With few exceptions, OSs require hard disk space. (The exceptions involve placing the OS on a removable medium, such as a floppy disk, or embedding it in the ROM of a specialized device such as a personal digital assistant [PDA].) Even if your multi-OS configuration uses a single partition, as in an installation of Windows 9x and a Linux variant that uses UMSDOS, each OS's files consume space on that partition. It is important before you embark on an OS installation to ensure that you have adequate disk space already or to obtain a new hard drive on which to install a new OS. Fortunately, you can often reduce total disk space requirements by sharing disk space for temporary files and the like.