What was used before APIs became the standard?

Question

I’m not in the IT sector but I’m beginning to understand the logic behind sending requests and receiving responses for various reasons. What was used before APIs became the standard for communication between systems?

Edit: I understand now that I’ve been in fact asking about REST API.

In: Technology

Answer 1

CSV files FTP’d to a shared place to pick them up and import.

This is often still done because it’s cheap and easy and doesn’t require both teams to be using the same APIs.