Computer storage

Storage or Memory refers to those parts of a computer that retain information for some period of time. Primary Storage is typically high-speed memory where the computer keeps information that is actively being used (for example, the programs currently being run and the data they are operating on). Secondary Storage is where the computer stores information that is not necessarily in current use.

There are many terms for different types of computer storage devices: Volatile memory is memory that loses its contents when it loses power; Non-volatile memory does not. Removable storage consists of devices in which the physical storage medium itself can be carried from one computer to another (for example, floppy disks and compact discs. RAM (for random access memory) is memory that can be accessed in any order, as opposed to serial access memory that must be read sequentially (such as a reel of magnetic tape). There are many types of RAM, such as NVRAM (non-volatile RAM), and SRAM, DRAM, SDRAM, etc., which are all types of volatile RAM that differ in obscure ways not related to their basic function. ROM (for read-only memory) cannot be changed once initially programmed by the manufacturer. EPROM? (erasible programmable read-only memory) memory cannot be overitten in normal use, but can be erased and reprogrammed with special hardware. EEPROM? (for electrically erasible programmable read-only memory) is a type of EPROM that can be erased with less specialized hardware that is typically included on the computer that hosts it. WORM? devices (for write once/read many--a term typically used only for removable storage devices) can be initially programmed by the end user but not subsequently overwritten.

Each type of storage is suited for different purposes, and all computers contain several types.

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It seems this entry should be titled PC-Memory. What about tape drives, stationary disks, mountable disks, and to go back, core. And, PC can have tape drives, too. Or, going forward, organic memory.

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The description above is general and inclusive, as a top-level article should be, and concentrates more on types of memory organized by usage-related properties rather than device specifics. Perhaps a more organized set of links to specific devices would not be a bad idea to add as well. Something like:

• Primary Storage Devices
  • Magnetic Core
  • [Static RAM]?
  • [Dynamic RAM]?
  • Special-purpose primary storage
    • VRAM?
    • NVRAM?
    • WRAM?

• Secondary Storage Devices
  • Internal
    • Hard disk
    • ROM

• Removable
  • Magnetic
    • Magnetic tape
    • Floppy disks
  • Optical
    • CD-ROM
    • CD-R
    • CD-RW
    • DVD-ROM?
    • DVD-RAM?
    • [Mylar tape]?
    • [Paper tape]?
    • Punch card
  • Magneto-optical
  • Semiconductor-based
    • [Compact flash]?
    • Smartdisk?
    • [Memory stick]?

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What I still don't see are the external stationary and removable disks, used with mainframes.