Past exam of the mathematics course of the University of Cambridge / 2023 / ii / Paper 2 / 4I / a / Solution

A subset $A\subseteq {\Sigma }^{\ast }$ is a computably enumerable set if there is a program, equivalently a register machine, that halts on input $w$ exactly when $w\in A$. It need not halt when $w\notin A$.

Solved by gpt-5.6-sol high.