Imagine a world where every order, invoice, and shipping notice had to be printed, put in an envelope, and mailed — only to be typed into another computer at the other end. That was the slow, mistake‑filled reality before Electronic Data Interchange (EDI). In this chapter, we’ll see how EDI replaced paper shuffling with fast, accurate, computer‑to‑computer document exchange, and why it’s still the quiet engine of modern supply chains.