WHEN YOU TALK ABOUT YOUR COMPUTER’S memory or the size of computer files, you probably mention “megs.” This is short for “megabytes” or a million bytes. A byte is a computer programming word that refers to a specific amount of information. One byte is just about equal to one letter or one number.
This table shows you how many bytes are in a computer.
| Prefix |
Bytes |
| kilo (K) |
1,024 |
| mega (M) |
1,048,576 |
| giga (G) |
1,073,741,824 |
| tera |
1,099,511,627,776 |
| peta |
1,125,899,906,842,624 |
| exa |
1,152,921,504,606,846,976 |
| zetta |
1,180,591,620,717,411,303,424 |
| yotta |
1,208,925,819,614,629,174,706,176 |
When computers were built in the 1950s, they were so big that they were stored in rooms the size of a school cafeteria. But they were only as powerful as today’s pocket calculators, and they could only handle a few bytes at a time. By the 1980s, most computer memory was measured in kilobytes, which seemed like a lot at the time. In the 1990s, it reached megabytes. Today, we talk more and more about gigabytes. In the next few years, you’ll be hearing a lot about petabytes.
Here’s how all those numbers translate into familiar paper versions.
| 1 byte |
One letter |
| 10 bytes |
Two words |
| 100 bytes |
One long sentence |
| 1 KB |
Two paragraphs |
| 10 KB |
One page in a dictionary |
| 100 KB |
A 3 x 5 photograph |
| 1 MB |
A 250-page book |
| 10 MB |
Two copies of the complete works of Shakespeare, or two songs (MP3s) |
| 100 MB |
1 shelf of books four feet long |
| 1 GB |
An SUV filled with books |
| 100 GB |
The books on one floor of a local public library |
| 1 TB |
The paper from 50,000 trees |
| 10 TB |
All the books and letters in the U.S. Library of Congress |
It is estimated that all the printed paper created every year would equal about 2 exabytes. Another estimate is that we could store a recording of everything ever said by anybody in the history of the world in 42 zettabytes. Not that we’d want to listen to all those people all over again, but it’s nice to know that we have the power.