How do I compile more than one .asm file with fasm into one output?

Question

I want to compile multiple assembly files in fasm. I have some instructions in the one file and other instructions in the other file. How do I link these files to a binary output ?

And may I use extern in this case ? Or is this an illegal command ?

Answer 1

I want to compile multiple assembly files in fasm.

So you have multiple .ASM source files.

• Select one of your source files as the main source file.
• Insert in it an include preprocessor directive for every additional source file that you want in your single binary output file.
• Assemble. No linker required, FASM does it all.

Example with 3 source files

; Main source is 'source1.asm'
include 'source2.asm'
include 'source3.asm'
...

Answer 2

I generally create an includes file (much like a header for my application) and simply include that file which lists all files to be "included".

include 'includes.inc'

The includes.inc will then, itself, have all the relevant inclusions listed for a "project style" structure.

This is an alternative approach to what Fifoernik states (which is correct).

I also like to externalize data segments as well (especially when developing for Windows) into vars.inc (read & write permissions, no execution) and const.inc (read only with no write or execution permissions). Something else to ponder on a side note.