The Basics of Memory
What is RAM and why do I care?
Technically speaking, RAM (random access memory) is any medium of storing information electronically so it can be accessed in a random sequence. This means some things we don't normally call RAM are also RAM. Hard drives, floppy discs, CD/DVD drives are all examples of data storage we don't generally refer to as RAM. However, they have identical characteristics.
The term RAM for electronic memory came at a time when mechanical mediums of data storage had such constraints as to require information to be recovered in a specific sequence. RAM was a revolutionary development in computing. It could be compared to the difference between a VCR and DVD player. The video cassette tape is strictly sequential in the order it could recover data. In this case, recover data means watch your recorded show. You had to queue it up to the spot (past the commercials) where you wanted to start viewing. Part of the beauty of DVD is that it can access information from the disc in just about any order, just like RAM. When the current generation of kids grows up, you'd have to explain to them the limitations of the VCR before the true beauty of the DVD's ability to access information at any sequence becomes apparent.
The term RAM or just memory in modern digital electronics is now synonymous with "electronic memory." Basically, it is binary data stored in a network of transistors rather than on a tape or a disc. This makes access to information incredibly fast compared to the optics in laser storage (CD/DVD) or the head in oxide storage medium (Hard drives, floppy discs). The key advantage of electronics storage is speed.
Just how fast is electronic memory?
The difference in speed between hard discs, CD/DVD and memory is so vast that the unit of measuring speed is different for the two different forms of storage. They're literally not even in the same league. The measure of speed is called "access time," which refers to the amount of time it takes to retrieve stored information. For disc drives this is measured in milliseconds or thousandth of a second. For electronic memory access times are measured in nanoseconds, which are a billionth of a second. You can see we completely skip over microseconds (one millionth of second) when going from disc storage to electronics storage.
The cost of all this speed is energy. Most RAM requires a constant source of electricity to actually store any information at all. Hard drives don't require power to save its information. This is why in most computer systems a hard drive feeds data to the memory. The CPU can then work directly with RAM at incredibly high speeds.
Mobile electronics such as cell phones and PDA devices work the same way even when they don't actually have a hard drive. Instead of a hard drive they use something called flash memory. Flash memory will provide data to the CPU, RAM and registers in much the same way as a computer. It's interesting to note that some handheld devices, such as cell phones and especially MP3 players, have built in micro hard drives. Generally, buying a unit of SD memory will cost a significant price for 2 gigabytes, but a built-in hard drive can get up to several gigabytes and keep the cost down considerably.
Let's examine the differences between disc and electronic storage in the next section of Memory Basics where we'll delve into the differences between System RAM and Flash.