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Representation

Written representation

Using 0â€“9 and Aâ€“F

{{Hexadecimal table}}In contexts where the base is not clear, hexadecimal numbers can be ambiguous and confused with numbers expressed in other bases. There are several conventions for expressing values unambiguously. A numerical subscript (itself written in decimal) can give the base explicitly: 15910 is decimal 159; 15916 is hexadecimal 159, which is equal to 34510. Some authors prefer a text subscript, such as 159decimal and 159hex, or 159d and 159h.In linear text systems, such as those used in most computer programming environments, a variety of methods have arisen:
• In URIs (including URLs), character codes are written as hexadecimal pairs prefixed with %:weblink where %20 is the space (blank) character, ASCII code point 20 in hex, 32 in decimal.
• In XML and XHTML, characters can be expressed as hexadecimal numeric character references using the notation &xcode;, where the x denotes that code is a hex code point (of 1- to 6-digits) assigned to the character in the Unicode standard. Thus &x2019; represents the right single quotation mark (â€™), Unicode code point number 2019 in hex, 8217 (thus &8217; in decimal).WEB,weblink The Unicode Standard, Version 7, Unicode, October 28, 2018,
• In the Unicode standard, a character value is represented with U+ followed by the hex value, e.g. U+20AC is the Euro sign (â‚¬).
• Color references in HTML, CSS and X Window can be expressed with six hexadecimal digits (two each for the red, green and blue components, in that order) prefixed with : white, for example, is represented FFFFFF.WEB,weblink Hexadecimal web colors explained, CSS allows 3-hexdigit abbreviations with one hexdigit per component: FA3 abbreviates FFAA33 (a golden orange: {{color box|FA3}}).
• {{anchor|_nix}}Unix (and related) shells, AT&T assembly language and likewise the C programming language (and its syntactic descendants such as C++, C, D, Java, JavaScript, Python and Windows PowerShell) use the prefix 0x for numeric constants represented in hex: 0x5A3. Character and string constants may express character codes in hexadecimal with the prefix x followed by two hex digits: 'x1B' represents the Esc control character; "x1B[0mx1B[25;1H" is a string containing 11 characters (plus a trailing NUL to mark the end of the string) with two embedded Esc characters.The string "x1B[0mx1B[25;1H" specifies the character sequence Esc [ 0 m Esc [ 2 5 ; 1 H Nul. These are the escape sequences used on an ANSI terminal that reset the character set and color, and then move the cursor to line 25. To output an integer as hexadecimal with the printf function family, the format conversion code %X or %x is used.
• In MIME (e-mail extensions) quoted-printable encoding, characters that cannot be represented as literal ASCII characters are represented by their codes as two hexadecimal digits (in ASCII) prefixed by an equal to sign =, as in Espa=F1a to send "EspaÃ±a" (Spain). (Hexadecimal F1, equal to decimal 241, is the code number for the lower case n with tilde in the ISO/IEC 8859-1 character set.)
• In Intel-derived assembly languages and Modula-2,WEB, Modula-2 - Vocabulary and representation,weblink Modula -2, 1 November 2015, hexadecimal is denoted with a suffixed H or h: FFh or 05A3H. Some implementations require a leading zero when the first hexadecimal digit character is not a decimal digit, so one would write 0FFh instead of FFh
• Other assembly languages (6502, Motorola), Pascal, Delphi, some versions of BASIC (Commodore), GameMaker Language, Godot and Forth use \$ as a prefix: \$5A3.
• Some assembly languages (Microchip) use the notation H'ABCD' (for ABCD16). Similarly, Fortran 95 uses Z'ABCD'.
• Ada and VHDL enclose hexadecimal numerals in based "numeric quotes": 165A3. For bit vector constants VHDL uses the notation x"5A3".The VHDL MINI-REFERENCE: VHDL IDENTIFIERS, NUMBERS, STRINGS, AND EXPRESSIONS
• Verilog represents hexadecimal constants in the form 8'hFF, where 8 is the number of bits in the value and FF is the hexadecimal constant.
• The Smalltalk language uses the prefix 16r: 16r5A3
• PostScript and the Bourne shell and its derivatives denote hex with prefix 16: 165A3. For PostScript, binary data (such as image pixels) can be expressed as unprefixed consecutive hexadecimal pairs: AA213FD51B3801043FBC...
• Common Lisp uses the prefixes x and 16r. Setting the variables read-baseWEB, read-base variable in Common Lisp,weblink and print-baseWEB, print-base variable in Common Lisp,weblink to 16 can also be used to switch the reader and printer of a Common Lisp system to Hexadecimal number representation for reading and printing numbers. Thus Hexadecimal numbers can be represented without the x or 16r prefix code, when the input or output base has been changed to 16.
• MSX BASIC,MSX is Coming â€” Part 2: Inside MSX Compute!, issue 56, January 1985, p. 52 QuickBASIC, FreeBASIC and Visual Basic prefix hexadecimal numbers with &H: &H5A3
• BBC BASIC and Locomotive BASIC use & for hex.BBC BASIC programs are not fully portable to Microsoft BASIC (without modification) since the latter takes & to prefix octal values. (Microsoft BASIC primarily uses &O to prefix octal, and it uses &H to prefix hexadecimal, but the ampersand alone yields a default interpretation as an octal prefix.
• TI-89 and 92 series uses a 0h prefix: 0h5A3
• ALGOL 68 uses the prefix 16r to denote hexadecimal numbers: 16r5a3. Binary, quaternary (base-4) and octal numbers can be specified similarly.
• The most common format for hexadecimal on IBM mainframes (zSeries) and midrange computers (IBM System i) running the traditional OS's (zOS, zVSE, zVM, TPF, IBM i) is X'5A3', and is used in Assembler, PL/I, COBOL, JCL, scripts, commands and other places. This format was common on other (and now obsolete) IBM systems as well. Occasionally quotation marks were used instead of apostrophes.
• Donald Knuth introduced the use of a particular typeface to represent a particular radix in his book The TeXbook.Donald E. Knuth. The TeXbook (Computers and Typesetting, Volume A). Reading, Massachusetts: Addisonâ€“Wesley, 1984. {{isbn|0-201-13448-9}}. The source code of the book in TeX {{webarchive|url=https://web.archive.org/web/20070927224129weblink |date=2007-09-27 }} (and a required set of macros CTAN.org) is available online on CTAN. Hexadecimal representations are written there in a typewriter typeface: 5A3
• Any IPv6 address can be written as eight groups of four hexadecimal digits (sometimes called hextets), where each group is separated by a colon (:). This, for example, is a valid IPv6 address: 2001:0db8:85a3:0000:0000:8a2e:0370:7334; this can be abbreviated as 2001:db8:85a3::8a2e:370:7334. By contrast, IPv4 addresses are usually written in decimal.
• Globally unique identifiers are written as thirty-two hexadecimal digits, often in unequal hyphen-separated groupings, for example {3F2504E0-4F89-41D3-9A0C-0305E82C3301}.
There is no universal convention to use lowercase or uppercase for the letter digits, and each is prevalent or preferred in particular environments by community standards or convention.

History of written representations

missing image!
- Bruce Martin hexadecimal notation proposal.png -
Bruce Alan Martin's hexadecimal notation proposal
The use of the letters A through F to represent the digits above 9 was not universal in the early history of computers.
• During the 1950s, some installations{{which|date=August 2017}} favored using the digits 0 through 5 with an overline to denote the values 10â€“15 as {{overline|0}}, {{overline|1}}, {{overline|2}}, {{overline|3}}, {{overline|4}} and {{overline|5}}.
• The SWAC (1950) and Bendix G-15 (1956) computers used the lowercase letters u, v, w, x, y and z for the values 10 to 15.
• The ILLIAC I (1952) computer used the uppercase letters K, S, N, J, F and L for the values 10 to 15.
• The Librascope LGP-30 (1956) used the letters F, G, J, K, Q and W for the values 10 to 15.
• The Honeywell Datamatic D-1000 (1957) used the lowercase letters b, c, d, e, f, and g whereas the Elbit 100 (1967) used the uppercase letters B, C, D, E, F and G for the values 10 to 15.
• The Monrobot XI (1960) used the letters S, T, U, V, W and X for the values 10 to 15.
• The NEC parametron computer {{ill|NEAC 1103|ja|NEAC}} (1960) used the letters D, G, H, J, K (and possibly V) for values 10â€“15.BOOK, NEC Parametron Digital Computer Type NEAC-1103, Nippon Electric Company Ltd., Tokyo, Japan, Cat. No. 3405-C, 1960,weblink 2017-05-31, no,weblink" title="web.archive.org/web/20170531112850weblink">weblink 2017-05-31,
• The Pacific Data Systems 1020 (1964) used the letters L, C, A, S, M and D for the values 10 to 15.
• New numeric symbols and names were introduced in the Bibi-binary notation by Boby Lapointe in 1968. This notation did not become very popular.
• Bruce Alan Martin of Brookhaven National Laboratory considered the choice of Aâ€“F "ridiculous". In a 1968 letter to the editor of the CACM, he proposed an entirely new set of symbols based on the bit locations, which did not gain much acceptance.JOURNAL, Letters to the editor: On binary notation, Bruce Alan, Martin, Associated Universities Inc., Communications of the ACM, 11, 10, October 1968, 658, 10.1145/364096.364107,
• Soviet programmable calculators Ð‘3-34 (1980) and similar used the symbols "âˆ’", "L", "C", "Ð“", "E", " " (space) for the values 10 to 15 on their displays.{{cn|date=August 2017}}
• Seven-segment display decoder chips used various schemes for outputting values above nine. The Texas Instruments 7446/7447/7448/7449 and 74246/74247/74248/74249 use truncated versions of "2", "3", "4", "5" and "6" for the values 10 to 14. Value 15 (1111 binary) was blank.BCD-TO-SEVEN-SEGMENT DECODERS/DRIVERS: SN54246/SN54247/SN54LS247, SN54LS248 SN74246/SN74247/SN74LS247/SN74LS248, March 1988, March 1974, SDLS083, Texas Instruments,weblink 2017-03-30, no,weblink" title="web.archive.org/web/20170329223343weblink">weblink 2017-03-29, [â€¦] They can be used interchangeable in present or future designs to offer designers a choice between two indicator fonts. The '46A, '47A, 'LS47, and 'LS48 compose the 6 and the 9 without tails and the '246, '247, 'LS247, and 'LS248 compose the 6 and the 0 with tails. Composition of all other characters, including display patterns for BCD inputs above nine, is identical. [â€¦] Display patterns for BCD input counts above 9 are unique symbols to authenticate input conditions. [â€¦],

Verbal and digital representations

There are no traditional numerals to represent the quantities from ten to fifteen â€“ letters are used as a substitute â€“ and most European languages lack non-decimal names for the numerals above ten. Even though English has names for several non-decimal powers (pair for the first binary power, score for the first vigesimal power, dozen, gross and great gross for the first three duodecimal powers), no English name describes the hexadecimal powers (decimal 16, 256, 4096, 65536, ... ). Some people read hexadecimal numbers digit by digit like a phone number, or using the NATO phonetic alphabet, the Joint Army/Navy Phonetic Alphabet, or a similar ad hoc system.(File:Hexadecimal-counting.jpg|right|thumb|Hexadecimal finger-counting scheme)Systems of counting on digits have been devised for both binary and hexadecimal.Arthur C. Clarke suggested using each finger as an on/off bit, allowing finger counting from zero to 102310 on ten fingers.BOOK, Clarke, Arthur, Pohl, Frederik, The Last Theorem, 2008, Ballantine, 978-0007289981, 91, Another system for counting up to FF16 (25510) is illustrated on the right.

Signs

The hexadecimal system can express negative numbers the same way as in decimal: âˆ’2A to represent âˆ’4210 and so on.Hexadecimal can also be used to express the exact bit patterns used in the processor, so a sequence of hexadecimal digits may represent a signed or even a floating point value. This way, the negative number âˆ’4210 can be written as FFFF FFD6 in a 32-bit CPU register (in two's-complement), as C228 0000 in a 32-bit FPU register or C045 0000 0000 0000 in a 64-bit FPU register (in the IEEE floating-point standard).

Conversion

Binary conversion

Most computers manipulate binary data, but it is difficult for humans to work with the large number of digits for even a relatively small binary number. Although most humans are familiar with the base 10 system, it is much easier to map binary to hexadecimal than to decimal because each hexadecimal digit maps to a whole number of bits (410).This example converts 11112 to base ten. Since each position in a binary numeral can contain either a 1 or a 0, its value may be easily determined by its position from the right:
• 00012 = 110
• 00102 = 210
• 01002 = 410
• 10002 = 810
Therefore:{|
| = 810 + 410 + 210 + 110
| = 1510
With little practice, mapping 11112 to F16 in one step becomes easy: see table in Written representation. The advantage of using hexadecimal rather than decimal increases rapidly with the size of the number. When the number becomes large, conversion to decimal is very tedious. However, when mapping to hexadecimal, it is trivial to regard the binary string as 4-digit groups and map each to a single hexadecimal digit.This example shows the conversion of a binary number to decimal, mapping each digit to the decimal value, and adding the results.{|| = 26214410 + 6553610 + 3276810 + 1638410 + 819210 + 204810 + 51210 + 25610 + 6410 + 1610 + 210
| = 38792210
Compare this to the conversion to hexadecimal, where each group of four digits can be considered independently, and converted directly:{|
|00102
5 align="center" B align="center" 216
5EB5216
The conversion from hexadecimal to binary is equally direct.

Other simple conversions

Although quaternary (base 4) is little used, it can easily be converted to and from hexadecimal or binary. Each hexadecimal digit corresponds to a pair of quaternary digits and each quaternary digit corresponds to a pair of binary digits. In the above example 5 E B 5 216 = 11 32 23 11 024.The octal (base 8) system can also be converted with relative ease, although not quite as trivially as with bases 2 and 4. Each octal digit corresponds to three binary digits, rather than four. Therefore we can convert between octal and hexadecimal via an intermediate conversion to binary followed by regrouping the binary digits in groups of either three or four.

Division-remainder in source base

As with all bases there is a simple algorithm for converting a representation of a number to hexadecimal by doing integer division and remainder operations in the source base. In theory, this is possible from any base, but for most humans only decimal and for most computers only binary (which can be converted by far more efficient methods) can be easily handled with this method.Let d be the number to represent in hexadecimal, and the series hihiâˆ’1...h2h1 be the hexadecimal digits representing the number.
1. i â† 1
2. hi â† d mod 16
3. d â† (d âˆ’ hi) / 16
4. If d = 0 (return series hi) else increment i and go to step 2
"16" may be replaced with any other base that may be desired.The following is a JavaScript implementation of the above algorithm for converting any number to a hexadecimal in String representation. Its purpose is to illustrate the above algorithm. To work with data seriously, however, it is much more advisable to work with bitwise operators.function toHex(d) {
var r = d % 16;
if (d - r == 0) {
}
}function toChar(n) {
const alpha = "0123456789ABCDEF";
return alpha.charAt(n);
}

Image:Hexadecimal multiplication table.svg|right|thumb|A hexadecimal multiplication tablemultiplication tableIt is also possible to make the conversion by assigning each place in the source base the hexadecimal representation of its place value and then performing multiplication and addition to get the final representation.That is, to convert the number B3AD to decimal one can split the hexadecimal number into its digits: B (1110), 3 (310), A (1010) and D (1310), and then get the final result by multiplying each decimal representation by 16p, where p is the corresponding hex digit position, counting from right to left, beginning with 0. In this case we have {{math|B3AD {{=}} (11â€‰Ã—â€‰163) + (3â€‰Ã—â€‰162) + (10â€‰Ã—â€‰161) + (13â€‰Ã—â€‰160)}}, which is 45997 base 10.

Tools for conversion

Most modern computer systems with graphical user interfaces provide a built-in calculator utility, capable of performing conversions between various radices, in general including hexadecimal.In Microsoft Windows, the Calculator utility can be set to Scientific mode (called Programmer mode in some versions), which allows conversions between radix 16 (hexadecimal), 10 (decimal), 8 (octal) and 2 (binary), the bases most commonly used by programmers. In Scientific Mode, the on-screen numeric keypad includes the hexadecimal digits A through F, which are active when "Hex" is selected. In hex mode, however, the Windows Calculator supports only integers.

Real numbers

Rational numbers

As with other numeral systems, the hexadecimal system can be used to represent rational numbers, although repeating expansions are common since sixteen (10hex) has only a single prime factor (two):{| style="text-align:right;" border=0 cellspacing=0 cellpadding=3
1/2 > = 0.8
= 0.{{overline|5}}
1/4 > = 0.4
= 0.{{overline|3}}
= 0.2{{overline|A}}
= 0.{{overline|249}}
1/8 > = 0.2
= 0.{{overline|1C7}}
= 0.1{{overline|9}}
= 0.{{overline|1745D}}
= 0.1{{overline|5}}
= 0.{{overline|13B}}
= 0.1{{overline|249}}
= 0.{{overline|1}}
1/10 > = 0.1
= 0.{{overline|0F}}
| 2
1/2 {{color2}}| 0.5| 0.8 {{color2}} 1/2
| 3
1/3 {{color3}} 0.3333... = 0.{{overline|3}} 0.5555... = 0.{{overline|5}} {{color3}} 1/3
| 4
1/4 {{color2}}| 0.25| 0.4 {{color2}} 1/4
| 5
1/5 {{color5}}| 0.2 0.{{overline|3}} {{color5}} 1/5
| 6
1/6 {{color2}}, {{color3}} 0.1{{overline|6}} 0.2{{overline|A}} {{color2}}, {{color3}} 1/6
| 7
1/7 7 0.{{overline|142857}} 0.{{overline|249}} 7 1/7
| 8
1/8 {{color2}}| 0.125| 0.2 {{color2}} 1/8
| 9
1/9 {{color3}} 0.{{overline|1}} 0.{{overline|1C7}} {{color3}} 1/9
| 10
1/10 {{color2}}, {{color5}}| 0.1 0.1{{overline|9}} {{color2}}, {{color5}} 1/A
| 11
1/11 {{color11}} 0.{{overline|09}} 0.{{overline|1745D}} B 1/B
| 12
1/12 {{color2}}, {{color3}} 0.08{{overline|3}} 0.1{{overline|5}} {{color2}}, {{color3}} 1/C
| 13
1/13 13 0.{{overline|076923}} 0.{{overline|13B}} D 1/D
| 14
1/14 {{color2}}, 7 0.0{{overline|714285}} 0.1{{overline|249}} {{color2}}, 7 1/E
| 15
1/15 {{color3}}, {{color5}} 0.0{{overline|6}} 0.{{overline|1}} {{color3}}, {{color5}} 1/F
| 16
1/16 {{color2}}| 0.0625| 0.1 {{color2}} 1/10
| 17
1/17 17 0.{{overline|0588235294117647}} 0.{{overline|0F}} {{color11}} 1/11
| 18
1/18 {{color2}}, {{color3}} 0.0{{overline|5}} 0.0{{overline|E38}} {{color2}}, {{color3}} 1/12
| 19
1/19 19 0.{{overline|052631578947368421}} 0.{{overline|0D79435E5}} 13 1/13
| 20
1/20 {{color2}}, {{color5}}| 0.05 0.0{{overline|C}} {{color2}}, {{color5}} 1/14
| 21
1/21 {{color3}}, 7 0.{{overline|047619}} 0.{{overline|0C3}} {{color3}}, 7 1/15
| 22
1/22 {{color2}}, {{color11}} 0.0{{overline|45}} 0.0{{overline|BA2E8}} {{color2}}, B 1/16
| 23
1/23 23 0.{{overline|0434782608695652173913}} 0.{{overline|0B21642C859}} 17 1/17
| 24
1/24 {{color2}}, {{color3}} 0.041{{overline|6}} 0.0{{overline|A}} {{color2}}, {{color3}} 1/18
| 25
1/25 {{color5}}| 0.04 0.{{overline|0A3D7}} {{color5}} 1/19
| 26
1/26 {{color2}}, 13 0.0{{overline|384615}} 0.0{{overline|9D8}} {{color2}}, D 1/1A
| 27
1/27 {{color3}} 0.{{overline|037}} 0.{{overline|097B425ED}} {{color3}} 1/1B
| 28
1/28 {{color2}}, 7 0.03{{overline|571428}} 0.0{{overline|924}} {{color2}}, 7 1/1C
| 29
1/29 29 0.{{overline|0344827586206896551724137931}} 0.{{overline|08D3DCB}} 1D 1/1D
| 30
1/30 {{color2}}, {{color3}}, {{color5}} 0.0{{overline|3}} 0.0{{overline|8}} {{color2}}, {{color3}}, {{color5}} 1/1E
| 31
1/31 31 0.{{overline|032258064516129}} 0.{{overline|08421}} 1F 1/1F
| 32
1/32 {{color2}}| 0.03125| 0.08 {{color2}} 1/20
| 33
1/33 {{color3}}, {{color11}} 0.{{overline|03}} 0.{{overline|07C1F}} {{color3}}, B 1/21
| 34
1/34 {{color2}}, 17 0.0{{overline|2941176470588235}} 0.0{{overline|78}} {{color2}}, {{color11}} 1/22
| 35
1/35 {{color5}}, 7 0.0{{overline|285714}} 0.{{overline|075}} {{color5}}, 7 1/23
| 36
1/36 {{color2}}, {{color3}} 0.02{{overline|7}} 0.0{{overline|71C}} {{color2}}, {{color3}} 1/24

Irrational numbers

The table below gives the expansions of some common irrational numbers in decimal and hexadecimal.{| class="wikitable"! rowspan=2 | Number! colspan=2 | Positional representation! Decimal! Hexadecimal
Square root of 2>{{sqrt {{small>(the length of the diagonal of a unit square)}}1.414213562373095048}}...| 1.6A09E667F3BCD...
Square root of 3>{{sqrt {{small>(the length of the diagonal of a unit cube)}}1.732050807568877293}}...| 1.BB67AE8584CAA...
Square root of 5>{{sqrt {{small>(the length of the diagonal of a 1Ã—2 rectangle)}}2.236067977499789696}}...| 2.3C6EF372FE95...
Golden ratio>{{mvar {{small>1=(phi, the golden ratio = {{math5}})/2}})}}1.618033988749894848}}...| 1.9E3779B97F4A...
Pi>{{mvar {{small>(pi, the ratio of circumference to diameter of a circle)}}3.141592653589793238462643}}{{val|383279502884197169399375105}}...| 3.243F6A8885A308D313198A2E03707344A4093822299F31D008...
E (mathematical constant)>{{mvar {{small>(the base of the natural logarithm)}}2.718281828459045235}}...| 2.B7E151628AED2A6B...
Thueâ€“Morse constant>{{mvar {{small>(the Thueâ€“Morse constant)}}0.412454033640107597}}...| 0.6996 9669 9669 6996...
Euler-Mascheroni constant>{{mvar {{small>(the limiting difference between the harmonic series and the natural logarithm)}}0.577215664901532860}}...| 0.93C467E37DB0C7A4D1B...

Powers

Powers of two have very simple expansions in hexadecimal. The first sixteen powers of two are shown below.{| class="wikitable"! 2x !! Value !! Value (Decimal)
| 1
| 2
| 4
| 8
| 16dec
| 32dec
| 64dec
| 128dec
| 256dec
| 512dec
10{{sub| 1024dec
11{{sub| 2048dec
12{{sub| 4096dec
13{{sub| 8192dec
14{{sub| 16,384dec
15{{sub| 32,768dec
16{{sub| 65,536dec

Cultural

Use in Chinese culture

The traditional Chinese units of measurement were base-16. For example, one jÄ«n (æ–¤) in the old system equals sixteen taels. The suanpan (Chinese abacus) can be used to perform hexadecimal calculations.

Primary numeral system

As with the duodecimal system, there have been occasional attempts to promote hexadecimal as the preferred numeral system. These attempts often propose specific pronunciation and symbols for the individual numerals.WEB
, Base 4^2 Hexadecimal Symbol Proposal
, Some proposals unify standard measures so that they are multiples of 16.WEB,weblink Intuitor Hex Headquarters, Intuitor, October 28, 2018, WEB,weblink A proposal for addition of the six Hexadecimal digits (A-F) to Unicode, Niemietz, Ricardo Cancho, October 21, 2003, October 28, 2018, BOOK,weblink Project of a New System of Arithmetic, Weight, Measure and Coins: Proposed to be called the Tonal System, with Sixteen to the Base, Nystrom, John William, Lippincott, 1862, Philadelphia, An example of unified standard measures is hexadecimal time, which subdivides a day by 16 so that there are 16 "hexhours" in a day.

Base16 (Transfer encoding)

Base16 (as a proper name without a space) can also refer to a binary to text encoding belonging to the same family as Base32, Base58, and Base64.In this case, data is broken into 4-bit sequences, and each value (between 0 and 15 inclusively) is encoded using 16 symbols from the ASCII character set. Although any 16 symbols from the ASCII character set can be used, in practice the ASCII digits '0'-'9' and the letters 'A'-'F' (or the lowercase 'a'-'f') are always chosen in order to align with standard written notation for hexadecimal numbers.There are several advantages of Base16 encoding:
• Being exactly half a byte, 4-bits is easier to process than the 5 or 6 bits of Base32 and Base64 respectively
• The symbols 0-9 and A-F are universal in hexadecimal notation, so it is easily understood at a glance without needing to rely on a symbol lookup table
• Many CPU architectures have dedicated instructions that allow access to a half-byte (otherwise known as a "Nibble"), making it more efficient in hardware than Base32 and Base64
The main disadvantages of Base16 encoding are:
• Space efficiency is only 50%, since each 4-bit value from the original data will be encoded as an 8-bit byte. In contrast, Base32 and Base64 encodings have a space efficiency of 63% and 75% respectively.
• Possible added complexity of having to accept both uppercase and lowercase letters
Support for Base16 encoding is ubiquitous in modern computing. It is the basis for the W3C standard for URL Percent Encoding, where a character is replaced with a percent sign "%" and its Base16-encoded form. Most modern programming languages directly include support for formatting and parsing Base16-encoded numbers.

References

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