When you have something “open” on your computer, whether it is a document, web browser, or a game, it has to be held somewhere. Everything on your computer is likely stored on hard drives (HDD), so why can’t the open programs just be held there? Well, the problem with HDD is they are slow, relative to other technologies, so if the HDD held the program, it would run too slow to be useful. That’s why we have RAM.
RAM is random-access, which means it can read or write data, wherever it may be, in the same about of time. HDDs, on the other hand, read data sequential, taking time to find the data you need. This makes RAM much better for programs that are currently open, needing to read and write quickly and frequently. When a program is opened, the data associated with the program is read from your HDD and written to RAM. It stays in RAM until you close the program. When you save your work, the data in RAM is written to your HDD. Then, when the program is closed, its data is cleared from RAM.
RAM is constructed in what are called dimms. Think of them as sticks of RAM. Most dimms are one of these sizes: 1, 2, 4, 8, or 16 Gbs, although other sizes do exist. RAM dimms connect into the computer’s motherboard. Motherboards vary in the number of dimm slots they have, from 1 to as many as 6.
RAM is also volatile. That means that when RAM loses power, it loses all the data it was storing. That’s why when you have a program open, and turn the computer off, when you turn it back on, its not open anymore. RAM is also much more expensive and has much less space than a HDD.
In addition to RAM, your computer also has something called “virtual memory”. Virtual memory is a way of extending the amount of RAM you have by telling your computer a part of your HDD is RAM. Now, this lets you have more RAM, using what’s called a paging file, by swapping data in RAM with data in the paging file when RAM is being used to capacity, but, because the HDD is considerably slower than RAM, this will have a noticeable impact on the response time of the program you are using.
Overall, RAM’s purpose is to store data that is being used currently in a faster space than your long term storage medium. Without it, working with data would be an incredibly slow process. Well, technically, without any RAM, your computer would detect no RAM, and refuse to turn on. So, it is also important in that regard.