Computer memory

In computing, memory is a device or system that is used to store information for immediate use in a computer or related computer hardware and digital electronic devices.[1] The term memory is often synonymous with the term primary storage or main memory. An archaic synonym for memory is store.[2]

Modern DDR4 SDRAM module, usually found in desktop computers.

Computer memory operates at a high speed compared to storage that is slower but offers higher capacities. If needed, contents of the computer memory can be transferred to storage; a common way of doing this is through a memory management technique called virtual memory.

Modern memory is implemented as semiconductor memory,[3][4] where data is stored within memory cells built from MOS transistors and other components on an integrated circuit.[5] There are two main kinds of semiconductor memory, volatile and non-volatile. Examples of non-volatile memory are flash memory and ROM, PROM, EPROM and EEPROM memory. Examples of volatile memory are dynamic random-access memory (DRAM) used for primary storage, and static random-access memory (SRAM) used for CPU cache.

Most semiconductor memory is organized into memory cells each storing one bit (0 or 1). Flash memory organization includes both one bit per memory cell and multi-level cell capable of storing multiple bits per cell. The memory cells are grouped into words of fixed word length, for example, 1, 2, 4, 8, 16, 32, 64 or 128 bits. Each word can be accessed by a binary address of N bits, making it possible to store 2N words in the memory.