When correcting a fault, adding a new concept or feature, or adapting a system to conform to a new platform, software engineers must first find the relevant parts of the code that correspond to a particular change. This is termed as concept or feature location process. Several techniques have been introduced which automate some or all of the process of concept location. Those techniques rely heavily on code comprehension as it is considered a prerequisite when attempting to maintain any software system. It provides a comprehensive overview of large body work which is beneficial to researchers and practitioners. This paper presents an overview of code comprehension categorization and consequence. A systematic literature survey of concept location enhancement techniques is also presented. Moreover, the paper presents an overview of the role of concept location in program comprehension and maintenance and discusses information retrieval techniques to advance concept location.