Storage Characteristics

Why storage characteristics differ

Sometimes we want storage that's super fast, but we don't really care if it sticks around past the point in time we turn off our computer. Other times we want storage that's going to store a ton of information, a lot of information, but we don't really care if we have fast access to it. And then sometimes we want something in between, where we want something that can be stored for a long period of time but we still want fast access to it. These are different characteristics of the different media that we have, and different purposes that we have.

There are a lot of different ways we could describe the media that we use, different characteristics that this media has. I'm only going to cover a few ones that we really do need to know, so let's go over volatile, nonvolatile and read-only memory.

Volatile and nonvolatile

The first characteristic is whether we want to store things just temporarily, like in the case of RAM. We really don't want to store this long term, so when we turn off our computer we want our RAM to actually do away with all of the data. We get a fresh start the next time, and there's no security concerns because the data goes away from the RAM. So we really just want something that's temporary.

Then we have something we want maybe to store long term, so we've got data that we store on something like a solid state drive. This is data that's going to remain even when we turn off the power, and so there's a long-term memory.

The difference with this is that we call this volatile memory — the memory that just sticks around for a short period of time and is for short term, such as RAM — and then there's the nonvolatile, the memory that sticks around a lot longer.

Read-only memory

Another characteristic that we commonly see when it comes to storage is ROM, read-only memory. An example of this might be this CD-ROM. The CD-ROM is a read-only memory, so we only read from this device, we don't really write. Now, there are some CDs that we can write to, but this particular one would be just a ROM, a read-only memory. That means that we can't write over this data, that the data is already on here and that it's not going to change at this point.

Another example of read-only memory is some of the chips on our motherboard. In fact, there is a specific component on our motherboard that we call the ROM, read-only memory. It's a component on the motherboard, and I believe on this motherboard it's right here, it's this component. It stores the BIOS, the basic input output system, which is the initial set of instructions that tell this computer how to start up and start functioning. So the BIOS is stored on that read-only memory.

Characteristics by type of media

Now, different characteristics are typically associated with different types of media. For instance, when it comes to nonvolatile memory — that means memory that we can store long term — an example would be if we store this on a punch card, that's long term; if we store it on magnetic media, that's long term; if we store it on CD-ROM, that's long term. That's all nonvolatile, that means we don't have to continue to apply power to it to keep it stored. So paper, optical and magnetic would all be considered nonvolatile.

When we talk about read-only memory, typically our CDs are CD-ROMs, read-only memory, so that would be an example of a read-only memory. And the same thing with our punch cards would be read-only, right? And so we have the read-only memory here that's associated with those two, versus magnetic media is not read-only — usually we can write to it and then also write over that and write out many different times to that magnetic media.

Solid state is interesting. Solid state can actually be volatile or nonvolatile, and it could also be read-only memory.