Аннотация:Could the complexity of a thing be measured by a number? Is it necessary for the theory of information to be based on the concepts of theory of probability? Is it possible to partition the set of infinite binary strings into two subsets, namely, the subset of random strings and the other of non-random ones? The goal of this paper is to present the answers to the above questions which are provided by the Kolmogorov theory. The basic preliminaries from the theory of computability needed for this paper are listed in the Appendix.