In computer storage, secondary storage, or external memory, is computer memory that is not directly accessible to the central processing unit of a computer, requiring the use of computer's input/output channels. Secondary storage is used to store data that is not in active use. Secondary storage is usually slower than primary storage, or internal memory, but also almost always has higher storage capacity and is non-volatile, which makes it perfect for the preservation of stored information in an event of power loss. This article or section does not cite any references or sources. ... The terms storage (U.K.) or memory (U.S.) refer to the parts of a digital computer that retain physical state (data) for some interval of time, possibly even after electrical power to the computer is turned off. ... Die of an Intel 80486DX2 microprocessor (actual size: 12×6. ... The NASA Columbia Supercomputer. ... Energy Input: The energy placed into a reaction. ... In Computer Science, data is often distinguished from code, though both are represented in modern computers as binary strings. ... Primary storage, or internal memory, is computer memory that is accessible to the central processing unit of a computer without the use of computers input/output channels. ... It has been suggested that this article or section be merged with NVRAM. (Discuss) Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, is computer memory that can retain the stored information even when not powered. ...

Storage devices in this category include:

• CD, CD-R, CD-RW
• DVD
• Flash memory
• Floppy disk
• Zip Drive
• Hard disk drive
• Magnetic tape
• Paper tape
• Punch card
• RAM disk
• External Hard Drive
• Blu-Ray
• HD-DVD
• Thumb Drive

Almost all storage devices are either magnetic or optic. A well known exception is provided by flash memories (used in digital audio players, usb stick memories, etc.) which uses a different approach. A Compact Disc or CD is an optical disc used to store digital data, originally developed for storing digital audio. ... This article does not cite any references or sources. ... Compact Disc ReWritable (CD-RW) is a rewritable optical disc format. ... DVD (Digital Versatile Disc or Digital Video Disc) is an optical disc storage media format that can be used for data storage, including movies with high video and sound quality. ... A USB flash drive. ... A floppy disk is a data storage device that is composed of a disk of thin, flexible (floppy) magnetic storage medium encased in a square or rectangular plastic shell. ... Iomega ZIP-100 Drive Logo An internal Zip drive. ... The inside of a hard disk drive displaying the actuator arm traveling over the top platter. ... Magnetic tape has been used for data storage for over 50 years. ... A roll of punched tape Punched tape is an old-fashioned form of data storage, consisting of a long strip of paper in which holes are punched to store data. ... Punched cards (or Hollerith cards, or IBM cards), are pieces of stiff paper that contain digital information represented by the presence or absence of holes in predefined positions. ... A RAM-Disk, Ramdisk or Ramdrive is a virtual solid state disk that uses a segment of active computer memory, RAM, as secondary storage, a role typically filled by hard drives. ... It has been suggested that Disk enclosure, USB enclosure be merged into this article or section. ... Blu-ray discs Blu-ray Disc is a next-generation optical disc format jointly developed by a group of leading consumer electronics and PC companies called the Blu_ray Disc Association (BDA), which succeeds the Blu_ray Disc Founders (BDF). ... HD DVD, or High-Definition DVD is a high-density optical disc format designed for the storage of data and high-definition video. ... A USB keydrive, shown with a US quarter coin for scale. ... In physics, magnetism is a phenomenon by which materials exert an attractive or repulsive force on other materials. ... See also list of optical topics. ... A USB flash drive. ... A hard-drive-based player (Apple iPod) An MP3 CD player (Philips Expanium) A flash-based player (iBox Mediaman) A digital audio player (DAP) is a device that stores, organizes and plays digital music files. ... A USB flash drive, shown with a 24 mm U.S. quarter coin for scale. ...

The secondary storage is often formatted according to a filesystem format, such as ext3 or ntfs which provides the abstraction necessary to organize data into files and directories, providing also additional information (called metadata) describing the owner of a certain file, the access time, the access permissions, and other information. See Filing system for this term as it is used in libraries and offices In computing, a file system is a method for storing and organizing computer files and the data they contain to make it easy to find and access them. ... The ext3 or third extended filesystem is a journalled file system that is commonly used by the Linux operating system. ... NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, and Windows Vista. ... A file in a computer system is a stream (sequence) of bits stored as a single unit, typically in a file system on disk or magnetic tape. ... This article is about the computing term. ... The simplest definition of metadata is that it is data about data. ...