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File size is a measure of how much data a computer file contains or how much storage space it is allocated. Typically, file size is expressed in units based on byte . A large value is often expressed with a metric prefix (as in megabyte and gigabyte ) or a binary prefix (as in mebibyte and gibibyte ).
File sizes are typically measured in bytes — kilobytes, megabytes, and gigabytes being usual, where a byte is eight bits. In modern textbooks one kilobyte is defined as 1,000 byte, one megabyte as 1,000,000 byte, etc., in accordance with the 1998 International Electrotechnical Commission (IEC) standard.
2 76 bits – Maximum volume and file size in the Unix File System (UFS) and maximum disk capacity using the 64-bit LBA SCSI standard introduced in 2000 using 512-byte blocks. [20] 10 23: 1.0 × 10 23 bits – increase in information capacity when 1 joule of energy is added to a heat-bath at 1 K (−272.15 °C) [21] 2 77
The byte, 8 bits, 2 nibbles, is possibly the most commonly known and used base unit to describe data size. The word is a size that varies by and has a special importance for a particular hardware context. On modern hardware, a word is typically 2, 4 or 8 bytes, but the size varies dramatically on older hardware.
The byte is the most common unit of measurement of information (megabyte, mebibyte, gigabyte, gibibyte, etc.). The decimal SI prefixes kilo, mega etc., are powers of 10. The power of two equivalents are the binary prefixes kibi, mebi, etc. Accordingly: 1 kB = 1000 bytes = 8000 bits; 1 KiB = 2 10 bytes = 1024 bytes = 8192 bits
On the other hand, a hard disk whose capacity is specified by the manufacturer as "10 gigabytes" or "10 GB", holds 10 × 10 9 = 10 000 000 000 bytes, or a little more than that, but less than 10 × 2 30 = 10 737 418 240 and a file whose size is listed as "2.3 GB" may have a size closer to 2.3 × 2 30 ≈ 2 470 000 000 or to 2.3 × 10 9 = 2 300 ...
Thus, a representation that compresses the storage size of a file from 10 MB to 2 MB yields a space saving of 1 - 2/10 = 0.8, often notated as a percentage, 80%. For signals of indefinite size, such as streaming audio and video, the compression ratio is defined in terms of uncompressed and compressed data rates instead of data sizes:
The file transfer rate in bit/s can be calculated as the file size (in bytes) divided by the file transfer time (in seconds) and multiplied by eight. As an example, the goodput or data transfer rate of a V.92 voiceband modem is affected by the modem physical layer and data link layer protocols.