Special functions are frequently used in monographs and papers dealing with wave optics. In spite of that they are not involved in the curricula (e. g. the Lommel functions of two variables or the Fresnel integrals). In some cases a mathematical literature does not exist at all (e. g. the Zernike polynomials). Most of the graduates from the technological universities never studied special functions, not even the standard ones (e. g. the Bessel functions). Therefore, the post-graduate students of optical engineering have troubles with the study of books and papers, with mathematical treatment of their own results, and with numerical calculations. The present course offers an overview of mathematics used in wave optics. The exposition is kept in frames of functions of real variables and applications are emphasized.