Computer memory can refer to many types of memory within a computer, but, typically, it refers to random access memory (RAM). It is physically found on computer chips that are inserted onto the computer’s motherboard. RAM is electronic, rather than mechanical; that is, it does not have moving parts and therefore data access to it is very fast. Modern computers often have somewhere between 256 MB (megabytes) and 2 GB (gigabytes) of RAM, although there are, of course, computers with more or less RAM. RAM is also volatile, meaning that it gets lost when the computer is switched off.
The expensive nature of RAM spurred the creation of another type of computer memory called virtual memory. With virtual memory, a slow down in performance is observed only when you try to operate a program whose files are in the virtual memory. In essence, this slow down is only observed when shifting between programs. In this way, virtual memory often provides a cheaper alternative to RAM.
A third type of computer memory is cache. There are two types of cache. Primary cache, or level 1 cache, is built right into the central processing unit (CPU) and ensures instant availability of data that the CPU frequently needs. Secondary cache, or level 2 cache, is usually built on a memory chip, is located very close to the CPU, and has a direct connection to the CPU through a dedicated circuit. Secondary cache is bigger in capacity than primary cache. Cache basically speeds up the rate at which data moves from the main memory to the CPU.
The registers form a fourth type of computer memory. These are units within the CPU that contain specific types of data, especially for the Arithmetic and Logic Unit (ALU). A final group of computer memory is called flash. This is a solid-state, rewritable type of memory. Examples of flash memory include BIOS and memory cards. Just like the RAM, they are electronic and not mechanical. They are also non-volatile, and are therefore suitable for digital cameras, mobile phones and other miniaturized computers.