Why do computer need secondary storage?

Dae Yeon Koh
2 min readAug 19, 2021
Photo by Marc PEZIN on Unsplash

Short answer: secondary storage is needed when the RAM is full, and extra data needs to be off-loaded.

The longer answer is the rest of this article.

Basically there is a primary memory in a computer system. I talk about this and another type of memory storage in an article I made. Please click here if you don’t understand the terminology I will be talking about.

Anyway, there is a primary memory storage (mainly the RAM). This is where all of your data will reside, and be stored in. However, there is a problem. Since the primary memory (RAM) is volatile, once you turn off the computer, all the data you have created/used is lost. Vanished, like poof! You could say, “Wait hang on, there is ROM in primary memory, and that’s non-volatile. Can’t it be stored in that?”. Well, yes but actually no.

As we know from the previous article, RAM’s storage capacity is much larger than ROM, and the data you use from opening a document to simply typing anything is simply too much for the ROM to handle. And also, ROM can only read operations, while RAM can both read-and-write.

There is an excellent example about this scenario in the Core Computer Science for iB. I highly recommend to read it as it explains alot about primary and secondary storage and shows how they work together. Here it is:

Another disadvantage without secondary memory is that you have to reinstall all your application, software and data when you restart your computer.

And that concludes why computers need secondary memory. It’s a bit of a niche topic, but it’s an essential concept you need to understand if you want to study computing further.