Most office environments require people to perform a variety of general tasks, such as word processing, database queries, or spreadsheet analyses, and using productivity applications. These people may also be using applications that are specific to their particular business. Their companies have an installed base of PCs, peripheral devices and applications, and operating system allows them to maximize their investment in that computing infrastructure. Many companies have employees who spend a high percentage of their working hours away from the office - for example, at customer sites, in hotels, or out in the field - and rely on personal computers to help them perform their jobs. An operating system meets the requirements of these mobile computer users for the same application and device compatibility as their office-based colleagues, but also places lower demand on their hardware, including amount of memory, battery power, and use of disk space.