

It’s a still frame from Star Trek The Next Generation, episode The Game
The plot is a wearable device that is an AR “glasses” game that as you play the game it “makes you feel good” gets used to take over the Enterprise so terrorists can hijack it.
At the time I imagine it was intended to be part of anti-drug campaigns with the AR and companies curating what you see to distract from reality angle/sentiment being more relevant today
You don’t. In C everything gets referenced by a symbol during the link stage of compilation. Libraries ultimately get treated like your source code during compilation and all items land in a symbol table. Two items with the same name result in a link failure and compilation aborts. So a library and a program with main is no bueno.
When Linux loads an executable they basically look at the program’s symbol table and search for “main” then start executing at that point
Windows behaves mostly the same way, as does MacOS. Most RTOS’s have their own special way of doing things, bare metal you’re at the mercy of your CPU vendor. The C standard specifies that “main” is the special symbol we all just happen to use