Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!husc6!cmcl2!rutgers!rochester!rocksanne!rocksvax!martyl From: martyl@rocksvax.UUCP (Marty Leisner) Newsgroups: comp.sys.ibm.pc Subject: Re: Help with interrupt 52 Message-ID: <156@rocksvax.UUCP> Date: Wed, 14-Oct-87 14:27:59 EDT Article-I.D.: rocksvax.156 Posted: Wed Oct 14 14:27:59 1987 Date-Received: Sat, 17-Oct-87 03:50:05 EDT References: <11819@decwrl.DEC.COM> Reply-To: martyl@rocksvax.UUCP (Marty Leisner) Organization: Xerox: Henrietta, NY Lines: 62 In article <11819@decwrl.DEC.COM> fulton@comet.dec.com (Cathy Fulton -- CXO Technical Training) writes: > > Does anyone have info on what interrupt 52H does? It is an > undocumented interrupt. It is a pointer to the start of a chain > of blocks that tells you what programs DOS has loaded in memory. > I am mainly interested in finding out what the format of these > blocks are. > This is the information I have from the list posted by Ralf Brown and Dan Lanciani. If anyone has more complete information, I'd like to see it. INT 21 - Internal - Get Disk List AH = 52H Return: ES:BX points to DOS list of lists List of Lists: Bytes Value 0-3 Pointer to first DOS disk block (see func 36H) 4-7 Partially Unknown. Pointer to a device driver. Maybe first resident driver? 8-B Partially Unknown. Pointer to a device driver. Maybe first resident character device driver? C-F Pointer to actual CON: device driver, whether installable or resident 10-11 Unknown. 0200H. A byte/blocksize value??? 12-15 Unknown. Pointer to current directory block???? 16-19 Partially Undefined: Pointer to array of drive info: 51H bytes per drive, starting with A: ... 00-3F Current path as ASCIIZ, starting with 'x:\' 40-43 Unknown. I see zeros always 44 Unknown. Flags? I see 40H, except for entry after last valid entry = 00H 45-48 Pointer to DOS Disk Block for this drive 49-4A Unknown. Current track or block? -1 if never accessed. 4B-4E Unknown. I see -1 always 4F-52 Unknown. I see 2 always 1A-1D Unknown. Pointer to data area, maybe including cluster allocation table? 1E-1F Unknown. I see zero always 20 Unknown. May be number of block devices. 21 Unknown. May be number of resident devices or ??? (5 always) 22 Beginning (not a pointer. The real beginning!) of NUL device driver. This is the first device on DOS's linked list of device drivers. ------------------------------------------------ Flame on!! I really hate this reverse engineering. Anyone with source code who wants to leak (??) what's going on. Flame off!! marty -- marty leisner xerox corp leisner.henr@xerox.com martyl@rocksvax.uucp