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

--- back2root:ibm-pc-ms-dos:interrupts:int_21:int_21_30 [2024/01/19 23:19] – créée frater
+++ back2root:ibm-pc-ms-dos:interrupts:int_21:int_21_30 [2024/01/19 23:23] (Version actuelle) – [Return:] frater
@@ Ligne 1: / Ligne 1: @@
-====== INT 0x21 - 0x34 - Get DOS version ======
+====== INT 0x21 - 0x30 - Get DOS version (DOS 2+) ======
-<WRAP round info >
-INDOS (Undocumented DOS 2.0+)
-</WRAP>
 ===== Request/Call: =====
@@ Ligne 15: / Ligne 11: @@
 {{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.  |
+|  AL  | Major version (2 -> x) |
+|  AL  | Minor version (in hundredth decimal) |
+|  BH  | 0xFF: indicates MS-DOS, only if OEM vendor chooses to identify\\ 0x00: indicates PC-DOS  |
+|  BL:CX  | 24bit OEM Serial number if BH = 0xFF  |
 ===== 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.
+  * for an example DOS version 2.1 returns AL=2 and AH=10
-  * 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
+  * DOS versions prior to DOS 2.0 return zero in AH and AL
-  * this interrupt should be used only during TSR initialization; the returned pointer should be used thereafter
+  * DOS version 4.0 and 4.1 usually return the same value of 4.00
-  * this flag is cleared after a critical error ([[back2root:ibm-pc-ms-dos:interrupts:int_24|INT 24]])
+  * the OEM serial number is a rarity, though some older OEM DOS versions implemented this feature
-    * ES:BX-1 points to the critical error flag for DOS 3.x+
+  * the OS/2 compatibility box returns 10.10 for OS/2 1.1, 10.20 for OS/2 1.2, etc...
-    * ES:BX+1 points to the critical error flag for DOS 2.x
+  * when testing for version, a specific test can often cause your code to not work in following versions of DOS.  It is often better to test for a version number greater or equal to the minimum rather than a specific version number where possible
-    * ES:BX-1AA points to the critical error flag for COMPAQ DOS 3.0
+</WRAP>
-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>
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