What exactly is the halting problem?

Question

Whenever people ask about the halting problem as it pertains to programming, people respond with \"If you just add one loop, you\'ve got the halting program and therefore yo

Answer 1

Here is a simple explanation of the proof that the halting problem is undecidable.

Assume you have a program, H, which computes whether or not a program halts. H takes two parameters, the first is a description of a program, P, and the second is an input, I. H returns true if P halts on input I, and false otherwise.

Now write a program, p2, which takes as it's input the description of another program, p3. p2 calls H(p3, p3), then loops if H returns true and halts otherwise.

What happens when we run p2(p2)?

It must loop and halt at the same time, causing the universe to explode.