In mid-1972, an electronic revolution took place. For the first time in electronic history, you could go out and buy a logic gate for a nickel, provided you bought four of them at once in a single 20-cent package. This made the logic gate the cheapest available electronic component—cheaper than most quality resistors and far cheaper than any capacitor, transistor, or most other solid-state devices. These gates were made of Transistor-Transistor-Logic (TTL), a very versatile, widely available, and very fast way of performing logic operations.
The extremely low cost did two things. First and foremost, it opened up a fantastic number of still expanding applications for digital circuitry. At long last, doing things digitally was not only better than using traditional analog circuits, but now it was often cheaper as well. — TTL Cookbook
