How to use the Microsoft® Assembler
MASM (ml.exe) and LINK.EXE
to compile your Assembly
Language Source Code

Copyright © 2004 by Daniel B. Sedory
NOT to be reproduced in any form without Permission of the Author!

The following links are due to the work of Jon Kirwan [Note: Jon's site no longer exists, but this is a link to an archive of his page!] who has done an excellent job in keeping us informed about MASM and related software! I've tried to simplify here how most Windows® users can obtain and install MASM on their system. If you need a purely MS-DOS (16-bit) version of MASM, then take the link above to [the archive of] Jon Kirwan's page! Thankfully, there are still others online (even in 2023) who want to work with such old tools and write about them. One such website is called: The OS/2 Museum; run by Michal Necasek. Don't let the title put you off, there are plenty of discussions about early DOS there!

On Microsoft®'s Visual C++ 6.0 Processor Pack Download page [another page which no longer exists!], there are links to an SP4 or SP5 update which are publically available for download. Both the SP4 and SP5 files contain the same version (6.15) of MASM (ML.EXE) and its associated Error file (ML.ERR). V.6.15 will only work in a DOS (Command-line) box under Windows®, but this is good news for many Windows® users; especially if you are using Windows™ 2000/XP/2003, but still want to learn how to compile a PC (x86) Assembly program.

Steps to Extract/Install MASM Files

1) Download either   SP4 (vcpp.exe; 1160 KiB) or SP5 (vcpp5.exe; 1154 KiB). [I no longer have a link for these at this time.]
You do not need both! Each link has exactly the same files we need to run MASM.

2) If you can extract files from within a Microsoft .CAB file (see #4 below), then change the file extension from .exe to .CAB and proceed to #3. (First, read the "NOTE:"* below.)
    If you'd rather extract every single file from SP4 or SP5 (without using a .CAB extraction program) and read the EULA, then skip #3 below and enter the following command in a DOS box at the directory where you've stored the SP4 or SP5 file, C:\TEMP for example:
    C:\TEMP>vcpp5 /c /t:C:\MASM615
(the "/c" command means it will "Extract files only" when also used with the "/t:<full path>" command which specifies the location).
   Before proceeding to step #5, read through step #4 so you know which files are actually necessary to run MASM; most of them will have nothing to do with it!

*NOTE: The EULA implies that you should have a licensed version of either "Visual Studio" or "Visual C++" (something you would definitely need to have if you wanted to legally sell a "commercial" program using MASM!). However, the letters that Jon Kirwan exchanged with a Microsoft employee (see link above) seem to imply that Microsoft wants to encourage academic (personal?) use of MASM so long as you do not go to them with 'support questions' without a valid license. If you feel a need to pursue this any further, you'll have to go to Microsoft (and/or others) for answers.

3) Create a directory for MASM, such as C:\MASM615.

4) Use your favorite .CAB tool, such as
WinZip (demo available) which can extract files from .CAB archives, to extract only the following files to the directory you just created:
        385,072 bytes  03/16/2000 04:20p
    ml.err               9,687 bytes  03/16/2000 04:20p
[ Although Windows™ XP/2003 can work with .zip archives, it appears you cannot extract individual files from .CAB archives using only the OS. Does anyone know of a free .CAB extraction tool? ]
    MasmRef.doc (513,536 bytes; 08/09/2000, 2:28 PM), will also be helpful to you; feel free to look through "procpack.chm" as well, though its mostly for professional programmers.
Although they're not really necessary, you might as well grab these next two files:
    h2inc.exe    249,344 bytes  09/19/1995 02:04p
    h2inc.err        21,880 bytes  09/19/1995 02:04p
'h2inc' allows you to convert C language include files into assembly include files; we've never used it, but you might find a need for it some day.

Download the file, LNK563.EXE, from either here: HTTP site or here: FTP site [Note: Neither of those Microsoft links work anymore either.] into your MASM directory.

You can either open this self-extracting file (LNK563.EXE) with a .ZIP tool such as WinZip, or execute it; if you do the latter, delete the README.TXT file which can be very confusing as it refers to this file as a "patch," but these are the full versions of:
         LINK.EXE     364,544 bytes  01/13/1995  02:10p   and
  CVPACK.EXE     169,472 bytes  01/13/1995  02:10p (A CodeView debug information compactor which most of you won't ever have a reason to use, but here it is.)

And that's all there is to it! You're now ready to compile programs from any .asm source code written for MASM. Open a DOS-box (see "Helpful HINT" below) at your MASM directory, and ENTER ml /? > ML.TXT at the prompt. ML.TXT will then contain a simple listing of all the switches you can use with MASM. ENTER ml all by itself, and you should see:

Microsoft (R) Macro Assembler Version 6.15.8803
Copyright (C) Microsoft Corp 1981-2000. All rights reserved.
usage: ML [ options ] filelist [ /link linkoptions]

Helpful HINT: Install the Win2000/XP "Power Toy" that allows you to open a Command-Line (.CMD) window at any folder by simply right-clicking on the folder name in Windows Explorer and selecting "Command Prompt Here" from the menu. You'll probably find a lot more use for .CMD and Batch files after doing this!   Direct Link: (513 KiB). [Note: The Power Calculator is the only other program I'd recommend from this series.  I would not use the TweakUI program!]

At this point, I'd recommend going through a very nice tutorial by Jon Kirwan called: Learn ASM. [Thankfully, all of Jon's examples can still be found here at the website!] It not only covers the basics of using MASM along with some example source code, but includes valuable information on subjects such as the PSP (Program Segment Prefix), the difference between a .COM and .EXE program file, the EXE Header fields at the beginning of all .EXE files plus historical background you'd rarely find in most tutorials.

Once you've done that, go ahead and download the following .asm source code which will teach you a bit more about Assembly code under MASM: DOSWIN.ASM. (Download to your MASM directory and follow the instructions inside the file.) After compiling and running the program, you should open it under DEBUG and step through each instruction until you have understood what each of them do!

In one of the paragraphs above, I mentioned that you can now compile .asm source code "written for MASM." This refers to the fact that souce code written for other assemblers, such as Borland®'s Turbo Assembler (TASM) which we also consider to be quite good, may use Macro statements which MASM has no idea how to understand, and vice versa. Note that the command-line switches used by a particular assembler often have a completely different function under that of another! A seasoned x86 programmer will most likely have learned how to translate the source code for one to the other (or be able to slog through it) out of necessity, needing to implement some code snippets found only for one in a project using another assembler. Sooner or later, you'll need to consult the manuals which describe all the special directives you can use under each assembler. For now though, you should concentrate on learning the basic Assembly mnemonics used by all of them.


Last Update: 26 JAN 2005. (26.01.2005)

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