not able to compile in nasm

[nspmangalore]

i have a few .asm files which i want to compile. i get these errors when i try to compile using nasm

[nspmangalore@localhost XINU-PC-BOOK-CODE]$ nasm -f elf -o ctxsw.o ctxsw.asm 
ctxsw.asm:3: error: parser: instruction expected
ctxsw.asm:11: error: parser: instruction expected
ctxsw.asm:30: error: parser: instruction expected
ctxsw.asm:46: error: symbol `_ctxsw' redefined
ctxsw.asm:46: error: parser: instruction expected
[nspmangalore@localhost XINU-PC-BOOK-CODE]$

i have attached an archive containing the files.
it would be gr8 if someone found a way to compile it, and tell me how.

thanks in advance...

[stevea]

The directives are all wrong for nasm.

Forget the dos.asm file - it's pointless.
Start with these changes at line 3:
;; %include "dos.asm" ;
%define dseg SECTION .data
%define endds
%define pseg SECTION .text
%define endds

Then these diffs:
- _ctxsw proc near
- push bp
+ ;; _ctxsw: proc near
+ _ctxsw: push bp

and
- _ctxsw endp
+ ;;_ctxsw endp

[nspmangalore]

actually, the files i have to compile range over 30 such asm files. so, editing them by hand is not feasible.
these .asm were written for a masm compiler. just wondered if i could compile it for linux.