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Q69974: Information Regarding Buffered I/O and MSCDEX

Article: Q69974
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.0
Operating System(s): 
Keyword(s): kb16bitonly
Last Modified: 06-NOV-1999

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The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) 3.0 
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SUMMARY
=======

In the Microsoft Multimedia Windows environment, the MSCDEX driver provides
buffered input and output (I/O) from the CD-ROM device. The information below
discusses using buffered I/O in an application.

MORE INFORMATION
================

When 32K of data is read from the disk in response to a request from an
application, 32K additional data is read from the disk into a buffer in
anticipation of another sequential read request.

Currently, all information read from the CD-ROM is in response to a synchronous
MS-DOS file I/O request. This prevents an application from requesting that a
particular portion of data be read from the disk while the application performs
some other processing. Although an implementation of asynchronous I/O is being
researched, it will not be implemented soon. It would be necessary to rewrite
all CD-ROM drivers currently in use to implement asynchronous I/O.

To fill the buffer with an arbitrary selection from the CD-ROM, an application
can request one byte of data from the beginning of the selection to be read.
After the CD-ROM seeks to the data and reads one byte, control is returned. The
driver reads the remainder of the data into the buffer asynchronously.

Additional query words: no32bit 3.00

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Keywords          : kb16bitonly 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK300
Version           : WINDOWS:3.0

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