How Microsoft Ensured Windows 95 Compatibility with a Bold Software Testing Strategy

In the mid-1990s, as Microsoft prepared to launch Windows 95, ensuring compatibility with existing software was paramount. This commitment led to an unconventional testing strategy that not only underscored the company's dedication but also resulted in an unexpected incident at a local software store.
The Unconventional Testing Strategy
To guarantee that Windows 95 would seamlessly run a vast array of third-party applications, Microsoft's development manager took a hands-on approach. He visited an Egghead Software store—a prominent software retailer at the time—and purchased one copy of every PC program available. This massive acquisition aimed to create a comprehensive testing environment back at Microsoft headquarters.
The Cash Register Incident
The sheer volume of the purchase led to an unforeseen problem. The store's cash register system was not designed to handle transactions exceeding $10,000. As Raymond Chen, a veteran Microsoft engineer, recounted:

"The presumption was that anyone who wanted to buy products exceeding $10,000 would use a purchase order instead." (devblogs.microsoft.com)

When the total surpassed this limit, the register system froze, unable to process the transaction. To circumvent this, the purchase was divided into smaller transactions, each below the $10,000 threshold, allowing the sale to proceed.
In-House Testing at Microsoft
Once the software was transported to Microsoft's campus, it was laid out in the cafeteria. Developers were invited to select up to two programs each, install them on Windows 95, and use them as typical end-users would. They were tasked with identifying and reporting any compatibility issues. Chen described the scene:

"The cafeteria was filled with Windows 95 team members, browsing through the boxes upon boxes of software like bargain hunters at a flea market." (devblogs.microsoft.com)

Developers who effectively ensured compatibility for their chosen programs were allowed to keep them post-launch. This incentive motivated thorough testing and fostered a sense of ownership among the team.
Broader Implications for Compatibility
This incident highlights Microsoft's broader commitment to backward compatibility. The company went to great lengths to ensure that popular applications, even those with inherent bugs, would function on Windows 95. For instance, the game SimCity had a bug where it accessed memory that had been freed. Microsoft identified this issue and implemented specific code in Windows 95 to accommodate it:

"If it finds SimCity running, it runs the memory allocator in a special mode that doesn’t free memory right away." (arstechnica.com)

Such meticulous attention to compatibility was crucial in encouraging users to upgrade to Windows 95 without fear of losing access to their favorite applications.
The Legacy of Egghead Software
Egghead Software, the store involved in this incident, was a significant player in the software retail market during the 1980s and 1990s. Founded in 1984, it expanded rapidly, offering a wide range of software products. However, by the late 1990s, the company faced financial difficulties, eventually filing for bankruptcy in 2001. Its domain name was later acquired by Amazon.com. (en.wikipedia.org)
Conclusion
The story of Microsoft's bulk software purchase and the ensuing cash register crash is more than just an amusing anecdote. It exemplifies the company's unwavering commitment to ensuring Windows 95's compatibility with existing software—a commitment that played a pivotal role in the operating system's widespread adoption and success.

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Source: Windows Report Windows 95 Testing Once Broke a Store's Cash Register — Here’s Why