Name/Title
1985- Microsoft Macro Assembler (MASM) v4.0 (6/2025)Tags
MicrosoftDescription
Microsoft Macro Assembler (MASM) was first introduced in 1981 as an x86 assembler for MS-DOS systems, initially known as MACRO-86 in its earliest form. It was available both as a generic version for all x86 machines and as an OEM-branded edition specifically for IBM PCs (sold as IBM Macro Assembler). Early versions, from 1.0 through 3.0, included a companion lightweight assembler called ASM.EXE, which was optimized for low-memory environments (e.g., 64KB RAM PCs) but lacked advanced features like code macros present in the full MASM. These early releases focused on basic 8086/8088 support and were bundled with utilities like LINK (for linking object files), LIB, and CREF.
Version 4.0, released in 1985, represented a key evolution in MASM's development, aligning with advancements in PC hardware during the mid-1980s. This version dropped the IBM-branded OEM edition, consolidating MASM as a Microsoft-only product. It also discontinued the bundled ASM.EXE companion assembler, signaling a shift toward assuming more capable hardware environments.Acquisition
Acquisition Method
EBayDate
Mar 2025General Notes
Note
Key Features and Changes in Version 4.0:
Processor Support: Added instructions for the Intel 80286 processor, enabling developers to target protected mode and extended memory features introduced with the IBM PC/AT and similar systems.
Syntax Improvements: Introduced shorthand mnemonics for segment descriptors, such as .code and .data, which simplified code organization and made assembly programming more intuitive compared to manual segment definitions in prior versions.
Error Handling Directives: Added several new conditional error directives, including .err1, .err2, .errb, .errdef, and .errdif, enhancing macro debugging and conditional assembly capabilities.
Utilities: Retained Microsoft's LINK utility for converting OBJ files generated by MASM or other compilers, though this would later be separated for non-developer users in subsequent MS-DOS versions.
Version 4.0 was distributed on floppy disks for MS-DOS and retailed as a standalone development tool. It built on the macro language strengths of earlier releases while preparing the groundwork for future expansions, such as the 80386 support added in version 5.0 (released in 1987). MASM 4.0 was part of Microsoft's broader push into professional development tools during the DOS era, and its User's Guide from 1985 documents these enhancements in detail. Overall, this version helped solidify MASM as a leading assembler for PC software development, influencing later iterations that would integrate with Windows and Visual Studio.