Contemporary instructional approaches expect students to be active producers of knowledge. This leads to the need for creation of instructional tools and tasks that can offer students opportunities for active learning. This study examines the effect of a computational experiment as an instructional tool-for Grade 12 students, using a computer simulation environment created in Java for the domain of "linear oscillations without damping". In this study we use the computational experiment as an integration of the computational science with the discovery learning method. The computational experiment supports both types of research, the exploratory as well as the inventive research, helping the learners to develop not only exploratory but also expressive models. The aim of the paper is threefold. At first we want to examine the influence of the computational experiment on students' learning performance. The other two aims are related to the investigation of the experiment's influence on students' approach to learning and their beliefs on physics. Our results indicate that there is a strong shift on students' conceptual understanding and to the consideration of the coherence of physics, as well as to the realization that physics is strongly connected to mathematics. Finally students realized that mathematics, physics and information theory are strongly connected cognitive disciplines. (Contains 7 tables and 3 figures.)