DOS ain't dead - AMIS, Optimize memory usage

AMIS, Optimize memory usage (Developers)

posted by Japheth , Germany (South), 13.05.2011, 07:28

> That precaution probably seemed necessary to the seasoned (and
> cautious) professional programmer but, oyez! oyez! hear...!, both
> the clueless newbie (confused anyway with all that there interrupt stuff),
> AND... the "good (TM)" programmer (after carefully checking his facts) will
> omit the flag save/restore (thereby reducing the size of the
> resident KBFR by a whopping 6 bytes iirc) :=)

Cool!

> The reason a software int 15h "hook" does not need to preserve the running
> flags is, of course, that no information is passed "down" thru them and,
> conversely, in cases information has to be passed back "up" to the
> (initial) caller, it is by altering the flags image put on the stack by the
> initial int 15 caller, not the running flags.

This is true ............ to some degree. :))

However ... there are a few considerations:

- int 15h is an interrupt which is used for a lot of purposes.
- there exists software, including BIOSes, which do NOT return
from this interrupt by an IRET, but by a RETF 2.
- a lot of software sets (or resets) the carry flag BEFORE it calls Int 15h.
( this is probably done because there exist buggy hookers/BIOSes ).

So, considering these facts(?), one might come to realize that it is at least "thinkable" that saving the flags status is not absolutely useless. I guess - it was in 1993! - that was the reason why I added it.

---
MS-DOS forever!

Post reply

Complete thread:

int 15/4f French keyboard driver ready + *Ping Japheth* - Ninho, 27.04.2011, 13:34 (Developers)
- int 15/4f French keyboard driver ready + *Ping Japheth* - Japheth, 27.04.2011, 16:02
  - int 15/4f French keyboard driver ready + *Ping Japheth* - Ninho, 27.04.2011, 17:13
    - int 15/4f French keyboard driver ready + *Ping Japheth* - Japheth, 28.04.2011, 07:47
- int 15/4f French keyboard driver ready + Now what? * - Ninho, 10.05.2011, 13:30
  - int 15/4f French keyboard driver ready + Now what? * - Rugxulo, 10.05.2011, 23:52
    - int 15/4f French keyboard driver ready + Now what? * - Ninho, 11.05.2011, 13:38
      - int 15/4f French keyboard driver ready + Now what? * - ecm, 11.05.2011, 19:39
        int 15/4f French keyboard driver ready + Now what? * - Ninho, 12.05.2011, 10:56
        int 15/4f French keyboard driver ready + Now what? * - bretjohn, 12.05.2011, 17:13
        int 15/4f French keyboard driver ready + Now what? * - Ninho, 12.05.2011, 22:27
        AMIS, Optimize memory usage - ecm, 13.05.2011, 00:24
        AMIS, Optimize memory usage - Ninho, 13.05.2011, 01:33
        AMIS, Optimize memory usage - ecm, 13.05.2011, 01:45
        AMIS, Optimize memory usage - Ninho, 13.05.2011, 02:07
        AMIS, Optimize memory usage - ecm, 13.05.2011, 02:39
        AMIS, Optimize memory usage - Ninho, 13.05.2011, 02:58
        Correction, memory usage - Ninho, 13.05.2011, 02:50
        Memory usage, AMIS(!) - ecm, 13.05.2011, 03:00
        Memory usage, AMIS(!) - Ninho, 13.05.2011, 11:57
        Memory usage, AMIS(!) - ecm, 13.05.2011, 14:51
        Memory usage, AMIS(!) - bretjohn, 13.05.2011, 17:43
        Memory usage, AMIS(!) - Ninho, 13.05.2011, 18:15
        Memory usage, AMIS(!) - Japheth, 13.05.2011, 18:58
        Memory usage, AMIS(!) - bretjohn, 14.05.2011, 01:42
        Memory usage, AMIS(!) - Ninho, 14.05.2011, 11:38
        Sorry error :) - No contents - Ignore - Ninho, 14.05.2011, 11:41
        Memory usage, AMIS(!) - bretjohn, 15.05.2011, 17:26
        Int15 handler example: IISP; chain other functions directly - ecm, 15.05.2011, 18:30
        Int15 handler example: IISP; chain other functions directly - Ninho, 16.05.2011, 03:49
        Memory usage, AMIS(!) - Ninho, 15.05.2011, 20:57
        In reply to Bret - int 15/4F stuff - Ninho, 16.05.2011, 03:35
        In reply to Bret - int 15/4F stuff - Japheth, 16.05.2011, 10:18
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - Ninho, 16.05.2011, 12:19
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - tom, 16.05.2011, 13:35
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - Ninho, 16.05.2011, 15:10
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - tom, 16.05.2011, 17:13
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - bretjohn, 16.05.2011, 19:50
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - tom, 16.05.2011, 21:06
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - bretjohn, 17.05.2011, 18:10
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - tom, 17.05.2011, 19:47
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - bretjohn, 18.05.2011, 02:09
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - Japheth, 18.05.2011, 06:47
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - bretjohn, 18.05.2011, 19:08
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - tom, 18.05.2011, 12:35
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - bretjohn, 18.05.2011, 18:14
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - tom, 19.05.2011, 15:32
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - Rugxulo, 19.05.2011, 22:42
        Keyboard, codepages... - Ninho, 19.05.2011, 23:41
        FreeDOS DISPLAY (TSR vs. device driver?) - ecm, 20.05.2011, 14:09
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - Ninho, 19.05.2011, 23:59
        In reply to : Bret 'll have to hate FreeDOS mKEYB, too - tom, 20.05.2011, 00:49
        In reply to Bret... - Ninho, 18.05.2011, 15:41
        DOS IO kernel part hooking Int15.4F ? - ecm, 18.05.2011, 20:35
        DOS IO kernel part hooking Int15.4F ? - Ninho, 18.05.2011, 22:41
        DOS kernel, Int15.4F - ecm, 18.05.2011, 22:48
        In reply to Bret... - tom, 19.05.2011, 15:15
        In reply to \\\ Tom... - Ninho, 19.05.2011, 19:27
        AMIS, Optimize memory usage - Japheth, 13.05.2011, 07:28
        AMIS, Optimize memory usage - Ninho, 13.05.2011, 11:27
        AMIS, No flaming - ecm, 13.05.2011, 00:24
        AMIS - ecm, 13.05.2011, 00:24
        AMIS - Ninho, 13.05.2011, 02:21
        AMIS, Ciriaco - ecm, 13.05.2011, 03:23
        AMIS, Ciriaco, Ralph ? - Ninho, 13.05.2011, 12:16
      - int 15/4f French keyboard driver ready + Now what? * - Rugxulo, 11.05.2011, 20:12
        int 15/4f French keyboard driver ready + Now what? * - Ninho, 12.05.2011, 10:36