Masm 64

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Here you will find 32 and 64 bit assembly code examples to help you get going with NASM on Windows. Notes, code comments and full assembling and linking instructions are given. The target audience for these examples are those already familiar with x86 and x64, and are looking to switch from a different assembler, such as MASM.

MASM contains a macro language that has features such as looping, arithmetic, and text string processing. MASM also gives you greater control over the hardware because it supports the instruction sets of the 386, 486, and Pentium processors. By using MASM, you also can reduce time and memory overhead. In This Section. ML and ML64 command-line. For MASM-related samples, download the Compiler samples from Visual C Samples and Related Documentation for Visual Studio 2010. The following example demonstrates the use of the.MODEL directive. Example; file simple.asm; For x86 (32-bit), assemble with debug information:; ml -c -Zi simple.asm; For x64 (64-bit), assemble with debug information:; ml64 -c -DX64 -Zi simple.asm. MASM will choose the most efficient encoding for a given size.ALLOCSTACK allows ml64.exe users to specify how a frame function unwinds and is only allowed within the prologue, which extends from the PROC FRAME declaration to the.ENDPROLOG directive. These directives do not generate code; they only generate.xdata and.pdata.A.

Microsoft Macro Assembler
Initial release1981; 39 years ago
Stable release
Operating systemMicrosoft Windows and MS-DOS

The Microsoft Macro Assembler (MASM) is an x86assembler that uses the Intel syntax for MS-DOS and Microsoft Windows. Beginning with MASM 8.0, there are two versions of the assembler: One for 16-bit & 32-bit assembly sources, and another (ML64) for 64-bit sources only.

MASM is maintained by Microsoft, but since version 6.12 it has not been sold as a separate product. It is instead supplied with various Microsoft SDKs and C compilers. Recent versions of MASM are included with Microsoft Visual Studio.


The earliest versions of MASM date back to 1981.[1] They were sold either as the generic 'Microsoft Macro Assembler' for all x86 machines or as the OEM version specifically for IBM PCs. By Version 4.0, the IBM release was dropped. Up to Version 3.0, MASM was also bundled with a smaller companion assembler, ASM.EXE. This was intended for PCs with only 64k of memory and lacked some features of the full MASM, such as the ability to use code macros.


MS-DOS versions up to 4.x included Microsoft's LINK utility, which was designed to convert intermediate OBJ files generated by MASM and other compilers; however, as users who did not program had no use of the utility, it was moved to their compiler packages.

Version 4.0 added support for 286 instructions and also shorthand mnemonics for segment descriptors (.code, .data, etc.). Version 5.0 supported 386 instructions, but it could still only generate real mode executables.

Through version 5.0, MASM was available as an MS-DOS application only. Versions 5.1 and 6.0 were available as both MS-DOS and OS/2 applications.[2]

Version 6.0, released in 1992, added parameter passing with 'invoke' and some other high level-like constructs, in addition to the already existing high level-like records, among other things. By the end of the year, version 6.1A updated the memory management[how?][clarification needed] to be compatible with code produced by Visual C++. In 1993 full support for protected mode 32-bit applications and the Pentium instruction set was added. The MASM binary at that time was shipped as a 'bi-modal' DOS-extended binary (using the Phar Lap TNT DOS extender).

Versions 6.12 to 6.14 were implemented as patches for version 6.11. These patches changed the type of the binary to native PE format. Version 6.11 is the last version of MASM that will run under MS-DOS.

By the end of 1997, MASM fully supported Windows 95 and included some AMD-specific instructions.[3]

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In 1999, Intel released macros for SIMD and MMX instructions, which were shortly thereafter supported natively by MASM. With the 6.15 release in 2000, Microsoft discontinued support for MASM as a separate product, instead subsuming it into the Visual Studio toolset. Though it was still compatible with Windows 98, current versions of Visual Studio were not.[3] Support for 64-bit processors was not added until the release of Visual Studio 2005, with MASM 8.0.


Masm 64 Tutorials

After 25 June 2015, there are at least three different MASMs with the version number 14.00.23026. In Microsoft Visual Studio 2015 Enterprise Edition, there is one 'amd64_x86' ml and two ml64s, 'x86_amd64' and 'amd64'. They run on different platforms targeting different platforms:

  • amd64_x86: generates 64-bit code, runs in a Windows 32-bit environment
  • x86_amd64: generates 32-bit code, runs in a Windows 64-bit environment
  • amd64: generates 64-bit code, runs in a Windows 64-bit environment

Object module formats supported by MASM[edit]

Early versions of MASM generated object modules using the OMF format, which was used to create binaries for MS-DOS or OS/2.

Since version 6.1, MASM is able to produce object modules in the Portable Executable[4][5] (PE/COFF) format. PE/COFF is compatible with recent Microsoft C compilers, and object modules produced by either MASM or the C compiler can be routinely intermixed and linked into Win32 and Win64 binaries.

Assemblers compatible with MASM[edit]

Some other assemblers can assemble most code written for MASM, with the exception of more complex macros.

  • Turbo Assembler (TASM) developed by Borland, later owned by Embarcadero, last updated in 2002, but still supplied with C++Builder and RAD Studio.
  • JWASM Macro Assembler, licensed under the Sybase Open Watcom EULA.
  • Pelle's Macro Assembler, a component of the Pelles C development environment.
  • UASM is a free MASM-compatible assembler based on JWasm.

Masm 64 Tutorial

Mixed language programming support[edit]


Documentation for 1987's version 5.1 included support for 'Microsoft BASIC, C, FORTRAN, Pascal.'[6]

Licensing issues[edit]

Using MASM for operating system development is not prohibited in the license agreement although you may sometimes hear that. This is because people often confuse the MASM and MASM32 licenses; they are two unrelated projects.

See also[edit]


  1. ^Watt, Peggy; Christine McGeever (January 7, 1985). 'Macintosh Vs. IBM PC At One Year'. InfoWorld. Vol. 7 no. 1. pp. 15–16. ISSN0199-6649. The IBM PC Macro Assembler was released in December 1981.
  2. ^Marshall, Martin (April 29, 1991). 'Macro Assembler Update Adds High-Level Features'. InfoWorld. Vol. 13 no. 17. p. 21. ISSN0199-6649.
  3. ^ abR. E. Harvey (2007). 'Assemblers'. Archived from the original on 16 February 2008. Retrieved 4 February 2010.
  4. ^'Archived copy'. Archived from the original on 2009-01-26. Retrieved 2008-06-24.CS1 maint: archived copy as title (link)
  5. ^'WHDC White Papers and Documentation'. Retrieved 25 September 2016.
  6. ^Microsoft Macro Assembler 5.1, Mixed-Language Programming Guide. p. 3.

External links[edit]

Masm 64 bit example
Retrieved from ''


These instructions assume that you have Winzip.exe installed on your PC. If not, download and install it.

Now download into some folder, and then navigate to it using Windows Explorer and double click on it.

This should bring up Winzip, and after agreeing to its conditions, click on 'Extract'. In the window this brings up, alter the 'Extract to' field displayed to 'c:masm615', and ensure that the option 'use filenames' is checked. Now click on the 'Extract' in this window, and close Winzip. This should result in the folder 'cmasm615' being created, with subfolders including 'bin' and 'programs'.

Next click on Start/settings/control panel. Then double click on 'System', select the 'Advanced' tab, and click on 'Environment Variables'. In the lower text box, select 'path', and click on the Edit button below that. Add onto the righthand end of the text which is then displayed above in 'variable value', a semicolon and then: c:masm615bin
After this, close all programs.

Now employ Start/run and type into the box: cmd
and press OK. Maximize the resulting DOS window.
Employ: cd masm615programs
This will make 'programs' the active directory. You should place all the Assembler programs that you create in this folder. The folder already contains a simple program called 'double.asm', which doubles small numbers. Compile this program using: ml double.asm
This should produce an executable called 'double.exe'.
At the command prompt, type: double
and, if everything up to this stage works, the program should ask you to enter a number less than 5.