RAM (pronounced ramm) is an acronym for random access memory, a type of computer memory that can be accessed randomly; that is, any byte of memory can be accessed without touching the preceding bytes. RAM is found in servers, PCs, tablets, smartphones and other devices, such as printers.
Main Types of RAM
There are two main types of RAM:
DRAM (Dynamic Random Access Memory)
SRAM (Static Random Access Memory)
DRAM (Dynamic Random Access Memory) – The term dynamic indicates that the memory must be constantly refreshed or it will lose its contents. DRAM is typically used for the main memory in computing devices. If a PC or smartphone is advertised as having 4-GB RAM or 16-GB RAM, those numbers refer to the DRAM, or main memory, in the device.
More specifically, most of the DRAM used in modern systems is synchronous DRAM, or SDRAM. Manufacturers also sometimes use the acronym DDR (or DDR2, DDR3, DDR4, etc.) to describe the type of SDRAM used by a PC or server. DDR stands for double data rate, and it refers to how much data the memory can transfer in one clock cycle.
In general, the more RAM a device has, the faster it will perform.
SRAM (Static Random Access Memory) – While DRAM is typically used for main memory, today SRAM is more often used for system cache. SRAM is said to be static because it doesn’t need to be refreshed, unlike dynamic RAM, which needs to be refreshed thousands of times per second. As a result, SRAM is faster than DRAM. However, both types of RAM are volatile, meaning that they lose their contents when the power is turned off.
The Difference Between Memory, RAM and Storage
Sometimes, people get confused about the difference between memory and storage, in part because both can be measured in megabytes (MB), gigabytes (GB) and terabytes (TB).
In common usage, the term RAM is synonymous with main memory. This is where a computing system stores data that it is actively using. Storage systems, such as hard drives, network storage devices or cloud storage, are where a system saves data that it will need to access later.
Computing systems can retrieve data from RAM very quickly, but when a device powers down, all the data that was in memory goes away. Many people have had the experience of losing a document they were working on after an unexpected power outage or system crash. In these cases, the data was lost because it was stored in system memory, which is volatile.
By contrast, storage is slower, but it can retain data when the device is powered down. So, for example, if a document has been saved to a hard drive prior to a power outage or system crash, the user will still be able to retrieve it when the system is back up and running.
Storage is usually less expensive than RAM on a per-gigabyte basis. As a result, most PCs and smartphones have many times more gigabytes of storage than gigabytes of RAM.