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Definition: storage vs. memory


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

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 main memory in computers, phones and tablets because they are more costly (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 storage; write RAM). The software instructions are executed in RAM to process the data. Updated data may be displayed or printed and then read from RAM and written to storage. See 3 C's and byte addressable.

Why the Confusion?
Many storage devices today use "flash memory chips," which is one reason for the mistake (see below); however the storage and memory terms have been misued long before USB drives and SSDs became popular. 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.




Disk Memory in 2022!
The term "disk memory" only adds confusion for anyone learning the field, yet this is common; witness the number of search results.


  STORAGE DEVICES (Non-Volatile)

  Device          Type
  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)

  Type            Chip Type
  dynamic RAM     DRAM chips
  static RAM      SRAM chips








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 mixing up the terms!