Tibor RadÃ³ proposed a problem of finding which of these objects with some input takes the maximum number of (*) steps in the busy beaver problem.
IIn the MalamentÂ–Hogarth spacetime, one of these objects works for all eternity, but through relativity, an observer can see its results at any point. Roger Penrose discussed a two-dimensional variant of these objects that accepts the same set of all languages as their one-dimensional variants. Tibor RadÃ³ proposed a problem of finding which of these objects with some input takes the maximum number of (*) steps in the busy beaver problem. The fact that it is impossible to devise an algorithm to see if one of these constructs will finish running on an arbitrary input is called the halting problem. These objects have heads that are capable of reading and writing symbols on an infinite tape. For 10 points, name these abstract computational devices named for a British computer scientist.
IIn the MalamentÂ–Hogarth spacetime, one of these objects works for all eternity, but through relativity, an observer can see its results at any point.
Turing machines 