Investigate 8.1.
What are the potential benefits of each of these prefix conventions? Why do you think there is more than one convention?
Section 8.1 Prefixes
With different variables using up different amounts of space in memory and with storing (sometimes large amounts of) data comes the need for conventions to talk about the size of different amounts of data.
In this video you’ll learn about prefixes such as exa, peta, etc.
| Prefix | Size | Reference | ||
| byte | B | 8 bits | (1) | 1 character (ASCII) |
| Kilo | KB | 1024 bytes | \((2^{10})\) | 1/4 page of text |
| Mega | MB | 1,048,576 bytes | \((2^{20})\) | 1/4 song MP3 |
| Giga | GB | 1,073,741,824 bytes | \((2^{30})\) | Old iPod |
| Tera | TB | 1.099\(\times 10^12\) bytes | \((2^{40})\) | Affordable storage |
| Peta | PB | 1.125\(\times 10^15\) bytes | \((2^{50})\) | SDSC HD |
| Exa | EB | 1.153\(\times 10^18\) bytes | \((2^{60})\) | |
| Zetta | ZB | 1.181\(\times 10^21\) bytes | \((2^{70})\) | 0.36 ZB = 1g of DNA |
| Yotta | YB | 1.209\(\times 10^24\) bytes | \((2^{80})\) | Avogadro’s Number |
It was estimated (in 2005) that the total amount of printed material in the world is about 5 EB.
Avogadro’s Number: number of carbon-12 atoms in 12 grams of carbon-12 ~ \(6 \times 10^{23}\) ~ \(2^{79}\)
1 YB = 2.01 * Avogadro’s Number
Note the difference between \(1000 = 10^3\) and \(1024 = 2^{10}\)
1999 International Electrotechnical Commission (IEC) Amendment to include new base-2 prefixes:
| Prefix | Size | |
| kibibyte | KiB | \((2^{10})\) = 1,024 bytes |
| mebibyte | MiB | \((2^{20})\) |
| gibibyte | GiB | \((2^{30})\) |
| tebibyte | TiB | \((2^{40})\) |
| pebibyte | PiB | \((2^{50})\) |
| exibyte | EiB | \((2^{60})\) |
| zebibyte | ZiB | \((2^{70})\) |
| yobibyte | YiB | \((2^{80})\) |
100 TB ~ 90.9 TiB ~ 10% error
2009: Snow Leopard --- 1kB = 1000 bytes
Check Your Understanding Check Your Understanding
1.
Find the difference between 3 Mebibyes and 3 Megabytes (in the Apple convention) and express this difference as a percentage of the 3 Megabytes. What is this percent error, rounded to the nearest whole number? Please enter the percentage number only, not the % sign.
