This review presents the results of Scenario Machine computations aimed at the population synthesis of different types of binary stars in our Galaxy and another galaxies. They demonstrate the ability of this method to make an important gross analysis of the modern scenarios for binary evolution, as well as to give interesting qualitative and quantitative predictions which can be checked observationally.
Of course, even the last version of the code used in the Scenario Machine, is rather a schematic representation of the evolution of binary systems which in reality is much more complicated. However, even at the present level, the method is obviously indispensable for overall analysis of different evolutionary scenarios, and, hence, for understanding binary stellar evolution as a whole.
The future development of the method can be considered from two different points of view.
First, this is the amendment of the method itself in the sense of more adequate and detailed description of stellar evolutionary tracks (as performed by, e.g., Pols and Marinus (1994)). In fact, this is indeed necessary for some classes of objects (for instance, if we investigate in detail a particular type of object, e.g. cataclysmic variable, their distributions over masses, orbital periods, etc.). However, here one should always bear in mind that various uncertainties of the modern evolutionary scenario (such as adequate description of the common envelope stage, Roche lobe overflow process, parameters of the magnetic stellar wind, etc.), could hardly make the detailed calculations more precise than they are already (i.e. they do remain uncertain to within the same factor of 2).
On the other hand, as the 10-years history of the Scenario Machine shows (see particularly the last few sections of this review), interesting results (and more statistically reliable) can be obtained by applying Scenario Machine methods to various examples of extragalactic binary systems evolution. That is, it may be better to refer not to the evolution of stars, but to evolution of the baryonic component of the Universe.
One important feature revealed by our computations is that practically all populations of stars in galaxies are very sensitive to the previous star formation history. In this connection, a more accurate account of the relevant chemical evolution is urgently needed, and this is what we are going to do in the near future.