File size
File size measures the size of a computer file. Typically it is measured in bytes or bits. The actual amount of disk space consumed by the file depends on the file system. The maximum file size a file system supports depends on the number of bits reserved to store size information and the total size of the file system.
Binary prefixes for powers of 210 (1,024) and decimal prefixs for powers of 103 (1,000) are both in use.[1] The International System of Quantities also allows unambiguous binary prefixes using different names based on an IEC standard, e.g., kibibyte KiB, mebibyte MiB. The traditional KB is usually binary, meaning 1,024 bytes, while the corresponding decimal kB for 1,000 bytes uses a lower case k for kilo.
With typical disk sector sizes of 512, 1,024, 2,048, or 4,096 bytes, decimal prefixes and bits are less suited to describe file systems accurately. For example, the maximal file size on FAT32 is 4 GB−1 B for a binary prefix of bytes, corresponding to 4×1024×1024×1024−1; decimal 4,294,967,295; hexadecimal FFFFFFFF; or binary 11111111111111111111111111111111 in 32 bits.[2]
| Traditional units | Decimal for comparison | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Name | Symbol | Binary | Number of bytes | Equal to | Name | IEC | Decimal | Number of bits | Equal to | |
| Kilobyte | KB | 210 | 1,024 | 1024 B | Kilobit | kbit | 103 | 1,000 | 1000 bit | |
| Megabyte | MB | 220 | 1,048,576 | 1024 KB | Megabit | Mbit | 106 | 1,000,000 | 1000 kbit | |
| Gigabyte | GB | 230 | 1,073,741,824 | 1024 MB | Gigabit | Gbit | 109 | 1,000,000,000 | 1000 Mbit | |
| Terabyte | TB | 240 | 1,099,511,627,776 | 1024 GB | Terabit | Tbit | 1012 | 1,000,000,000,000 | 1000 Gbit | |
| Petabyte | PB | 250 | 1,125,899,906,842,624 | 1024 TB | Petabit | Pbit | 1015 | 1,000,000,000,000,000 | 1000 Tbit | |
| Exabyte | EB | 260 | 1,152,921,504,606,846,976 | 1024 PB | Exabit | Ebit | 1018 | 1,000,000,000,000,000,000 | 1000 Pbit | |
| Zettabyte | ZB | 270 | 1,180,591,620,717,411,303,424 | 1024 EB | Zettabit | Zbit | 1021 | 1,000,000,000,000,000,000,000 | 1000 Ebit | |
| Yottabyte | YB | 280 | 1,208,925,819,614,629,174,706,176 | 1024 ZB | Yottabit | Ybit | 1024 | 1,000,000,000,000,000,000,000,000 | 1000 Zbit | |
References
- ↑ JEDEC Solid State Technology Association (December 2002). "Terms, Definitions, and Letter Symbols for Microcomputers, Microprocessors, and Memory Integrated Circuits" (PDF). JESD 100B.01. p. 8. Retrieved 2009-04-05.
- ↑ "Microsoft Extensible Firmware Initiative FAT32 File System Specification, FAT: General Overview of On-Disk Format". Microsoft. 2000-12-06. Retrieved 2011-07-03.