Différences

Ci-dessous, les différences entre deux révisions de la page.

--- back2root:ibm-pc-ms-dos:interrupts:int_21_34 [2023/01/08 11:46] – [Notes & Comments] frater
+++ back2root:ibm-pc-ms-dos:interrupts:int_21:int_21_34 [2023/01/10 11:55] – supprimée - modification externe (Unknown date) 127.0.0.1
@@ Ligne 1: / Ligne 1: @@
-====== INT 0x21 - 0x34 - Get Address to DOS Critical Flag ======
-<WRAP round info >
-INDOS (Undocumented DOS 2.0+)
-</WRAP>
-===== Request/Call: =====
-{{tablelayout?rowsHeaderSource=Auto&colwidth=""}}
-^  reg  ^  value  ^  descr  ^
-|  AH   |  0x34   |         |
-===== Return: =====
-{{tablelayout?rowsHeaderSource=Auto&colwidth=""}}
-^  reg  ^   descr  ^
-|  ES:BX  | address of a byte indicating whether a DOS call is in progress. No DOS calls should be made if set.  |
-===== Notes & Comments =====
-<WRAP round box>
-  * AKA the INDOS flag, this critical section flag may be checked from within an interrupt handler before requesting a DOS service. It is a semaphore that is non-zero when DOS is busy, and zero otherwise.
-  * though this flag indicates whether a DOS interrupt is active, it should not be used alone to determine DOS is safe for re-entry; Here's the standard rule for safe DOS entry: if [[back2root:ibm-pc-ms-dos:interrupts:int_28|INT 28]] is active or this flag and the critical error flag are clear then it is safe to call DOS
-  * this interrupt should be used only during TSR initialization; the returned pointer should be used thereafter
-  * this flag is cleared after a critical error ([[back2root:ibm-pc-ms-dos:interrupts:int_24|INT 24]])
-    * ES:BX-1 points to the critical error flag for DOS 3.x+
-    * ES:BX+1 points to the critical error flag for DOS 2.x
-    * ES:BX-1AA points to the critical error flag for COMPAQ DOS 3.0
-INT [[back2root:ibm-pc-ms-dos:interrupts:int_21_5d|21,5D]] in DOS 3.x+ can be used to locate the critical error flag</WRAP>