IEEE 1541-2021 pdf download

IEEE 1541-2021 pdf download.IEEE Standard for Prefxes for Binary Multples
2. Normative references
There are no normative references needed to implement this document. Please see Annex A for the  nformative bibliography.
3. Defi nitions
For the purposes of this document, the following terms and definitions apply. The IEEE Standards Dictionary Online should be consulted for terms not defined in this clause. 4 The definitions below include information adapted from the International Electrotechnical Vocabulary (IEV) [B3].
bit (bit): (A) A binary digit, usually given alternative values of either 0 or 1. (B) A member of a set of two elements commonly used to represent information [B3].
byte (B): (A) A group of eight bits. (B) An ordered set of eight binary digits [B3].
NOTE—Prior to the publication of ISO/IEC 80000-13 [B6], the byte was defi ned in terms of the machine’s  nderlying
native character set and was therefore not always eight bits. 5
octet (o): (A) A group of eight bits. (B) An ordered set of eight binary digits.
4. Prefi xes for binary multiples
The binary prefixes given in Table 1 shall be used to indicate multiplication by 2 10n , where n = 1, 2, 3, 4, 5, 6,7, 8.
5. SI prefi xes
The prefixes kilo, mega, giga, etc., are defined in “The International System of Units (SI)” [B1] (informally known as the “SI Brochure”) of the International Bureau of Weights and Measures (BIPM), and other international standards, to stand solely for powers of 10. Using them to stand for binary multiples, such as powers of 1024, is internationally recognized as being deprecated and shall not be used. The SI decimal prefixes shall be used only to represent powers of 10. Table 2 provides background reference information as to the relationship of the binary and SI prefixes.
6. Application of the prefi xes for binary multiples
When binary prefixes are used, the prefix name and a unit name are combined to form a single word, and similarly the prefix symbol and a unit symbol are written (without any space between symbols) to form a single symbol. Proper application of the prefi xes for binary multiples benefi ts the general public
—the wide audience of technical and non-technical persons who use computers without much concern for their construction or inner working, who would otherwise reasonably interpret mega, giga, etc., in their proper decimal sense. As well, the prefi xes for binary multiples make it possible for specialists who work in the information sciences to communicate with precision. The SI system defi nes decimal prefi xes only, not binary; however, the SI prefi xes are sometimes used where binary prefi xes would be more proper. The following three examples illustrate some of the confusion caused by misinterpreting binary and SI prefi xes.
— Example 1: The 120 mm compact disc (CD), as formatted for personal computer use, is usually advertised as containing space for 700 MB of data. However, it is actually formatted for 737.280 MB (i.e., 360 000 sectors of 2048 B each) or about 703.125 mebibytes (MiB). Thus, labeling those CDs as “700 MiB,” although rounded, would most closely represent the actual storage available and demonstrate the proper usage of binary prefi xes.
— Example 2: A USB fl ash drive is labeled as having a capacity of 64 GB. But by misusing SI decimal prefi xes as if they were binary prefi xes, a computer’s operating system notes that same USB fl ash drive as having a capacity of “59.6 GB.” Again describing the fl ash drive as having a capacity 59.6 GiB, by utilizing the correct binary prefi xes, accurately represents the bytes available.
— Example 3: A hard drive is described as having a capacity of 250 GB and as having 61 049 646 sectors of 4096 B each. The usable capacity then is 250 059 350 016 B. Yet some computer operating systems may report its capacity as “232.88 GB” and format it as “232 GB” hard drive. Thus this 250 GB hard drive has a usable capacity of 232.88 GiB, not 232.88 GB, as computer operating systems would typically describe it. Once again, the correct usage of binary prefi xes more accurately represents the bytes that can be stored on the hard drive. All three examples illustrate the diff erence between misapplying SI prefi xes for the description of storage devices versus the correct application of binary prefi xes, e.g., Ki versus k or Gi versus G. In the examples above, due to the incorrect application, the resulting diff erences in described storage capacity vary from approximately 5 to 7%.
In the third example, it can be observed that the diff erences start becoming signifi cant and are frequently misunderstood by general users. Therefore, the correct usage of binary prefi xes, as recommended by the American National Standard for Metric Practice IEEE/ASTM SI 10 [B5] (see also NIST SP 330 [B7]) is essential for accurate technical discussion in the information sciences community.IEEE 1541 pdf download.IEEE 1541-2021 pdf download