From time to time, I'll be writing educational blog posts. In these posts I'll explain some basic aspects of computing that some of my readers/clients might not be familiar with, and may help them better understand the tools they're using.
In this post, I'll be discussing the topic of memory. I'll focus on the two most common types that someone might be referring to when mentioning "memory" as it pertains to computers. In your average desktop or laptop computer, you'll most likely have two kinds of memory: storage and system.
Storage Memory:
Storage is fairly easy to understand and is the most familiar kind to most computer users. Storage memory is where all the files/data is stored on your computer, files like your documents and music, but also files like all the information that Windows needs in order to run, or the applications you use.
Storage usually takes the form of hard drives, which are usually large both in physical size and in their data capacity. These days, typical hard drive sizes are about 1TB for desktop hard drives and 500GB for laptops, and desktop drives currently max out at 4TB. Lastly, hard drives are able to retain the data that is written to them even if they aren't receiving power.
System Memory:
System memory is a little more complicated. In a typical computer, your system memory comes in the form of RAM. When your computer starts up and Windows begins to load, it is put into your system memory. The reason for this is that system memory is far faster than storage memory, so your computer would rather work from information stored in RAM than from a hard drive. When you open up an application that's installed on your computer, what's really happening is that the files are being read from the hard drive and loaded into RAM, then the CPU works with that data from there because it's faster. While you have the program open, all the data needed to run that program is kept in RAM.
This explains why your computer slows down the more programs you have open. At a certain point, the data required to run each program adds up to more than the total system memory you have, and the computer has to pull more and more from the hard drive instead of the RAM, slowing everything down. The more RAM you have installed, the harder it is to fill up and the more programs you can have open. When your computer is shut down, the RAM is cleared out because it's incapable of storing information when it isn't receiving power. That's why you lose what you're working on in Word if your power goes out and you didn't save your document.
The Concept:
Here's a good way to visualize storage vs system memory, or hard drives vs RAM: imagine an office.
Think of an office that has nothing but an empty desk and a full file cabinet, and then think about starting a project. Your project requires information from the file cabinet, so you go over and pull out the stuff you'll need, then bring it over the the desk where you lay it out and start to work. Because you grabbed everything you need from the file cabinet, you're able to quickly grab stuff from your desk as you need it. But if you forgot something, you have to stand up, walk back to the file cabinet, and get it. Similarly, if you don't have enough room on your desk, you're not going to be able to grab as much from the file cabinet in the first place, and you'll only be able to work on a smaller number of things at once. If you bring in another piece of furniture to extend your desk space, or buy a new, larger desk, you'll be able to work on more things at once and you'll be more productive. If you buy another file cabinet or replace it with a bigger one, you'll be able to store more information.
As you can see, the file cabinet is your hard drive and the desk is your RAM. The practical difference between the two is that adding more hard drive space improves capacity, while adding more RAM improves performance.