As you will learn in Data Manipulation subject later, it is convenient to design main memory systems in which the total number of cells is a power of two. In turn, the size of the memories in early computers were often measured in 1024 (2^10) cell units. Since 1024 is close to the value 1000, many in the computing community adopted the prefix kilo in reference to this unit. That is, the term kilobyte (KB) was used to refer to 1024 bytes. Thus, a machine with 4096 memory cells was said to have a 4KB memory (4096 = 4 * 1024). As memories became larger, this terminology grew to include the prefixes mega for 1.048,576 (which is 2^20) and giga for 1,073,741,824 (which is 2^30), and units such as MB (megabyte) and GB (gigabyte) became popular.
Unfortunately, this application of prefixes represents a misuse of terminology because these prefixes are already used in other fields in reference to units that are powers of ten. For example, when measuring distance, kilometer refers to 1000 meters, and when measuring radio frequencies, megahertz refers to 1,000,000 hertz. To make matters even worse, some manufactures of computer equipment have mixed the two sets of terminology by using KB to refer to 1024 bytes but using MB to mean an even 1000KB (which is 1,024,000). Needless to say, these discrepancies have led to confusion and misunderstanding over the years.
To clarify matters, a proposal has been made to reserve the prefixes kilo, mega, and giga for units that are powers of ten, and to introduce the new prefixes kibi (short for kilobinary and abbreviated (Ki) in reference to the corresponding units that are powers of two. Under the system, the term kibibyte (KiB) would refer to 1024 bytes, whereas kilobyte (KB) would refer to 1000 bytes. Whether these prefixes become a part of the popular vernacular remains to be seen. For now, the traditional, “misuse” of the prefixes kilo, mega, and giga remains ingrained in the computing community when referring to main memory, and thus we will follow this tradition in our study when referring to data storage. However, the proposal prefixes kibi, megi, and gibi do represent an attempt to solve a growing problem, and one would be wise to interpret terms such as kilobyte and megabyte with caution in the future.
Recommend Reading:
Wikipedia : Binary Prefix
Coding Horror : Dude, Where’s My 4 Gigabytes of RAM?
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