The main range of tasks reduced to the calculation of objects is presented - "from simple to complex." A specific variant of the calculus is selected depending on the computational problems being solved. During the sequential solution of problems, the reader masters the basic methods and means of combinatorial logic and A-calculus. All tasks are provided with detailed and elementary solutions. For senior and graduate students studying the mathematical foundations of object-oriented computing, beginners and professionally working on advanced programming projects. It can be used in courses of discrete mathematics, computer science, programming theory. No prior mathematical training is required. The material can be partially or completely used for independent study as a book "for the first reading."