AI Term of the Moment
AI persona
Definition: storage vs. memory
Storage and memory are the two holding areas for programs and data in every computing device, and their interplay is how computers work. Unfortunately, the term memory sometimes refers to storage, which only adds confusion.
Storage Is "Non-Volatile"
Storage comprises hard drives and solid state drives (SSDs). Storage retains its content when the power is turned off. USB drives and optical discs are also storage.
Memory (RAM) Is "Volatile"
Memory is "random access memory" (RAM), and dynamic RAM (DRAM) is the common technology. In contrast to storage, memory loses its content when the power is turned off. It is upgradable in a desktop computer and sometimes in a laptop but not in a mobile device. See RAM.
From Storage to Memory and Back Again
When an application is run, the software and data are copied from storage to memory (read storage; write memory). The software instructions are read from memory and executed, and the data in memory are processed by the CPU. Data in memory may be displayed or printed and then read from memory and written to storage if there were changes. See 3 C's and byte addressable.
Why the Confusion?
Solid state storage drives (SSDs) and USB drives are made of "flash memory chips," an unfortunate name because it helps confuse the distinction between storage and memory. Imagine if the brake and accelerator in a car were transposed all the time. Consequently, the non-technical consumer may never know that storage and memory are not the same. For more details, see storage and memory.
Correct Usage
They're All Chips
Incorrect Usage
Storage-Memory Hierarchy
Storage Is "Non-Volatile"
Storage comprises hard drives and solid state drives (SSDs). Storage retains its content when the power is turned off. USB drives and optical discs are also storage.
Memory (RAM) Is "Volatile"
Memory is "random access memory" (RAM), and dynamic RAM (DRAM) is the common technology. In contrast to storage, memory loses its content when the power is turned off. It is upgradable in a desktop computer and sometimes in a laptop but not in a mobile device. See RAM.
From Storage to Memory and Back Again
When an application is run, the software and data are copied from storage to memory (read storage; write memory). The software instructions are read from memory and executed, and the data in memory are processed by the CPU. Data in memory may be displayed or printed and then read from memory and written to storage if there were changes. See 3 C's and byte addressable.
Why the Confusion?
Solid state storage drives (SSDs) and USB drives are made of "flash memory chips," an unfortunate name because it helps confuse the distinction between storage and memory. Imagine if the brake and accelerator in a car were transposed all the time. Consequently, the non-technical consumer may never know that storage and memory are not the same. For more details, see storage and memory.
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
This example describes storage and memory correctly.
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.
These examples reference storage, not memory. The problem is that "memory" implies permanence to non-technical people, but the word is used for storage by vendors, big and small.
To learn how memory and disk caches work, see cache. SSDs provide faster storage retrieval than hard disks (see SSD and hard disk).