Abstract: Clone code is duplicate or similar code fragment. These duplicate codes from the “copy and paste modification” of programming, such codes are believed to reduce the maintainability of software severely. The existence, development and change rule of clone code are explored from various perspectives. Clone code is traced and found the characteristics and patterns of performance in the evolution process, so as to better research and management, and clone mapping is the key step of the whole research process. In this paper, several different types of mapping methods are introduced, the advantages and disadvantages of various mapping methods are summarized, and the application of the clone mapping in clone evolution analysis and clone quality evaluation is described; the development trend of clone mapping is summarized and prospected.

Key words:  code clone, clone mapping, software maintenance, clone evolution, clone quality

摘要： 克隆代码是指重复或类似的代码片段，这些重复代码来自于“复制粘贴修改”的编程方式，此类代码会严重影响软件的可维护性。研究者们从各种角度来探索克隆代码的存在、发展和变化规律，对克隆代码进行追踪并发现在其演化过程中表现的特征和模式，从而更好地研究和管理，而克隆映射是整个研究过程的核心步骤。介绍了克隆相关概念及术语，详细阐述了不同类型的映射方法并总结方法的优缺点，说明了克隆映射在克隆演化分析和克隆质量评估方面的应用，对克隆映射的发展趋势进行了总结和展望。

关键词: 克隆代码, 克隆映射, 软件维护, 演化分析, 克隆质量