AWCTTYPA@UIAMVS.BITNET ("David A. Lyons") (05/15/88)
>Date: Sun, 8 May 88 01:03:08 GMT >Reply-To: Info-Apple@BRL.ARPA >From: steinmetz!glacier!elliott@itsgw.rpi.edu >Subject: davex problems and some system program questions >Now, the real point of my posting: It's become clear to me that the >rules have been changing a little since my last big bout of >programming. The davex documentation mentions the concept of system >programs having "startup buffers" where parameters can be stored. This >is either an undocumented standard, or newer than my (1983?) ProDOS >technical reference manual. Can someone explain the details of how >these work? Startup buffers were not around in 1983, but they are now an actual offical standard, documented in ProDOS Technical notes #7 and #14. These are available from APDA, the Apple Programmers and Developers Association (290 SW 43rd Street, Renton WA 98055; (206) 251-6548). The technotes may also be available from your local users group; they can be distributed freely. They are also available on services like CompuServe and GEnie; I don't know if they are available from any network servers or FTP sites or not. >Also, in the section describing system programs, the manual details >how to load another system routine, but nowhere does it explain the >standard quitting mechanism that many system programs seem to use, Quitting is easy: Just JSR $BF00, DFB $65, DW PARMS. PARMS: DFB 0,0,0,0,0,0 The ugly standard "enter prefix"/"enter pathname" thing is DOCUMENTED as being stored as $D100-$D3FF in the language card, so program selectors can take advantage of that to replace it with a routine that re-loads the selector program instead of prompting for the next application info. The startup buffer convention goes like this: Just start your SYS file with the following: JMP xxxx DFB $EE,$EE,Length-of-buffer DS enough space for a length-prefixed string; put a default here, and the program that runs you has the option of replacing it with another string if it wants. xxxx: ... > > Jim Elliott / ...!seismo!uunet!steinmetz!crd!elliott > / > "Don't look, son, it's / Jim_Elliott%mts@itsgw.rpi.edu [school] > a secular humanist!" / (or) elliott@ge-crd.arpa [work] --David A. Lyons a.k.a. DAL Systems PO Box 287 | North Liberty, IA 52317 BITNET: AWCTTYPA@UIAMVS CompuServe: 72177,3233 GEnie mail: D.LYONS2