Microsoft releases 6502 BASIC as open source after nearly five decades

Microsoft Unveils Open Source Version of 6502 BASIC

In a landmark move, Microsoft has open-sourced one of its cornerstone products, 6502 BASIC. The complete source code for Microsoft BASIC Version 1.1, intended for the 6502 microprocessor, is now accessible on Microsoft’s GitHub repository, totaling an impressive 6, 955 lines of code.

A Historical Milestone in Computing

6502 BASIC holds a place of significance in computer history, predating Microsoft’s well-known operating systems, MS-DOS and Windows. This software was pivotal during the early days of personal computing, influencing countless developers and shaping programming standards.

Previous Open-Source Initiatives

Before this development, Microsoft had open-sourced the GW-BASIC interpreter in 1983. However, 6502 BASIC’s source code was scarce, lost in time and largely available only in fragmented or unofficial forms circulating on retrocomputing websites and preserved in museum collections.

Technical Insights into 6502 BASIC

Designed for the MOS Technology 6502 8-bit microprocessor, 6502 BASIC is based on the BASIC-80 interpreter for Intel 8080 processors. It supports a comprehensive BASIC implementation, featuring floating-point arithmetic, array manipulation, string management, and input/output operations, which laid the groundwork for later advancements in programming languages.

Impact on Personal Computing

This programming language interpreter introduced millions to personal computing and established itself as the standard for many early computers. Microsoft’s design principles were influential and have been echoed in numerous programming languages and development tools throughout subsequent decades.

Key Developments and Licensing

In 1976, Bill Gates and Ric Weiland completed the porting of 6502 BASIC, which was subsequently licensed to Commodore for a flat fee of $25, 000 in 1977. This transaction facilitated the development of the Commodore BASIC dialect on popular 8-bit models, including the PET, VIC-20, and Commodore 64. Additionally, 6502 BASIC was adapted for the Apple II, known as Applesoft BASIC.

The Open-Sourced Version

As highlighted by Microsoft, the newly open-sourced version includes enhancements to the garbage collector made in collaboration with Commodore engineers in 1978, specifically John Feagans and Bill Gates. During Feagans’ visit to Microsoft’s Bellevue offices, these improvements were collaboratively integrated.

Fun Facts and Easter Eggs

The open-source release comes with a hidden gem: a Bill Gates easter egg embedded in the labels STORDO and STORD0, a nod confirmed by Gates himself in 2010.

Reviving Retro Computing

The revival of 6502 BASIC as open source opens up exciting opportunities for hobbyists, tech historians, and hardware enthusiasts to experiment with this classic language on contemporary platforms. This release aligns with the growing trend of retro computing, inspiring projects that utilize emulators and FPGA-based recreations like the Commodore 64 Ultimate.

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