I have a piece of code written as:
\begin{lstlisting}
code
\end{lstlisting}
I want to put a box, around the code.
I have already read this question Source code listing with frame around code?
But I only want a simple box, not the title at the beginning

[frame=single]option. (The manual is available usingtexdoc listingsor here: https://ctan.org/pkg/listings?lang=en) – Rmano Mar 16 '21 at 10:50