Computer Memory: How Does RAM Work?

By Michael Quarles

How does RAM work? Is it some form of technical wizardry, beyond the understanding of average folks?

My answer would be “no”. Actually, in concept it’s quite simple. RAM is filled with microscopic capacitors. Each of these capacitors can do one of two things: they can hold a charge, or not hold a charge. This is the most basic level of information inside your computer.

Yet this function can be made to store anything from your child’s book report to a 3-D drawing program. How is this possible?

Those tiny capacitors, that can only hold a charge, or not hold a charge, are arranged in banks of eight. If a capacitor has a charge, it is given a value of “1”. If it doesn’t hold a charge, it carries a value of “0”.

Imagine these banks of capacitors using their charges to hold what seem to be rather peculiar numbers. Say the first capacitor has no charge, making it a “0”. The second has a charge, making it a “1”. Our third, fourth, fifth, sixth, and seventh capacitors have no charge, making them “0”. Finally, the eighth has a charge, and therefore is “1”.

You wind up with “01000001”. Let’s say that in binary code this combination of “0’s” and “1’s” equals the letter “A”. The combination “01000010” could equal “B”, and so on, through the alphabet, with a different combination of on and off capacitors equaling each letter.

“Well enough,” you may say “but there’s more things in my computer than the ABC’s. How do you account for all the rest of it?”

If you have enough banks of capacitors, you can make different combinations of “1’s” and “0’s” represent anything. Of course, it would require millions.

So, how many do you have? Look at it this way: each “1” or “0” is called a “bit”. Eight bits make a “byte”. One million bytes make a “megabyte”. If your computer has 512 megabytes of RAM, how many of those microscopic capacitors is that?

Plenty. Actually, you can get by with a lot less, though for some applications you might sacrifice speed. My first computer had only 640K of RAM, less than a megabyte, yet it performed what seemed like wonders.