What is the Difference Between Memory (RAM), Hard Drive, and Flash Memory?

Physically, RAM and hard drives are very different.

A hard drive is a mechanical box that contains a spinning metal disk similar to a CD and a moving read-write arm that slides across the spinning disk and either reads data from or writes data to the disk. Whenever a user installs an application on their computer the application is written to the hard drive permanently so that application can be used whenever it is needed. Likewise, when a user saves a document or a project on their computer, this data is also written to the hard drive.

RAM takes the form of removable computer chips that don't have any moving parts and temporarily store data on small circuit boards. RAM is temporary data storage because unlike hard drives, the data is only stored while the computer is up and running.

As a computer is being used data is constantly read from the hard drive and transferred into RAM so that it is more accessible to other parts of the computer such as the logic board and processor. However, as soon as the computer is shut down and turned off, all of the data inside of RAM dissipates and is gone. Data can be accessed from RAM at a much faster rate than data accessed from a hard drive because RAM doesn't require the use of a spinning disk and a moving read-write arm to scan for and retrieve data. So, in order to help computers operate more efficiently, data is loaded into RAM so that this data can be used at a moment's notice.

When a user launches an application like a word processor, the computer accesses the hard drive and reads all of the data required to open the word processor program and loads this data into RAM. The user may then create a new document and begin typing. Every letter and every character that is typed and displayed on a monitor is being stored in RAM. Of course most computer users know what happens when they get halfway through typing a letter or an important report and a power failure occurs before they've had a chance to save the document -- the document is gone forever.

However, if the document had been saved before the power failure occurred, then this document would have been written to the hard drive. Then when power is restored, the user can simply reboot his computer, launch his word processor, open his saved document from the hard drive and continue typing.