The study of complex-valued functions in general, and analytic functions in particular, is one of the most researched of the classical fields. Analysis of the geometric characteristics of these functions is a core area of research in this field, however, a paradigm shift in this research is the application of operators, both differential and integral. The impact of any such operator on the geometry of analytic functions is remarkable and of great interest. A huge amount of research is published on the study of operators of both real and complex variables, and it is increasing with every passing year.

The study of operators in complex variables first drew the attention of researchers when Stephan Ruscheweyh introduced a differential operator in 1975. Even today, this operator is one of the most studied and cited, and since its introduction, many versions in the frameworks of different analogues in addition to generalizations have also been introduced and studied in detail. Thus began the new era of functional analysis in complex variables. Operator theory is incomplete without the involvement of integral operators, and as in the differential category, Ruscheweyh gave a breakthrough by defining an operator, whereas R. J. Libera had introduced an integral operator in 1965 that remained the center of research activity until it was generalized by S. D. Bernardi in 1969. This development attracted the attention of numerous researchers, as a result of which several integral operators have been introduced and studied for many kinds of complex valued functions. In the same stream of innovative research, the use of complex versions of many special functions, such as Bessel functions, hyper-geometric functions, Struve functions, Mittag-Leffler functions, and Wright functions, in the formation of integral operators has made them more viable and applicable to the theory of functional analysis.

The aim of this Special Issue is to present recent developments in the theory of functions and operators of complex variables. Original research extendable for future investigation, as well as review articles, are both welcome.

Potential topics include but are not limited to the following:

• Functions of complex variables
• Differential operators
• Integral operators
• Fractional derivative operators
• Q-derivative operators
• Q-analogues of differential operators
• Q-analogues of integral operators
• Differential equations in complex variables