What is Computer Memory? RAM vs Hard Drive

Perhaps the most misunderstand concept amongst novice computer users/owners is the difference between RAM and Hard Drive space.

Knowing the difference becomes very important when trying to figure out why the latest and greatest "must have" software won't work on your computer. It also helps you figure out what needs to be done so it will work.

Hopefully this will answer the oft-asked question:

"It says I need 32MB RAM, but I have 800MB storage - that should be enough, right?"

Hard Drive

The Hard Drive may also be called "Storage" or "Disk Space" and it is measured in Megabytes (MB) or Gigabytes (GB).

A Hard Drive consists of a metal platter which spins very fast. As it spins, the hard drive "head" moves along the platter and can "read" and "write" information.

The hard drive is used for long term and large amounts of storage.

In your everyday life, when you "save" a file, you are asking the computer to "write" this information to the hard drive. There is normally a slight delay as the computer finds the right space on the hard drive and actually saves the information.

Once "saved", the information is magnetically encoded. As a result, it stays on the hard drive - regardless of whether you turn the computer off. The information stays there. And, later, you can erase your file and free up that space.

Advantages:
Relatively Cheap
Can turn off the computer, and reload the information later.

Disadvantages:
Since it's a mechanical device (spinning platter), it can be slow.

RAM

RAM may also be called "Memory" and it is measured in Megabytes (or MB).

RAM comes in the form of computer chips. These chips plug into special connectors in your computer. The purpose of these chips is to provide fast storage for the computer to use.

When the computer loads your file from your hard drive - where does that information go? It makes a copy of the information from the hard drive and places it in RAM.

Why? For speed. Information in RAM is stored based on electrical signals... so to change information simply requires sending a different electrical signal to the chip. This happens very quickly. Remember, the hard drive is a physical object that is spinning. It takes time to start it spinning, and move the hard drive "head" to the right position.

Let's say you are typing in a Term Paper in your Word Processor. Every key you press on the keyboard becomes part of your Term Paper. You don't realize it but, every letter you press has to be remembered by the computer. It accomplishes this by saving those keys in RAM. It happens so quickly, you don't even notice it.

So it's fast... but what happens when you turn off your computer? All the information is lost since the electrical signals storing the information have been turned off.

Advantages:
Fast

Disavantages:
"Forgets" when you turn the computer off
More expensive than hard drive storage.

Summary

So, as you can see, they are both necessary forms of storage and serve different purposes. Generally, a computer has far more Hard Drive storage than RAM. A typical computer one might purchase today might have 64 MB of RAM, and 2000 MB (or 2 GB) of Hard Drive storage.

For computer programs you purchase at the store: the minimum RAM requirements are usually less than the Hard Drive requirements. This is because programs will only load a small portion of information from the hard drive at a time. A good example of this is a game with many Levels. When you are playing on Level 1, there is no need to load any information (pictures, text) about Level 2 yet. However, all the information for Levels 1 through 30 need to be on the hard drive.


"It says I need 32MB RAM, but I have 800MB storage - that should be enough, right?"

So, it should be obvious now, that this person is comparing Apple and Oranges. He/She needs to see how much RAM their computer has to decide if they have enough.