Learn about Computer Memory

In a previous blog post we learned about how computers use something called "binary" to represent information as a bunch of 0s and 1s. But how do computers store all of this information? How does computer memory work?

For this activity to make the most sense, please complete these other activities first:

In the old days, early computers stored information using cards. Humans would punch holes into these cards in a specific pattern, where each column represented one byte of information (remember: one byte is made up of 8 bits, and can represent a single letter or number). To run a program you would sometimes need a whole stack of cards! You also couldn't reuse the cards for different programs, so you needed a lot of different stacks. As you might have guessed, this type of computer memory isn't used anymore.

Most modern computers use something called a "hard drive" to store information. A hard drive contains metal disks and electromagnets on movable arms.

To store a bit of information on a hard drive, the electromagnet moves to a specific location on the disk and makes the north pole of a very tiny magnet face one direction or the other (1 or 0). The electromagnet has to move very quickly and carefully!

For this activity, we will be building a model of a single bit of memory similar to what you would find in a hard drive. We will also be using the electromagnet from a previous activity to write information to this bit! What you will need:

  • Toilet paper roll
  • Two circular magnets that are the same size (check out out our themed magnets!)
  • Straw
  • Q-tip or toothpick
  • Electromagnet (from this activity)
  • Scissors
  • Marker

First, make the stand using the toilet paper roll. You will need to cut four notches in the top, and four notches in the bottom. Make sure the notches at the top are at least as long as your magnet.

 

Fold the bottom tabs out and fold two of the top tabs inside the toilet paper roll.

Next, carefully poke holes through the top tabs that are big enough for your Q-tip or toothpick to fit through. Put the stand aside for now.

Next, make the switch. Cut a piece of straw that is a little bit wider than your magnet, and tape it to the back of the magnet. It is very important that the straw is in the middle of the magnet so that your switch will be balanced.

Then tape two small pieces of straw to either side of the long straw.

Tape the second magnet on top of the straws, making sure that it lines up with the first magnet. Tape around the entire switch so that it holds together well.

 

Next, thread the switch onto the Q-tip or toothpick so that it rests on the stand. Tape the stand to the table so that it is secure.

 

Finally, test out your switch using your electromagnet! Try touching either end of the nail to the switch (if it is balanced well you might not even have to touch the magnet, just get close). This is similar to how an electromagnet inside a hard drive makes the tiny magnets face one direction or the other to represent either a 1 or a 0.

If you are having a hard time with getting your switch to work, here are a few tips for troubleshooting:

  • Check that the magnets are balanced - if not, adjust the straws
  • Check that the magnets aren't catching on the toilet paper roll - if they are, cut or fold the roll out of the way
  • Check that the straw isn't catching on the toilet paper roll - if it is, cut it shorter
  • Make sure the battery for your electromagnet is new or fully charged

Take a second to think about this - we have built one switch that represents a single bit of information. We know that there are 8 bits in a single byte. From our Metric Scale Scavenger Hunt we learned that if a byte were the size of a grain of rice, a computer with 1 TB of memory would be the size of the CN tower. It is absolutely amazing how much information can be stored on such a small hard drive! 

But hard drives aren't perfect. They are a bit slow since the electromagnet has to move around to get to the right part of the disk. They can also lose their memory if they are dropped or get too close to a magnet! Newer computers are starting to use a type of memory called a "Solid State Drive". These drives use electricity to store information instead of electromagnets, so they are faster and easy to carry around.

I hope you enjoyed learning more about computer memory! If you discover any tips for troubleshooting your switch please leave them in the comments below.

This activity is based on the book If: Ball, Then: Catch, available here!


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