readme.txt

Flat Assembler (FASM) for TRDOS 386

TRDOS 386 adaptation/port of Tomasz Grysztar's Flat Assembler (v1.73.32)

.. FASM.PRG assembles itself ..

NOTE:
 .PRG files are TRDOS 386 (32 bit, x86) flat binary executables.
 They start at virtual address 0 always.
 (Similar to 16 bit MSDOS .COM files  which start at 100h.)
 TRDOS 386 does not use segments. 
 (Demand Paging method is used. The kernel page directory is set
  for 1 to 1 physical memory layout. Interrupts are set to run
  in the 1st 4MB -PDE 0- also with user's page directories.
  User's segment selectors are set for 4MB base address with 4GB-4MB limit.)

(TRDOS 386 kernel handles memory as virtually -up to 4GB- flat memory
 by using system and user page tables.)

((In fact, TRDOS 386 programs start at 4MB physical base address
 but their page directories are set to provide virtual address 0
 as start address. Maximum usable -virtual- memory for TRDOS 386 programs
 is 4GB-4MB.)

How FASM assembles a TRDOS 386 binary:
The answer is 'It is very easy!'.

fasm example.asm -> creates EXAMPLE.BIN file 
    (it will be able to run just after renaming it as EXAMPLE.PRG file)
fasm example.asm example.prg -> creates EXAMPLE.PRG file.

Operating system depended files:
 FASM.ASM, SYSTEM.INC (other files are common source code files of FASM.)

Question: 
  By using FASM.PRG in TRDOS 386 environment...
  Is it possible to assemble executable files
     for WINDOWS, LINUX, DOS or another operating system?

Answer:
  Yes. Just as FASM.EXE and Linux FASM do it.

Erdogan Tan - October 2024