frequency period value to write to the chip (in &83D and &83E) the code at &ED6F adds in a constant channel fudge factor from a lookup table at &C441 . (Confusingly, the channel number is represented by a value in X betwe...

When I play the same note on two different channels I get two different pitches. I've tried this on beebem, b-em and b2 with consistent results but not a real beeb. Can anyone reproduce it? It's surprising that these emulators all do this, but I'd also be surprised if a real beeb worked like this. T...

I certainly wasn't aware of that, and should anybody care neither BBC BASIC for Windows nor BBC BASIC for SDL 2.0 emulates the behaviour described here. In fact using them it isn't possible to generate, using ENVELOPE, an alternating tone with equal durations. Because the pitch envelope has an odd ...

I was trying to create a simple envelope that alternated between two pitches but it was more trouble than I expected because there are a couple of errors in the BBC User Guide. I ended up using Audacity to look at the sound output to see exactly what was going on. To save anyone else the bother... T...

may be should also allow Bitmap Image, as thats what BeebEm414 defaults to for capture screen for high scores! had to change it in paint prog to jPeg, but lost quality of pic :( On the menu in beebem select: File | Screen Capture Options | PNG Format then select: Options | Save Preferences and you ...

The perspective might not be quite right... 10REM ctr - spherical spiral 20MODE0 30REM number of steps: 40R%=2500 50H%=R%/2 60REM rotated towards viewer by: 70R=-PI/4 80U=COS(R):V=SIN(R) 90PROCP(4,0) 100FORI%=1TOR% 110PROCP(5,I%) 120NEXT 130END 140DEFPROCP(C%,S%) 150T=PI*(S%-H%)/R% 160C=COS(T) 170X=...

They are right at the start. Try this on a beeb. 10MODE4 20S%=&5800 30C%=&C000 40FORI%=0TO&2FF 50S%?I%=C%?I% 60NEXT Each char is eight bytes, one byte for each row, eight pixels in each byte. Most significant bit on the left, least significant on the right. Edit: This is true on a Model B; the Maste...

Only 35 years or so left to wait. Isn't it 70 years after the death of the author? (as per "Written, dramatic, musical and artistic work") https://www.gov.uk/copyright/how-long-copyright-lasts You're right. I always thought there was a separate rule for works-for-hire, but I just checked and that's...

To me this implies double-height backgrounds only get copied down after Double Height 0x8D, and stop getting copied down after Normal Height 0x8C. I read it the other way. "The remaining Character Rectangles" refers to the character rectangles that aren't in double height. So the background is copi...

This might help. Maybe. I used Wolfram-Alpha to calculate the [3/3] pade approximant of (ln(1+x)-x)/x^2 (as used in BASIC2's LN) and then converted it to a continued fraction. This gave the same seven terms as calculating the continued fraction directly. Pade approximants of taylor series and trunc...

The redoubtable Bruce Clark has posted some type-ins over here: http://forum.6502.org/viewtopic.php?p=60765#p60765 In the third program edit line 60 to change the plus to a minus: - 60 PRINT CHR$(32+3*(C-INT(C)<.4)); + 60 PRINT CHR$(32-3*(C-INT(C)<.4)); I guess Apple BASIC uses +1 for TRUE. In the ...

I don't know if this is helpful, but somewhat to my amazement I've been able to find the original BBC BASIC program It is, but I now realise I got the wrong end of the stick. This is useful for the polynomial approximations, but not the continued fraction ones. I checked that the continued fraction...

C99 and C++17 both support hexadecimal floating point constants so it should be possible to exactly represent the beeb's 40-bit constants. Somehow I'd got the idea that early BBC Basic versions used the ratio of two polynomials, but that seems not to be the case. You were right. The beeb uses contin...

Unless there's some other code you're not posting which makes the css rule domain specific, adding things like that seem like a very bad idea to me. I would recommend using an element blocker like ublock origin for things like that. I like living dangerously! But it's a fair point. Here's a ublock ...

danielj wrote: ↑

Sun Jun 17, 2018 6:32 pm

can the same be done in Chrome?

I don't use Chrome but a quick Google search suggests they removed the built-in feature. Apparently you can get add-ons for Chrome that let you do this.

Edit: there's a safer method below. You can hide these messages locally by adding .notice {display:none} to your browser's user-defined css. In Firefox this is in the file: C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>\chrome\userContent.css You could use greasemonkey to do some...

Yes, that's right. I find it helpful to remember that the value at the top of the stack is always at &101+S (ignoring when S=&FF). I guess the original return address is still sitting there at &10B/C+X, and would need to be removed at some stage. At the start of .code2 it gets overwritten by the new...