The first addition to the calculator port is the TIME$ keyword, which lets you get or set the system time.
That's all very well and good, but only the TI-84+ calculator has real-time clock hardware - the TI-83+ doesn't have any sort of accurate timekeeping to speak of. Rather than display an error when TIME$ is used I opted to use an inaccurate software-based clock. It uses the TI-83+'s timer interrupts (roughly 118Hz) to update the date and time about once a second. The clock is reset to Mon,01 Jan 2001.00:00:00 every time BBC BASIC is restarted and keeps abysmal time, but software designed to use the clock will at least run.
I have been transferring and amending documentation from Richard Russell's website to a private installation of MediaWiki. There are about 120 entries so far; having documentation puts me much closer to being able to make a release.
I have also fixed a handful of bugs. One that had me tearing my hair out was something like this:
250 DEF PROC_someproc(a,b) 260 a=a*PI 270 ENDPROCThe program kept displaying a No such variable error on line 260. Well, a is clearly defined, and retyping the procedure in another program worked, so what was the problem here? I thought that maybe one of the graphics calls or similar was corrupting some important memory or modifying a register it shouldn't. It turns out that the problem lay in the Windows-based tokeniser - it was not picking up PI as a token, for starters, and was storing the ASCII string "PI" instead. On top of that, it was treating anything after a * as a star command, which aren't tokenised either. (Star commands, such as *REFRESH, are passed directly to the host interface or OS). Retyping the problematic lines caused BBC BASIC to retokenise them, which was why I couldn't replicate the problem in other programs. By fixing the tokeniser, everything started working again.
The source code for the analogue clock program is listed below.
10 *REFRESH OFF 20 VDU 29,48;32; 30 GCOL 0,128 40 REPEAT 50 t$=TIME$ 60 hour%=VAL(MID$(t$,17,2))MOD12 70 min%=VAL(MID$(t$,20,2)) 80 sec%=VAL(MID$(t$,23,2)) 90 sec=sec%/60 100 min=(min%+sec)/60 110 hour=(hour%+min)/12 120 CLG 130 GCOL 0,127 140 MOVE 0,0 150 PLOT 153,31,0 160 GCOL 0,0 170 FOR h=1TO12 180 hA= h/6*PI 190 hX=30*SIN(hA) 200 hY=30*COS(hA) 210 MOVE hX,hY 220 DRAW hX*0.9,hY*0.9 230 NEXT h 240 PROC_drawHand(sec,30) 250 PROC_drawHand(min,24) 260 PROC_drawHand(hour,16) 270 *REFRESH 280 UNTIL INKEY(0)<>-1 290 *REFRESH ON 300 END 310 DEF PROC_drawHand(pos,length) 320 MOVE 0,0 330 pos=pos*2*PI 340 DRAW length*SIN(pos),-length*COS(pos) 350 ENDPROCI translated the tokeniser source code to PHP so that by pointing a browser to file.bbcs for a known file.bbc the highlighted, detokenised source code is served as HTML instead. Hurrah for mod_rewrite, and if you're using IIS Ionic's Isapi Rewrite Filter performs a similar job using the same syntax.
