Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!apple!dlyons From: dlyons@Apple.COM (David A. Lyons) Newsgroups: comp.sys.apple2 Subject: Re: ProDOS Question Message-ID: <42405@apple.Apple.COM> Date: 27 Jun 90 07:53:55 GMT References: <507.infoapple.net@pro-generic> Organization: Apple Computer Inc, Cupertino, CA Lines: 33 In article <507.infoapple.net@pro-generic> sb@pro-generic.cts.com (Stephen Brown) writes: >I have a couple questions about ProDOS. I have been reading my trusty Beneath >Apple ProDOS, and have become confused. > >When it talks about the ONLINE (return names of one or all online volumes) MLI >call, it says that it will return the name of 1 volume if a specific unit >number is specified, in which case a 16 byte buffer is needed. It then goes >on to say that if a zero (non specific) unit number is used, all volumes' names >will be provided, and a 256 byte buffer will will be needed. But I thought only >14 volumes were supported, which requires 14*16=224 bytes! I checked the >reference card, and indeed, in the system global page, there are 16 places in >the device driver address table, but two (for slot 0) are reserved. >Why is a 256 byte buffer needed? You're right--only 256-32 bytes generally get filled with useful information. Consider the extra space "room for expansion"--maybe ProDOS 8 will return something useful to you there someday (as someone already pointed out, you can manage 15 devices if you cheat a little and use slot 0 drive 2...and if the system has a device that doesn't allow any block-level access, like a network server, I don't see why it couldn't use slot 0 drive 1, giving you a total of 16 devices). Another possible answer (multiple choice, take your pick :-) : You need 256 bytes because that's how much ProDOS 8 pre-fills with zeroes before it starts filling your buffer with interesting stuff. -- David A. Lyons, Apple Computer, Inc. | DAL Systems Apple II Developer Technical Support | P.O. Box 875 America Online: Dave Lyons | Cupertino, CA 95015-0875 GEnie: D.LYONS2 or DAVE.LYONS CompuServe: 72177,3233 Internet/BITNET: dlyons@apple.com UUCP: ...!ames!apple!dlyons My opinions are my own, not Apple's.