The Evolution of Programming Languages in AutoCAD

AutoCAD, a widely used computer-aided design (CAD) software, has been the cornerstone of many engineering and architectural projects. The choice of programming languages over time has significantly influenced the software's evolution. In this article, we explore the journey of programming languages in AutoCAD from its inception to the present day.

Early Beginnings: AutoCAD in C (1991-2000)

My journey at Autodesk began in 1991 when AutoCAD R11 was already on the market, and development was actively working on R12. The development team primarily used C for its robustness and efficiency. Developers often worked on a Sun workstation running Unix (SunOS or Solaris), given the superior interactive symbolic debugging capabilities these environments provided.

The DOS version of AutoCAD was a significant challenge. It was compiled using a WATCOM C compiler with a Phar-Lap DOS extender to enable access to more memory than native DOS compilers could handle. However, the WATCOM compiler lacked a good interactive debugger, which made the Unix environment more preferred for development.

The Transition to Windows (2000-2010)

With the release of Windows NT and the availability of Visual C, AutoCAD development shifted from Unix-based systems to Windows. This transition not only streamlined the development process but also improved the stability and performance of the software.

Simultaneously, the API for creating AutoCAD extensions underwent a significant change. From the Lisp-based AutoCAD Development System (ADS) to the C object-oriented ARX API, the shift was a strategic decision to enhance the software's capabilities and future-proofing.

The ARX API: A Game-Changer

The ARX API, introduced around AutoCAD R13, revolutionized the way developers interacted with AutoCAD. It provided a more structured and object-oriented approach, which was easier to manage and scale. Developers embraced the MFC (Microsoft Foundation Classes) with Windows resource files for menus and dialog boxes, replacing the clunky platform-independent menu and dialog box system used in Unix days.

The introduction of MFC's CString class in AutoCAD code demonstrated the shift towards modern development practices. This transition not only improved development but also enhanced user interaction with the software.

The Continued Use of C and C

Since AutoCAD's transition to Windows, the primary programming language has remained C and C . While C is mostly a superset of C, the combination of both languages allowed for better compatibility and performance. The majority of the older code written in C has been gradually replaced or integrated into the C framework, ensuring a seamless update process.

The Persistent Role of AutoLisp

While C and ARX dominate the primary development, AutoCAD also supports AutoLisp, a Lisp-based programming language. AutoLisp has been a crucial tool for customizing and automating tasks within AutoCAD for decades. The Lisp interpreter in AutoCAD acts as a programming interface, and the AutoCAD command prompt has historically been a disguised Lisp prompt.

The older ADS API, which used a "resbuf" (result buffer) for communications, demonstrated the limitations of such a system. The move to the ARX API was partly motivated by the inefficiencies in handling long linked lists, which were optimized in the ARX system.

Conclusion

The evolution of programming languages in AutoCAD reflects the software's adaptability and commitment to innovation. From the early C-based development on Unix to the current C and ARX API, AutoCAD has continuously evolved to meet the changing needs of its users. The enduring role of AutoLisp underscores the software's flexibility and the importance of supporting diverse programming environments.

As AutoCAD continues to advance, the choice of programming languages will remain a crucial factor in enhancing its features and performance. Developers and users alike can look forward to a future where AutoCAD continues to lead in the CAD industry.