Dracula's Definitions of Computer Memory Sizes
=== by Bob Sutherland ===
Modern Measuring Units for Computer Memory
Throughout my lifetime the field of Computer Science was very much in a state of flux as rapid advances were being made. As a result not everyone was going to be happy about using the traditional measuring units for computer memory size that I described on the previous page.
One group that would protest was the metric purists. They thought that it was pure blasphemy that we could take the prefixes of the International System of Units (SI) and apply them to powers of 2 and 1024 instead of using their sacred powers of 10 and 1000.
Another group that would protest was the inventors and manufacturers of computer memory storage devices such as CDs, DVDs, computer hard drives, computer memory sticks and flash drives. A CD has no wires so there is no logical reason to be using a system based on binary numbers when measuring a CD's memory capacity.
Finally there was the telecommunications industry who never accepted the byte as their main unit of computer memory size. They have always used bits as their main unit when measuring the speed of modems to transmit data over telephone lines, television cables and satellite signals.
The Joint Electron Device Engineering Council Solid State Technology Association (JEDEC), the International Electrotechnical Commission (IEC) and the International Organization for Standardization (ISO) are groups that have tried to create standard sets of computer memory unit names and letter symbols that they hoped everyone would adopt and follow. Unfortunately most people have probably never heard of these standardization committees and their decisions. As a result their suggested lists of computer memory unit names have just added confusion to the whole situation.
Here are the current lists of computer memory sizes. You will probably find that many large companies in the computer and telecommunications industries are using one of these lists. The problem then becomes trying to figure out which list they are using. Are the advertising and engineering departments within a company using the same list?
| Unit Name | Symbol | |||
|---|---|---|---|---|
| Bit | is the smallest unit of computer memory size. | |||
| Byte | = 8 bits | |||
| Kilobyte | kB | 103 bytes | 10001 bytes | = 1000 bytes |
| Megabyte | MB | 106 bytes | 10002 bytes | = 1000 kilobytes |
| Gigabyte | GB | 109 bytes | 10003 bytes | = 1000 megabtyes |
| Terabyte | TB | 1012 bytes | 10004 bytes | = 1000 gigabytes |
| Petabyte | PB | 1015 bytes | 10005 bytes | = 1000 terabytes |
| Exabyte | EB | 1018 bytes | 10006 bytes | = 1000 petabytes |
| Zettabyte | ZB | 1021 bytes | 10007 bytes | = 1000 exabytes |
| Yottabyte | YB | 1024 bytes | 10008 bytes | = 1000 zettabytes |
| Unit Name | Symbol | |||
|---|---|---|---|---|
| Bit | is the smallest unit of computer memory size. | |||
| Byte | = 8 bits | |||
| kibibyte | KiB | 210 bytes | 10241 bytes | = 1024 bytes |
| mebibyte | MiB | 220 bytes | 10242 bytes | = 1024 kibibytes |
| gibibyte | GiB | 230 bytes | 10243 bytes | = 1024 mebibytes |
| tebibyte | TiB | 240 bytes | 10244 bytes | = 1024 gibibytes |
| pebibyte | PiB | 250 bytes | 10245 bytes | = 1024 tebibytes |
| exbibyte | EiB | 260 bytes | 10246 bytes | = 1024 pebibytes |
| zebibyte | ZiB | 270 bytes | 10247 bytes | = 1024 exbibytes |
| yobibyte | YiB | 280 bytes | 10248 bytes | = 1024 zebibytes |
| Unit Name | Symbol | |||
|---|---|---|---|---|
| Bit | is the smallest unit of computer memory size. | |||
| Kibibit | Kibit | 210 bits | 10241 bits | = 1024 bits |
| Mebibit | Mibit | 220 bits | 10242 bits | = 1024 kibibits |
| Gibibit | Gibit | 230 bits | 10243 bits | = 1024 mebibits |
| Tebibit | Tibit | 240 bits | 10244 bits | = 1024 gibibits |
| Pebibit | Pibit | 250 bits | 10245 bits | = 1024 tebibits |
| Exbibit | Eibit | 260 bits | 10246 bits | = 1024 pebibits |
| Zebibit | Zibit | 270 bits | 10247 bits | = 1024 exbibits |
| Yobibit | Yibit | 280 bits | 10248 bits | = 1024 zebibits |
| Unit Name | Symbol | |||
|---|---|---|---|---|
| Bit | is the smallest unit of computer memory size. | |||
| Kilobit | kbit | 103 bits | 10001 bits | = 1000 bits |
| Megabit | Mbit | 106 bits | 10002 bits | = 1000 kilobits |
| Gigabit | Gbit | 109 bits | 10003 bits | = 1000 megabits |
| Terabit | Tbit | 1012 bits | 10004 bits | = 1000 gigabits |
| Petabit | Pbit | 1015 bits | 10005 bits | = 1000 terabits |
| Exabit | Ebit | 1018 bits | 10006 bits | = 1000 petabits |
| Zettabit | Zbit | 1021 bits | 10007 bits | = 1000 exabits |
| Yottabit | Ybit | 1024 bits | 10008 bits | = 1000 zettabits |
Exponent Charts
The Binary charts are based on wires and powers of two. They can also be expressed as powers of 1024.
The Metric charts use powers of 1000 rather than powers of 1024 to create alternative sets of computer memory size units.
Here are some exponent charts that will allow you to compare the difference in using powers of 1024 or powers of 1000.
| 2n | 1024m | value |
|---|---|---|
| 210 | 10241 | = 1,024 |
| 220 | 10242 | = 1,048,578 |
| 230 | 10243 | = 1,073,741,824 |
| 240 | 10244 | = 1,099,511,627,776 |
| 250 | 10245 | = 1,125,899,906,842,624 |
| 260 | 10246 | = 1,152,921,504,606,846,976 |
| 270 | 10247 | = 1,180,591,620,717,411,303,424 |
| 280 | 10248 | = 1,208,925,819,614,629,174,706,176 |
| 10n | 1000m | name | value |
|---|---|---|---|
| 103 | 10001 | thousand | = 1000 |
| 106 | 10002 | million | = 1,000,000 |
| 109 | 10003 | billion | = 1,000,000,000 |
| 1012 | 10004 | trillion | = 1,000,000,000,000 |
| 1015 | 10005 | quadrillion | = 1,000,000,000,000,000 |
| 1018 | 10006 | quintillion | = 1,000,000,000,000,000,000 |
| 1021 | 10007 | sextillion | = 1,000,000,000,000,000,000,000 |
| 1024 | 10008 | septillion | = 1,000,000,000,000,000,000,000,000 |