Secondary Memory


  • Secondary memory is a non-volatile form of memory that is connected to the motherboard, but is not part of it.
  • Secondary memory is slower than primary memory because it is located further away from the CPU.
  • There are many forms of secondary memory that can be used for long term storage, backup or transfer of data including:
    • Hard Drives (direct access) Hard Drives are the most common form of secondary memory and are used to locally store and copy data.
    • Tapes (sequential access) Tapes are used in the industry to backup very large amounts of data
    • CD (direct access) CDs are used to Transfer music, data and are used sometimes for the backup of files.
    • USB Sticks (direct access) USB Sticks are used often as a portable form for data storage and are used to transfer data from one place to another.
    • Flash Memory (direct access) Flash Memory which includes SSDs, SD Cards, USB Sticks, which are used to transfer data form one computer to another, or store files on Cameras or MP3 Players.
    • DVD (direct access) DVDs are usually used to store Movies, Games and for backup.
    • ROM - ROM is a form of storage within the motherboard that stored the startup scripts for booting a computer.


Access time is different from the different storage devices to but also there are differences in speed inbetween each category in general.

There are two main forms of storing data in secondary memory
  • Sequential Access
    • On for example, Tapes information is stored in a line (one bit of information after another). To find the information you need to read one bit after another to locate the information.
  • Direct Access
    • Means that data can be located anywhere on the disk without having to shuffle through all the other data. This is accomplished differently depending on the form of storage.

Images

harddisksmall.jpg
A Hard Drive

CD_autolev_crop.jpg
A CD

Compact_audio_cassette_4.jpg
A Compact Casette

USB_Stick_128MB_Innenansicht.jpg
Internal view of a USB stick



Created By Daniel Gillo, edited by Jocbe
Last updated: 7. October 2010