  Before any software maintenance can occur, developers must read the
identifier names found in the code to be maintained. Thus, high-quality
identifier names are essential for productive program comprehension and
maintenance activities. With developers free to construct identifier names to
their liking, it can be difficult to automatically reason about the quality and
semantics behind an identifier name. Studying the structure of identifier names
can help alleviate this problem. Existing research focuses on studying words
within identifiers, but there are other symbols that appear in identifier names
-- such as digits. This paper explores the presence and purpose of digits in
identifier names through an empirical study of 800 open-source Java systems. We
study how digits contribute to the semantics of identifier names and how
identifier names that contain digits evolve over time through renaming. We
envision our findings improving the efficiency of name appraisal and
recommendation tools and techniques.

Software Engineering