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

APIs were first used in the 1940s, pretty much as soon as there was a need for them. As such, there isn’t really a time before APIs for communication between computer systems.

That’s hopefully enough waffle that ELI5 doesn’t delete the post.