How does industrial programming catalog all the functions, objects, and methods that a project has?

Question

Cataloging

Here is a project, it is being done, for example, by 10-15 programmers.
There are about 500 files in the project folder.
It is clear that not a single person remembers by heart which features have already been implemented where and what they are called, so as not to reinvent the wheel.
Plus, new people come to the project - how do they explain the structure of the project (full-length poster or something)?
In the finished program, the user is provided with help (for example, in the MS Excel volume on functions).
In serious offices with the right approach to design / programming - everyone enters their own function with a description in some local help system or there are some forms of automation of this process (such as something wool all files, and the file has some kind of annotation at the beginning - this is how it is compiled a certain catalog and every programmer, before inventing a bicycle, must first see what is already there from the finished one).
The question was born when I saw a list of files for a "real price" project. One of its developers says that no one remembers anything, of course, and of course, he can reinvent the wheel several times - he doesn't give a damn, as long as it works. Is it really so????

Answer 1

The secret is that people's memory is not permanent and no matter what - the code of the Enterprise project or the smell of grandmother's porridge. We forget everything. In normal organizations there is documentation (like confluence), there are texts (at least Unit), there is automation (deployment scripts, Jenkins, .... ), there are repositories with basic information (README.md in git, at least), there are diagrams ( Visio, Lucidchart, ...) and much more.
Well, do not forget about the documentation in the code and the normal Framework with a standard file structure