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A live CD, live DVD, or live disc is a complete bootable computer installation including operating system which runs in a computer's memory, rather than loading from a hard disk drive; the CD itself is read-only. It allows users to run an operating system for any purpose without installing it or making any changes to the computer's configuration. Live CDs can run on a computer without secondary storage, such as a hard disk drive, or with a corrupted hard disk drive or file system, allowing data recovery. A live ISO is an ISO image of a Live CD which can be used in virtual machine environments, mounted as if it were a CD/DVD and used as the virtual machine's boot CD. Live CDs, ISOs, and images usually include an operating system available without charge or restrictive license such as Linux, rather than a commercial one such as Microsoft Windows, for legal rather than technical reasons. The functionality of a live CD is also available with a bootable live USB flash drive, or even an external USB drive. These may have the added functionality of writing changes on the bootable medium. Write-locked Live SD WORM systems are the direct solid-state counterpart to live CDs, and can be booted natively in a media card slot or by using a USB adapter. Write-locked Live SD systems avoid excessive write cycles or corruption by ill-conditioned software, such as malware. While a live CD typically does not alter any operating system or files already installed on a computer's secondary storage (such as hard disk drives), many live CDs include software mechanisms and utilities for altering the host computer's data stores, including installation of an operating system. This is important for the system management aspect of live CDs, which can be useful for removing malware, for disk imaging, and for system recovery. Unless such software is used, at the end of a live CD session the computer remains as it was before. The live system is able to run without permanent installation by placing the files that normally would be stored on a hard drive into RAM, typically in a RAM disk. The computer must have sufficient RAM both to store these files and maintain normal operation. == History == All except the earliest digital computers are built with some form of minimal built-in loader, which loads a program or succession of programs from a storage medium, which then operate the computer. Initially a read-only medium such as punched tape or punched cards was used for initial program load. With the introduction of inexpensive read-write storage, read-write floppy disks and hard disks were used as boot media. After the introduction of the audio compact disc, it was adapted for use as a medium for storing and distributing large amounts of computer data. This data may also include application and operating-system software, sometimes packaged and archived in compressed formats. Later, it was seen to be convenient and useful to boot the computer directly from compact disc, often with a minimal working system to install a full system onto a hard drive. While there are read-write optical discs, either mass-produced read-only discs or write-once discs were used for this purpose. The first Compact Disc drives on personal computers were generally much too slow to run complex operating systems; computers were not designed to boot from an optical disc. When operating systems came to be distributed on compact discs, either a boot floppy or the CD itself would boot specifically, and only, to install onto a hard drive. The first live CD was FM Towns OS first released in 1989. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Live CD」の詳細全文を読む スポンサード リンク
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