The familiar beep at the grocery store checkout is so ubiquitous that it has become entirely invisible to us. Yet, prior to 1974, every single item in a supermarket had to be individually marked with a price tag and manually keyed into a register, creating staggering logistical bottlenecks and massive inventory errors. The solution required an engineering miracle that bridged the gap between physical objects and digital data. The invention of the Universal Product Code (UPC) and the laser scanner wasn't just a retail convenience; it was a Trojan horse that completely revolutionized global supply chains, enabling the massive superstores and globalized shipping networks we rely on today. Lines of Control tells the thrilling history of the barcode's creation. It details the intense corporate battles, the engineering failures, and the brilliant mathematical simplicity that allowed a series of black lines to conquer the world and digitize physical commerce. Discover the fascinating story behind the world's most ubiquitous symbol. Understand how the barcode eliminated friction, empowered retail giants like Walmart, and laid the precise mathematical foundation for the modern consumer economy.