Quality and security of software are key factors in the software development. This thesis deals with the quality of open source software (OSS for short) and different questions that are related with open source and close source software has discussed in the thesis proposal. Open source software is a process by which we can produce cheap and qualitative software and its source could be re-use in the development of the software. Close source software is more expensive than open source software and we can not re-use its source code, so there should be a way by which cheap and qualitative software should be produced. This thesis describes that how the quality of the open source software can be evaluated and increased. There are different factors which are helpful to increase the software quality these factors are low cycle time, low cost and small size of software. These factors are also helpful for the development of software product according to the requirement of clients and the users of that software. This thesis also describes the security and performance of close and open source software and it also analyze different software development processes. The quality of OSS can be increased by use of best evaluation techniques, best quality measurement, best development tools and best development process. There are also many challenges for OSS, which it has to face for improvement of the quality of OSS. Initially there were many drawbacks in open source software but with the passage of time improvement has produced in it. This thesis also describes the compression, advantages and disadvantages of the close source and open source software.3