a sophisticated write-caching system with the purpose of extending the life of live USB flash drives. Puppy Linux includes the ability to use a normal persistent updating environment on a write-once multisession CD/DVD that does not require a rewritable disc; this is a unique feature that sets it apart from other Linux distributions. While other distributions offer live CD versions of their operating systems, none offer a similar feature. Puppy's bootloader does not mount hard drives or connect to the network automatically. This ensures that a bug or even unknowingly incompatible software won't corrupt the contents of such devices. Puppy Linux offers a session save on shutdown. Since Puppy Linux fundamentally runs in RAM, any files and configurations made or changed in a session would disappear otherwise. This feature enables the user to either save the contents to a writable storage medium, or write the file system to the same CD containing Puppy, if "multisession" was used to create the booted CD and if the disc drive supports burning. This applies to CD-Rs as well as CD-RWs and DVDs. It is also possible to save all files to an external hard drive, USB stick, or even a floppy disk instead of the root file system. Puppy can also be installed to a hard disk. User interface The default window manager in most Puppy releases is JWM. Packages of the IceWM desktop, Fluxbox and Enlightenment are also available via Puppy's PetGet package (application) management system (see below). Some derivative distributions, called puplets, come with default window managers other than JWM. When the operating system boots, everything in the Puppy package uncompresses into a RAM area, the "ramdisk". The PC needs to have at least 128 MB of RAM (with no more than 8 MB shared video) for all of Puppy to load into the ramdisk. However, it is possible for it to run on a PC with only about 48 MB of RAM because part of the system can be kept on the hard drive, or less effectively, left on the CD. Puppy is fairly full-featured for a system that runs entirely in a ramdisk, when booted as Live system or from a 'frugal' installation. However, Puppy also supports the 'full' installation mode, which enables Puppy to run from a hard drive partition, without a ramdisk. Applications were chosen that met various constraints, size in particular. Because one of the aims