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File size measures the size of a computer file and is typically measured in bytes with a prefix. The smallest unit in computers is bit and comes from binary digit. A bit has only two digits - zero and one. The zero is also known as false (off) state and the one is known as true (on).
The bits are combined in groups in order to form larger units. The next unit larger than the bit is the byte which is formed by the combination of eight bits and can represent a value from 0 to 255 which is 2 to the power of 8 - all the possible combinations of the 8 bits that it includes.
The next larger units after the byte are named kilobyte, megabyte, gigabyte, terrabyte and so on which lead to great deal of confusion. Though the kilo prefix in the metric system means 1000 (e.g grams) in computers it means 1024 (e.g. bytes). In order to correct this mess the International Electrotechnical Commission (IEC) approved a new IEC International Standard in December 1998.
Here is a list of some of the commonly used units in the metric and their corresponding IEC binary prefixes:
|kilobyte (kB)||10 3||kibibyte (KiB)||2 10|
|megabyte (MB)||10 6||mebibyte(MiB)||2 20|
|gigabyte (GB)||10 9||gibibyte (GiB)||2 30|
|terabyte (TB)||10 12||tebibyte (TiB)||2 40|
|petabyte (PB)||10 15||pebibyte (PiB)||2 50|
|exabyte (EB)||10 18||exbibyte (EiB)||2 60|
|zettabyte (ZB)||10 21||zebibyte (ZiB)||2 70|
|yottabyte (YB)||10 24||yobibyte (YiB)||2 80|
File sizes are limited by the file system that is used and its implementation. Here are details on the common file systems:
|Maximum File Size||2 32 - 1 bytes||2 32 - 1 bytes||2 64 - 1 KB|
|Maximum Volume Size||4 GB||32 GB||2 64 clusters|
|Files Per Volume||2 16||2 22||2 32 - 1|