A portable application, is a computer software program that does not need to be installed or copied onto a computer's mass storage device to be executed, running instead from a removable storage device such as a CD-ROM drive, USB flash drive, flash card, or floppy disk. Portable applications can be run on any computer system with which they are compatible; they usually require a certain type of operating system (e.g., Microsoft Windows XP or above, any Linux, etc).