DOS ain't dead - How to keep resident only a part of the program

How to keep resident only a part of the program (Developers)

posted by Laaca , Czech republic, 08.03.2022, 12:24

I succeeded to solve this problem!
It is possible to create a big program in the Turbopascal and keep only a tiny TSR in the memory and unloaded the rest.
The practical implementation I used here.

The principle is to write a small assembler procedure which will be used as a TSR. In this procedure keep a area which will be modified on the fly to store there some data.
Then move this procedure/module just after PSP of the main program. (PSP+256)
Now is it a little bit dangerous because a part of the pascal system library is overwritten so it is not safe to call many RTL functions.
In assembler redirect the calling interrupt vector to PSP+256
Then call the DOS function 31h and into DX store the 16+TSR_size/16.
And it works :-)

The question is: Do I need to keep the PSP? Is it safe to perform the relocation not to PSP+256 but to PSP+128? Or to PSP+0?

---
DOS-u-akbar!

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Complete thread:

How to keep resident only a part of the program - Laaca, 14.08.2021, 07:31 (Developers)
- How to keep resident only a part of the program - tkchia, 14.08.2021, 08:49
  - How to keep resident only a part of the program - Laaca, 14.08.2021, 10:32
    - How to keep resident only a part of the program - tom, 14.08.2021, 11:40
      - How to keep resident only a part of the program - RayeR, 14.08.2021, 15:49
        How to keep resident only a part of the program - Laaca, 14.08.2021, 20:18
        How to keep resident only a part of the program - RayeR, 16.08.2021, 03:22
  - How to keep resident only a part of the program - tom, 14.08.2021, 11:28
  - How to keep resident only a part of the program - ecm, 15.08.2021, 13:47
    - How to keep resident only a part of the program - bretjohn, 27.08.2021, 21:22
- How to keep resident only a part of the program - marcov, 14.08.2021, 13:18
- How to keep resident only a part of the program - CandyMan, 27.08.2021, 17:46
- How to keep resident only a part of the program - bretjohn, 27.08.2021, 21:47
- How to keep resident only a part of the program - Laaca, 08.03.2022, 12:24
  - How to keep resident only a part of the program - tom, 08.03.2022, 12:51
    - How to keep resident only a part of the program - tkchia, 08.03.2022, 14:20
      - How to keep resident only a part of the program - bretjohn, 08.03.2022, 19:19
  - How to keep resident only a part of the program - rr, 08.03.2022, 17:32