2020-09-24
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Random Access Memory (RAM) is the hardware in a computing device where the operating system (OS), application programs and data in current use are kept so they can be quickly reached by the device's processor. RAM is the main memory in a computer, and it is much faster to read from and write to than other kinds of storage, such as a hard disk drive (HDD), solid-state drive (SSD) or optical drive.
RAM is still faster than any other memory except for the small CPU cache. So RAM speeds up the computer a lot (compared to building a new computer without RAM).
And because for a long time all computers have had RAM a lot of systems rely on it.
There's a program in all computers, smartphones, routers,... that upon turning the device on copies some instructions into a specific address in memory and then the CPU reads from that address and starts working. So without RAM the device will not work.
Random-access memory (RAM) is a type of computer data storage. A RAM device makes it possible to access data in random order, which makes it very fast to find a specific piece of information. Certain other types of storage are not random-access. For example, a hard disk drive and a CD will read and write data in a predetermined order. The mechanical design of these devices prescribes that data access is consecutive. This means that the time it takes to find a specific piece of information can vary greatly depending on where it is located on the disk.
So, RAM is used by the central processing unit (CPU) when a computer is running to store information that it needs to be used very quickly, but it does not store any information permanently.
Present-day RAM devices use integrated circuits to store information. This is a relatively expensive form of storage and the cost per unit of storage is much higher than for devices like a hard drive. However, the time to access data is so much faster for RAM that speed outweighs cost. A computer, therefore, uses a certain amount of RAM for fast-access, temporary storage of information and a much larger amount of non-random, permanent mass storage, like a hard disk drive. For example, a typical computer system may have two to eight GB (gigabytes) of RAM, while the storage capacity of the hard disk drive can be several hundred GB or even one TB (terabyte).
Dynamic RAM is the most common type of memory in use today. Inside a dynamic RAM chip, each memory cell holds one bit of information and is made up of two parts: a transistor and a capacitor. These are, of course, extremely small transistors and capacitors so that millions of them can fit on a single memory chip. The capacitor holds the bit of information -- a 0 or a 1 (see How Bits and Bytes Work for information on bits). The transistor acts as a switch that lets the control circuitry on the memory chip read the capacitor or change its state.
Static RAM uses a completely different technology. In static RAM, a form of flip-flop holds each bit of memory (see How Boolean Gates Work for detail on flip-flops). A flip-flop for a memory cell takes 4 or 6 transistors along with some wiring, but never has to be refreshed. This makes static RAM significantly faster than dynamic RAM. However, because it has more parts, a static memory cell takes a lot more space on a chip than a dynamic memory cell. Therefore you get less memory per chip, and that makes static RAM a lot more expensive. However, SRAM is significantly faster and uses less power than DRAM. The price and speed differences mean static RAM is mainly used in small amounts as cache memoryinside a computer's processor.
So static RAM is fast and expensive, and dynamic RAM is less expensive and slower. Therefore static RAM is used to create the CPU's speed-sensitive cache, while dynamic RAM forms the larger system RAM space.
