LARGE Software System Maintenance

This paper describes a methodology in maintaining large software system (system usually with more than 200,000 lines of code). The software system is not assumed to be well documented, nor does it have proper specification, making the process of understanding, updating and maintenance of the code extremely difficult and error prone. Our methodology proposes the use of knowledge base and theorem prover to understand the control flow and symbol usage of the software system and to show consistency between new updates and existing code.