1. A method comprising: operating on, and interfacing with an operating system of, a computer; providing runtime services, including a virtual file system, to a first program running on the computer and a second program running on the computer, the providing runtime services comprising: receiving, from the first program, first information and second information through a single file access routine of an application program interface (API) for the virtual file system; determining a selected one of multiple file storage areas to access based on the first information, the multiple file storage areas including a first area and a second area, the first area being local to the computer, accessible by the first program through the virtual file system and inaccessible by the second program through the virtual file system, and the second area being accessible by the first program and the second program through the virtual file system; mapping the second information to one or more file resources in the selected file storage area in the virtual file system; and accessing the one or more file resources for the first program.