中文摘要：

本文应用双边市场框架，选取市场中应用软件的均衡种类为落脚点，指出相比社会最优，商业专用操作系统厂商吸引了过少的应用开发商；而开放源操作系统同样无法达到社会最优，相比商业专用情形，不一定总能改善市场中提供的应用软件种类，而是取决于应用软件市场特征；同时，研究还揭示了，操作系统应用程序接口的设计是平台厂商降低应用软件开发成本、协调双边市场需求的有效手段；最后，探索性地阐明了一体化关键性应用软件生产是平台厂商营建商业生态系统的有效途径。

英文摘要：

By analyzing the equilibrium number of varieties of application software, this paper studies the market performance and social welfare of the software industry based on the two-sided markets theory. Compared with the first-best number of application software varieties, proprietary operating systems attract less applications. For open-source operating systems, the number of application varieties is larger or smaller than in the proprietary case depending on the characteristics of the market of application software. Besides, the design of APIs is found to be the way to help reduce the cost of application developers, thus enhancing the profitability of operating systems.