Glossary · Hardware

RAM (Random Access Memory)

RAM is fast, temporary memory where a computer keeps the data and programs it is actively using; its contents are lost without power.

Updated October 6, 2026

RAM (Random Access Memory) is the short-term working memory of a computer. It holds the operating system, running programs and open data so the CPU can reach them far faster than from storage, and it is erased when power is lost.

Why it matters

When RAM fills up, the operating system starts moving data to a swap file on disk, which is much slower and makes a system sluggish. On servers, running out of memory can cause processes to be killed and sites to go down.

Common types are DDR4 and DDR5 for desktops and servers, with LPDDR in phones and thin laptops.

Example

$ free -h
              total   used   free  available
Mem:           15Gi   6.2Gi  1.1Gi      8.4Gi
Swap:         2.0Gi     0B   2.0Gi

This machine has 15 GiB of RAM, roughly 8.4 GiB of which is available to new programs, and no swap in use.

Common misconceptions

  • RAM and storage are the same. Storage keeps data permanently, RAM only while powered.
  • Free RAM is always good. Unused memory is wasted, and systems use spare RAM as file cache.
  • More RAM makes a computer faster in general. It only helps if you were running short.

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