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flat assembler > OS Construction > Help to write driver to write into console in real mode

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Fulgurance



Joined: 27 Nov 2017
Posts: 62
Hello, just for training, i try to write simple driver he have role to write text into console on real mode.

But i have problem, i need to do MOV TARGET,SOURCE instruction with calculated variables adress for target and source. How is it possible to do that. I try many idea, but i don't have any success to compile. (Without interrupt)
Post 20 Dec 2018, 22:35
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bitRAKE



Joined: 21 Jul 2003
Posts: 2784
Location: dank orb
If you can calculate the addresses then the general solution is a PUSH/POP. In the rare case you don't have a stack, you'll need to store the value in a temporary register or memory space.
Post 20 Dec 2018, 23:29
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 16661
Location: In your JS exploiting you and your system
Fulgurance, do you mean computing the address of the characters on the text mode screen?

Something like this:
address = (y * 80 + x) * 2 + base
Where x and y are the coordinates of the character and the "* 2" is for two bytes per character, with the final "base" being the screen buffer start address.

To do that in code you need to write a sequence of instructions with intermediate values. It can't be done with a single "mov [(y * 80 + x) * 2 + base],character".
Post 21 Dec 2018, 01:31
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