  Software systems are getting more complex as the system grows where
maintaining such system is a primary concern for the industry. Code clone is
one of the factors making software maintenance more difficult. It is a process
of replicating code blocks by copy-and-paste that is common in software
development. In the beginning stage of the project, developers find it easy and
time consuming though it has crucial drawbacks in the long run. There are two
types of researchers where some researchers think clones lead to additional
changes during maintenance phase, in later stage increase the overall
maintenance effort. On the other hand, some researchers think that cloned codes
are more stable than non cloned codes. In this study, we discussed Code Clones
and different ideas, methods, clone detection tools, related research on code
clone, case study.
