How Computers Work · Inside a Computer · Lesson 2 of 5

CPU, Memory and Storage

The worker, the desk and the filing cabinet: how the big three work together.

The worker, the desk and the cabinet

Three parts do most of the everyday work: the CPU, the RAM and the storage. A simple picture makes them easy to remember.

Imagine a small office.

• The CPU is the worker. It reads instructions and does the jobs, one step after another, very fast.
• The RAM is the desk. Whatever the worker is using right now sits on the desk, close at hand.
• Storage is the filing cabinet. It holds every file and app you own, even the ones you haven't touched in years.

Here is what happens when you open a photo. The worker walks to the cabinet and finds the photo. It copies the photo onto the desk. Now the worker can look at it and change it quickly.

Why not work straight from the cabinet? Because the desk is much faster to reach. RAM is many times quicker than even a fast SSD.

What if the desk is too small? The worker has to keep putting things back in the cabinet and pulling them out again. That is slow. This is why a computer with little RAM feels sluggish when many apps or browser tabs are open.

A bigger cabinet does not make the worker faster. It just holds more files. So more storage means more room, and more RAM means more things open at once without slowing down.

Phones work the same way. When a phone says it has 8 GB of RAM and 256 GB of storage, that is the desk and the cabinet.

Cores, speed and why RAM forgets

When you shop for a computer, you will see words about the CPU like "8 cores" and "4.2 GHz". Here is what they mean.

A core is one worker inside the CPU chip. Old CPUs had one core. Most CPUs today have several, often 4 to 16. More cores means more workers, so the computer can do several jobs at the same time. One core can play your music while another loads a web page.

GHz, or gigahertz, is a measure of speed. It counts how many billions of steps a core can take each second. A 3 GHz core takes about three billion steps every second.

Higher numbers usually mean faster, but only when you compare CPUs of the same age and brand. A new 3 GHz chip can beat an old 4 GHz chip, because newer chips get more done in each step. So the model and year matter as much as the numbers.

Now, why does RAM empty when the computer turns off? RAM stores information as tiny electrical charges. Those charges need power all the time to stay in place. Cut the power, and they fade away in moments.

Storage is different. An SSD traps its data in a way that lasts with no power at all. A hard drive records it as tiny magnetic patterns on a disk.

That is why you save your work. Saving copies it from the desk into the filing cabinet. If the power goes out before you save, the copy on the desk is gone.