83 lines
2.1 KiB
HTML
83 lines
2.1 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
|
|
|
|
<html>
|
|
|
|
<head>
|
|
<meta http-equiv="Content-Type"
|
|
content="text-html; charset=Windows-1252">
|
|
<title>INT 21,34 - Get Address to DOS Critical Flag INDOS</title>
|
|
<meta name="FORMATTER" content="Microsoft FrontPage 2.0">
|
|
</head>
|
|
|
|
<body>
|
|
|
|
<h1><a name="kap_interrupt_1940"></a>INT 21,34 - Get Address to
|
|
DOS Critical Flag INDOS (Undocumented DOS 2.0+)</h1>
|
|
|
|
<p> AH = 34h</p>
|
|
|
|
<p> on return:</p>
|
|
|
|
<p> ES:BX = address of a byte indicating whether a DOS call is</p>
|
|
|
|
<p> in progress. No DOS calls should be made if set.</p>
|
|
|
|
<p> - AKA the INDOS flag, this critical section flag may be
|
|
checked from</p>
|
|
|
|
<p> within an interrupt handler before requesting a DOS service.
|
|
It is</p>
|
|
|
|
<p> a semaphore that is non-zero when DOS is busy, and zero
|
|
otherwise.</p>
|
|
|
|
<p> - though this flag indicates whether a DOS interrupt is
|
|
active, it</p>
|
|
|
|
<p> should not be used alone to determine DOS is safe for
|
|
re-entry;</p>
|
|
|
|
<p> Here's the standard rule for safe DOS entry: if ~INT 28~ is
|
|
active</p>
|
|
|
|
<p> or this flag and the critical error flag are clear then it is
|
|
safe</p>
|
|
|
|
<p> to call DOS</p>
|
|
|
|
<p> - this interrupt should be used only during TSR
|
|
initialization;</p>
|
|
|
|
<p> the returned pointer should be used thereafter</p>
|
|
|
|
<p> - this flag is cleared after a critical error (~INT 24~)</p>
|
|
|
|
<p> - ES:BX-1 points to the critical error flag for DOS 3.x+</p>
|
|
|
|
<p> ES:BX+1 points to the critical error flag for DOS 2.x</p>
|
|
|
|
<p> ES:BX-1AA points to the critical error flag for COMPAQ DOS
|
|
3.0</p>
|
|
|
|
<p> ~INT 21,5D~ in DOS 3.x+ can be used to locate the critical</p>
|
|
|
|
<p> error flag</p>
|
|
|
|
<hr>
|
|
|
|
<table border="0" width="100%" cols="3">
|
|
<tr>
|
|
<td width="33%">Zurück zum <a href="inte1at0.htm">Interrupt
|
|
Info</a>. </td>
|
|
<td align="center" width="33%"><a
|
|
href="mailto:Roger.Morgan@htl-steyr.ac.at">Roger Morgan</a>
|
|
/ 1998 </td>
|
|
<td align="right" width="33%"><font size="1">L.Änderung <!--webbot
|
|
bot="Timestamp" s-type="EDITED" s-format="%d.%m.%y"
|
|
startspan -->29.03.99<!--webbot bot="Timestamp" endspan
|
|
i-checksum="13964" --> </font></td>
|
|
</tr>
|
|
</table>
|
|
</body>
|
|
</html>
|