The paper describes the features of the DISNEL package for interactive solution of a wide range of discrete and nonlinear optimization problems on compatible models of ES computers (ES-1022 and higher) under ES/OS (version 6.1 and higher) or BOS SVM. The package was developed at the Glushkov Institute of Cybernetics of the Ukrainian Academy of Sciences. It is an improvement over two earlier packages of the same family: DISPRO (discrete optimization) and PLANER (nonlinear programming). In addition to solving the standard ILP and mixed ILP, the package also solves one-parameter linear discrete models and different types of location and extremal combinatorial problems. For these problems, special-purpose (rather than general) methods have been developed. The package also includes modules for solving nonlinear programs, including those that rely on nonsmooth techniques. The general nonlinear program is solved by a method of \textit{B. N. Pshenichnyi} [The linearization method (1983; Zbl 0533.49024)]; convex programs do not assume differentiability of functions and are solved by a generalized gradient method of the third author [Minimization methods for nondifferentiable functions and their applications (1979; Zbl 0524.49002)]. Among special features, two extremal-volume ellipsoids can be constructed by solving convex programs of a special form.