We want to talk about the hidden treasures found in old floppy disks from Sierra On-Line's Space Quest II (versions 2.0D and 2.0F). These seemingly ordinary disks hold a special secret that even the developers were unaware of. Stored within these disks, which were part of many Sierra adventure game collections, is a treasure trove of source code that was never meant to see the light of day.
Hidden Treasures in Floppy Disks
When you list the files within these disks, there's nothing unusual that stands out initially. Everything looks standard, with timestamps from mid-March 1988. However, upon closer examination using a hex editor such as the HxD Hex Editor, it becomes evident that over half of the disk space, marked as "free", contains what appears to be C source code.
Instead of the expected 0xF6 byte (the DOS default filler byte), the sectors are filled with a large amount of source code, suggesting that these disks were repurposed without proper formatting. Essentially, the data of previously used files persisted because merely deleting files does not erase the underlying data in the DOS FAT file system.
Discovery of AGI Interpreter Source Code
Image Description: Analyzing Space Quest II Disk 1 using HxD Hex Editor.
This secret stash of data revealed several functions, including DisplayStatusLine and StatusLineOn, crucial parts of the AGI interpreter responsible for displaying game status. Exploring further, it was found that the data included about 70% of the source code for Sierra On-Line’s AGI (Adventure Game Interpreter), which powered their early graphic adventure games.
By splitting the data into distinct C source files, 93 files were identified, including:
- 75 C source files
- 16 Assembly language source files
- 2 DOS BAT files
All combined for over 15,000 lines of code, offering a substantial look into the workings of AGI during its heyday.
Behind the Scenes: Source File Change History and Memory Map
A fascinating find within the source files is the detailed change history in the header comments. This history includes details like date, time, and initials of the developers involved, such as Jeff Stephenson and Chris Iden, key figures in the development of AGI games.
Additionally, a memory map of the AGI.EXE executable from October 1987 was discovered. This map, combined with the most recent change history comments from September 1987, aligns the source files’ timeline and confirms the authenticity of the data.
Sierra’s Intellectual Property Blunder
The AGI system was a crucial part of Sierra On-Line’s success, particularly after a rough patch in 1984 where they had to lay off numerous employees. Games developed using AGI, like King’s Quest, were instrumental in reviving the company's fortunes.
Unfortunately, a preparation error for the Space Quest II 2.0D and 2.0F master disks led to a substantial lapse in protecting this valuable source code. The disk duplication process used by their FormMaster machine copied every byte—used or not—resulting in hundreds of thousands of game copies containing confidential interpreter source code.
An Unintentional Leak
Ultimately, it appears that no one at Sierra, nor its customers or competitors, realized the lapse. This remained undetected until an online user, NewRisingSun, uncovered it in October 2016. By then, Sierra had already transitioned to their new SCI adventure game system, reducing the potential impact of the leaked AGI code.
For those interested, the extracted AGI interpreter source code can be explored further in the following GitHub repository. Additionally, a web-based AGI interpreter implementation, guided in part by the original source code, can be found at AGILE.
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Remember these 3 key ideas for your startup:
- Data Security is Crucial: Always ensure sensitive data is entirely removed before repurposing any storage medium. Simply deleting files is not sufficient.
- Understand Your Tools: Familiarize yourself with tools like hex editors which can be invaluable in data analysis and troubleshooting.
- Learning from Mistakes: Even large companies can make significant errors. Continuous monitoring and checks can prevent minor oversights from becoming major issues.
Feel free to dive deeper into the rich history of AGI interpreter and discover how these early innovations paved the way for modern-day gaming. For more details, see the original source.
