From: Brian Ketterling (tweel8502_at_hotmail.com)
Date: 2003-10-28 01:18:28
>From: Willi Kusche <email@example.com> > >On 25-Oct-03, Brian wrote: >->According to "Machine Language 302" by Rick Nash, in Loadstar's "Compleat >->Programmer" collection: > >->"$BC9B converts floating point to four byte integer. JSR with floating >->point number stored in FAC1. Result will be stored in locations >$62-$65." > > I quite certain that the conversion is to a two byte integer. $62 and >$63 >must be zeros. No, I checked and it works. "Mapping the 64" adds that it's a signed integer, and sure enough it reserves bit 31 for a negative flag. The integer is stored in high-endian fashion, so e.g. 2^30 looks like this: 01000000 00000000 00000000 00000000 ($62) ($63) ($64) ($65) and -1 looks like this: 10000000 00000000 00000000 00000001 >From: john/lori <firstname.lastname@example.org> > >you might have a look at this: > >http://www.hut.fi/Misc/cbm/docs/c64-diss.html#B37D > >(B391 right after the FRE function which is at B37D, the closest >link I could find) > >(I have no idea what it does, but it sounds right ;) Dang, no, that's one of the standard int->fac1 routines. That one converts a 16-bit integer in .A/.Y to a floating point #. Good detective work though. I didn't know about that searchable disassembly -- thanks! Well, if there really isn't a routine to convert a 4-byte integer to a floating point number, I guess I could do a workaround, like convert the 1st two bytes, multiply by 65536, then convert the next two bytes and add. I wonder why that 4-byte routine exists, though? -- especially if there's no routine to convert back. -- Brian _________________________________________________________________ Fretting that your Hotmail account may expire because you forgot to sign in enough? Get Hotmail Extra Storage today! http://join.msn.com/?PAGE=features/es Message was sent through the cbm-hackers mailing list
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