This contrasts with memory, whose contents can be accessed (i.e., read and written to) at extremely high speeds but which are retained only temporarily (i.e., while in use or as long as connected to a power supply). The function of memory is to serve as a high speed intermediary, providing enough data for the CPU (central processing unit) to use at any given time without making it wait for the much slower storage and thereby slow down the entire system. Memory is constructed from semiconductor chips (which are, in turn, incorporated into multi-chip modules) called random access memory (RAM).
As compared with memory, storage not only (1) has much slower access speeds, but also (2) has a much larger capacity (and a much lower cost), (3) retains programs and data regardless of whether it is currently in use or not and (4) is non-volatile (i.e., retains its contents regardless of whether or not it is connected to power supply).
Flash memory, a type of electrically erasable programmable read-only memory (EEPROM), has characteristics of both memory and storage. That is, access speeds and access techniques are similar to those of RAM, but data can be retained for long periods (at least ten years) without any need for a power supply. This unique combination has made flash memory increasingly popular, particularly for use in USB (universal serial bus) key drives (also called flash memory drives) and for image storage cards for digital cameras.
There is a close relationship between storage and memory. This is because data frequently moves back and forth between the two at high speed when a computer is in operation. The relationship is particularly intimate in the case of virtual memory, which is the use of space on a HDD to simulate additional RAM by transferring data that is not immediately needed to the HDD and then copying it back into memory when it is needed again.
Created January 6, 2005. Updated July 27, 2006.