to apps for particular operating systems and hardware, there are also cross-platform mobile apps. These can operate on multiple operating systems and hard- ware devices. Large, multinational mobile operators such as Telecom Italia Mobile and Telefónica offer cross-platform app stores for mobile apps that operate on the hundreds of different devices in the various countries in which they offer service. They do this by providing a software interface called an Application Programming Interface (API) that translates data between the mobile application and the particular operating systems and mobile devices. Applications and Services Apps as a Strategy to Retain Customers Mobile apps help carriers cement relationships with customers even as they provide revenue. The rationale is that customers will be reluctant to move to other carriers if it means that they lose their mobile apps. For example, Telefónica is in the process having social networking software developed that will enable its customers to access mobile apps from within social networking sites. It is hoped that the close association between the mobile apps and the carrier will enhance the customer's relationship with Telefónica. Worldwide Mobile Apps Compatibility Currently, computer owners can move their documents and most of their applica- tions when they upgrade their computers. Applications that are not compatible with a new computer can generally be upgraded with minimal effort. Downloading music and PDF files from the Internet works seamlessly on most computers. This is not the case with tablets and smartphones for which apps are not portable and most often are designed to work only on particular operating systems. Therefore, such files can't be moved to new phones that use different operating systems. They are not necessarily portable between operators either. The Wholesale Applications Community (WAC) organization hopes to change this by establishing a uniform core set of standards for interfaces between applications and operating systems. It hopes t