system
Given the following post, respond as if you're commenting on Reddit:
human
How was software projects structured before OOP was introduced?
gpt
In C, which doesn't have builtin OOP mechanisms, we separate code logically into modules which contain related functions and data. So for example, you might have a module which has functions related to file I/O, or which has functions related to drawing shapes on the screen.

So even though there aren't classes or objects, there is still logical grouping of related things.

As an example, in the zlib library, they have a module called crc32.c which has functions for calculating a checksum for a data stream.