Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site voder.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!houxm!vax135!cornell!uw-beaver!tektronix!hplabs!nsc!voder!gbs From: gbs@voder.UUCP (George Smith) Newsgroups: net.micro.pc Subject: Re: How does a program detect disks on a PC? Message-ID: <868@voder.UUCP> Date: Thu, 26-Sep-85 13:52:43 EDT Article-I.D.: voder.868 Posted: Thu Sep 26 13:52:43 1985 Date-Received: Mon, 30-Sep-85 01:46:13 EDT References: <1054@phs.UUCP> <473@ecsvax.UUCP> Distribution: net Organization: National Semiconductor, Santa Clara Lines: 36 > > It appears to me, from reading the documentation, that the correct way > to determine how many disks DOS thinks there are is through the DOS > function call Select Disk (0E hex). > Unfortunately, the number DOS is returning seems to bear little > relationship to the number of disk devices DOS currently knows about. > Running DOS 3.10 on an IBM-PC/XT I get 5 drives. This doesn't change > whether or not I have my ramdisk device driver installed. > > -Bennett The IBM DOS Technical Reference Manual for DOS 2.1 might lead you to believe that the Select Disk Function (0EH) will supply you with the information you want. However, the Microsoft MS-DOS Programmers Reference Manual includes the following large notice on the page describing function 0EH: +----------------------------------------------------------+ | | | NOTICE | | | | For future compatibility, treat the value returned in | | AL with care. For example, if AL returns 5, it is not | | safe to assume drives A, B, C, D, and E are all valid | | drive designators. | | | +----------------------------------------------------------+ If anyone knows how to find out the number of drives currently available to running software, please post this information to the net. -- George B. Smith National Semiconductor ...!{ihnp4!nsc | decvax!decwrl!nsc | ucbvax}!voder!gbs