Every computer has an operating system, which is a program that controls that computer's resources. Some of the functions of an operating system are to read and write data, allocate main memory, perform memory swapping, start and stop programs, respond to error conditions, and facilitate backup and recovery. In addition, the operating system creates and manages the user interface, including the display, keyboard, mouse, and other devices. Although the operating system makes the computer usable, it does little application-specific work. Application programs are software that are processed on the client or server computer. If you want to check the weather or access a database, you need application programs such as an iPad weather application or Oracle's customer relationship management (CRM) software.