What does $\{0 , 1\}^+$ mean?

Question

I'm trying to do an assignment in my theory of computation class, and its talking about some abstract mapping $\sigma$ as defined $\Sigma^+ \mapsto \Sigma^*$. I am familar with what $\Sigma^*$ means, as has already been clarified in this question : What does $\{0, 1\}^*$ mean? , however i am very puzzled by what $\Sigma^+$ refers to. Could anyone help me? Here $\Sigma$ is a set $\{0 , 1\}$

Answer 1

$\Sigma^+$ is by definition $\Sigma\Sigma^*$, so in your case it would be all non-empty strings of 0s and 1s.