Portable applications are modified versions of a desktop application that can be run on a USB drive. iPods, USB flash drives, external hard drives or any other portable device can be used. When the applications are stored on said device, the application can be used on any computer running the proper operating system by being plugged into the USB port on a computer. Most of the portable applications are still operating system dependent, but many have cross platform versions. Many open source and a few OEM applications have a portable counterparts. Numerous utility programs are available in a portable version as well.