Real applications execution

In order to take actions on packages, we must call the package manager tools. The virtual methods that the PkgManager implementation supplies are straightforward:

• $\texttt{int install(string}$ pkg_name, $\texttt{string}$ options $\texttt{)}$;
• $\texttt{int remove(string}$ pkg_name, $\texttt{string}$ options $\texttt{)}$;
• $\texttt{int update()}$;
• $\texttt{int upgrade()}$.