  Background: During software maintenance and development, the comprehension of
program code is key to success. High-quality comments can help us better
understand programs, but they're often missing or outmoded in today's programs.
Automatic code summarization is proposed to solve these problems. During the
last decade, huge progress has been made in this field, but there is a lack of
an up-to-date survey. Aims: We studied publications concerning code
summarization in the field of program comprehension to investigate
state-of-the-art approaches. By reading and analyzing relevant articles, we aim
at obtaining a comprehensive understanding of the current status of automatic
code summarization. Method: In this paper, we performed a systematic literature
review over the automatic source code summarization field. Furthermore, we
synthesized the obtained data and investigated different approaches. Results:
We successfully collected and analyzed 41 selected studies from the different
research communities. We exhaustively investigated and described the data
extraction techniques, description generation methods, evaluation methods and
relevant artifacts of those works. Conclusions: Our systematic review provides
an overview of the state of the art, and we also discuss further research
directions. By fully elaborating current approaches in the field, our work
sheds light on future research directions of program comprehension and comment
generation.
