  We consider the most general class of linear boundary-value problems for
ordinary differential systems, of order $r\geq1$, whose solutions belong to the
complex space $C^{(n+r)}$, with $0\leq n\in\mathbb{Z}$. The boundary conditions
can contain derivatives of order $l$, with $r\leq l\leq n+r$, of the solutions.
We obtain a constructive criterion under which the solutions to these problems
are continuous with respect to the parameter in the normed space $C^{(n+r)}$.
We also obtain a two-sided estimate for the degree of convergence of these
solutions.
