Date: Wed, 16 Feb 2000 08:55:02 +0200 (IST) From: Eli Zaretskii X-Sender: eliz AT is To: Florian X cc: djgpp AT delorie DOT com Subject: Re: extender/DPMI host/ DPMI surver In-Reply-To: <38a9b77a$0$85200@SSP1NO17.highway.telekom.at> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Reply-To: djgpp AT delorie DOT com Errors-To: dj-admin AT delorie DOT com X-Mailing-List: djgpp AT delorie DOT com X-Unsubscribes-To: listserv AT delorie DOT com Precedence: bulk On Tue, 15 Feb 2000, Florian X wrote: > What is the difference betweenan extender, a DPMI host, and a DPMI surver? This is a subject for a book, not for a short message in a news group... In a nutshell, a DOS extender and a DPMI server are two ways for letting protected-mode programs to run on top of DOS. An extender does this in a more transparent way: it catches DOS/BIOS calls made from protected mode and reissues them in real mode after moving the buffers between conventional and extended memory. Since the application never knows its calls were intercepted, the application code can be the same one as in a real-mode program. In contrast, the DPMI way provides only primitive services for running PM code on DOS. Thus, it needs more processing from the application which needs to call these services explicitly. (In DJGPP, this added processing is mostly handled by the low-level library functions such as __dpmi_int and dosmemput). See the "DJGPP Overview" page, accessible from www.delorie.com/djgpp/, for more about this.