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Definition: storage vs. memory


Storage and memory are the two major holding areas in a computer, tablet or smartphone, and their interplay is the fundamental architecture of computer processing. In the past, storage and memory clearly referred to two separate objects, but today they do not because "memory" may refer to either one.

Storage Is "Non-Volatile"
Storage comprises hard drives and solid state drives (SSDs), which hold programs and data. The primary attribute of storage is that it retains its content when the power is turned off. USB drives and optical discs are also storage.

Memory (RAM) Is "Volatile"
Memory is made up of "random access memory" (RAM) chips, which are upgradable by the user in a desktop computer but not in a phone or tablet. In contrast to storage, memory (RAM) loses all of its content when the power is turned off. See RAM.

To cover all bases (and add some confusion), there actually are RAM chips that are non-volatile. They serve as both storage and RAM in remote sensors and similar devices but not as the memory in computers, phones and tablets (see non-volatile memory).

From Storage to RAM and Back Again
When an application is run, the software and data are copied from storage to RAM (read). The software instructions are executed in RAM to process the data. The updated data may be displayed or printed and then copied (written) back to storage. See 3 C's and byte addressable.

Why the Confusion?
The problem with these terms is that many storage devices today use "flash memory" chips (see below). Consequently, people think storage and memory are the same. To avoid confusion, refer to "storage" and "RAM" rather than storage and memory. For more details, see storage and memory.

  STORAGE DEVICES (Non-Volatile)

  hard drive        (magnetic disk)

  SSD               (flash memory)

  USB drive         (flash memory)

  SD Card           (flash memory)

  CompactFlash      (flash memory)

  CD-R              (optical disc)

  DVD-R             (optical disc)

  DVD-RAM           (optical disc)

  magnetic tape     (tape cartridge)


  MEMORY CHIPS (Volatile)

  dynamic RAM       (DRAM chips)

  static RAM        (SRAM chips)









The Correct Usage
These examples describe storage and memory correctly, from top to bottom: Chromebook Specs (see eMMC); Lenovo laptop; Apple iMac.






They're All Chips
RAM chips (top) and storage chips (bottom) may look alike, but RAM is faster and volatile, while storage is slower and non-volatile. The USB and CompactFlash cases were removed for this photo. See memory module, USB drive and CompactFlash.










Memory Is Not Storage
These are all storage products, but because "memory" implies permanence to non-technical people, the word is used for storage by countless vendors, big and small.






Storage-Memory Hierarchy
To learn how memory and disk caches work, see cache. SSDs are faster storage than hard disks (see SSD).






Not Always the Correct Terminology
Even in the Stone Age, people were confusing storage and memory. No wonder people are still mixing it up!