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DOS-like OS for Intel 8086 / NEC V30
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Nero 7dec8b6c81 Use nasm compat file to allow custom asm variant 
(I dont want to re-implement all those nasm features later)
 		2019-10-14 21:04:42 +00:00
boot Remove misplaced data 2019-10-12 15:10:19 +00:00
debug Rename printf file for more consistent naming 2019-09-20 23:39:57 +00:00
kernel WIP on fcb io 2019-10-14 17:59:48 +00:00
lib Use nasm compat file to allow custom asm variant 2019-10-14 21:04:42 +00:00
programs Advance work on emulator/assembler combo 2019-10-04 21:54:10 +00:00
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.gitignore Ignore emul binary in the future 2019-10-03 17:01:42 +00:00
Makefile Use nasm compat file to allow custom asm variant 2019-10-14 21:04:42 +00:00
README.md Cosmetic changes for README 2019-10-08 10:24:36 +00:00

README.md

Memory Layout

On a 8080, there are no segments, the addresses are as displayed.

On on the 8086, a single segment with a value of 0x0100 is assumed. This implies that the first 4k of memory are not used.

The BDOS may be recompiled for starting at a lower address, in this case, the minimum memory requirement may be less than 64k.

Start Size Function
0xF000 4k BDOS and hw drivers
var BDOS data
SP var Stack, growing down
Free memory
0x0100 up to stack Transient Program Area
0x0080 128 bytes Command line and disk buffer
0x0000 128 bytes System data area

Application program interface

It is using the call 5 convention with CP/M compatible syscall numbers.

File I/O is done via FCB blocks.