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From: dhinds@portia.Stanford.EDU (David Hinds)
Newsgroups: comp.sys.ibm.pc
Subject: Re: int 13h vs. int 21h disk I/O confusion
Summary: Int 13h is a BIOS call, and Int 21h is an DOS call
Message-ID: <8355@portia.Stanford.EDU>
Date: 18 Jan 90 03:47:59 GMT
References: <26038@cup.portal.com>
Sender: David Hinds <dhinds@Portia.stanford.edu>
Organization: Stanford University
Lines: 16

In article <26038@cup.portal.com>, cliffhanger@cup.portal.com (Cliff C Heyer) writes:
> Books explain int 21h calls as being more 
> functional and portable than int 13h calls.
> But I'm wondering if there other important
> benefits of one method vs. the other.
> 
    Int 13h points to the BIOS low-level disk I/O routines.  It does only
low-level I/O - like seek to track n, and read m sectors.  Programs running
under DOS should never use it, because it bypasses DOS's file structure,
and using it can easily trash your disks.  It works independent of DOS,
and knows nothing about device drivers.  Int 21h is the standard entry
point for all DOS services.  I doubt that any compiler's I/O library would
use Int 13h calls, because they would be nothing but trouble.

-David Hinds
 dhinds@portia.stanford.edu