A86 Assembler Compiler-specific extensions

23 Sep 2023

The A86 Assembler is a powerful tool for compiling assembly language code into machine code. In addition to supporting standard assembly language syntax, A86 also provides some compiler-specific extensions that can enhance the development process and improve code efficiency.

Macro Expansion

One of the standout features of A86 is its support for macro expansion. Macros allow you to define reusable code fragments, which are then expanded inline during assembly. This helps in reducing code duplication and improves code readability.

To define a macro, use the MACRO directive followed by a unique identifier. Inside the macro, you can write regular assembly language instructions. To invoke the macro, use the identifier followed by any necessary arguments.

; Define a macro to add two numbers
MY_ADD MACRO a, b
    MOV AX, a
    ADD AX, b
ENDM

; Invoke the macro
MY_ADD 5, 10

During assembly, the MY_ADD macro will be expanded to the corresponding instructions, effectively adding 5 and 10 together.

Segmented Memory Model

A86 also introduces a segmented memory model that allows you to work with larger memory spaces. This model extends the 16-bit addressing capabilities of the x86 architecture.

To enable the segmented memory model, use the CGROUP directive, followed by the segment size in bytes (power of 2) and the maximum segment number.

; Enable segmented memory model with 64KB segments
CGROUP 64K

This directive ensures that memory accesses are properly handled within the defined segments. You can then use segment registers (CS, DS, ES, SS) to address different segments of memory.

Conclusion

The A86 Assembler not only supports standard assembly language syntax but also offers specific extensions that can greatly enhance code development and efficiency. With its macro expansion feature, you can write reusable code fragments and reduce code duplication. Additionally, the segmented memory model allows you to work with larger memory spaces, efficiently utilizing the full power of the x86 architecture.

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