An asm file is a text file containing
assembly language programming
source code.
Naturally, you can open or read
it with any text editor.
In order to run the program,
it must be run through a programming
tool called an assembler.
The assembler takes it, reads it,
and produces an executable file.
The difficult part is that the asm file is written
not only for a specific type of processor/computer,
but that the way it is written will
also require a specific assembler.
If you are lucky, the person who wrote
the file included comments telling you what
computer, operating system and assembler
the file is written for.
