Which accidental invention from the 1940s was later repurposed for retail use and is now considered the foundation of modern inventory tracking systems?

In the world of inventions and discoveries, some of the most impactful retail innovations happened by complete accident. This poll tests your knowledge about a pivotal retail technology that wasn't initially designed for store use, but revolutionized inventory management and checkout systems worldwide. The story behind this invention demonstrates how scientific curiosity in one field can transform completely unrelated industries.

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Barcode (initially developed as a railroad tracking system before being adapted for supermarket use in the 1970s)
RFID tags (initially developed as spy technology during WWII espionage operations)
Touchscreen displays (originally created for air traffic control systems before retail adoption)
Electronic cash register (first designed as an accounting tool for banks before retail implementation)