A fundamental, unsolvable limitation proven by Alan Turing in 1936.
Shows that no general algorithm can determine whether any arbitrary program will eventually stop (halt) or run forever.
Given a description of a computer program and an input, can you write a program (a “checker”) that decides whether the program will finish running or run forever? It has been mathematically proven that such a general algorithm cannot exist.
Serves as a foundational example of limitations in computing.