Quaternary is a numeral system with four as its base. It uses the digits 0, 1, 2, and 3 to represent any real number. Conversion from binary is straightforward.

Four is the largest number within the subitizing range and one of two numbers that is both a square and a highly composite number (the other being thirty-six), making quaternary a convenient choice for a base at this scale. Despite being twice as large, its radix economy is equal to that of binary. However, it fares no better in the localization of prime numbers (the smallest better base being the primorial base six, senary).

Quaternary shares with all fixed-radix numeral systems many properties, such as the ability to represent any real number with a canonical representation (almost unique) and the characteristics of the representations of rational numbers and irrational numbers. See decimal and binary for a discussion of these properties.

Relation to other positional number systems + Numbers zero to sixty-four in standard quaternary (0 to 1000)Decimal 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Binary 0 1 10 11 100 101 110 111 1,000 1,001 1,010 1,011 1,100 1,101 1,110 1,111 Quaternary 0 1 2 3 10 11 12 13 20 21 22 23 30 31 32 33 Octal 0 1 2 3 4 5 6 7 10 11 12 13 14 15 16 17 Hexadecimal 0 1 2 3 4 5 6 7 8 9 A B C D E F Decimal 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Binary 10,000 10,001 10,010 10,011 10,100 10,101 10,110 10,111 11,000 11,001 11,010 11,011 11,100 11,101 11,110 11,111 Quaternary 100 101 102 103 110 111 112 113 120 121 122 123 130 131 132 133 Octal 20 21 22 23 24 25 26 27 30 31 32 33 34 35 36 37 Hexadecimal 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F Decimal 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 Binary 100,000 100,001 100,010 100,011 100,100 100,101 100,110 100,111 101,000 101,001 101,010 101,011 101,100 101,101 101,110 101,111 Quaternary 200 201 202 203 210 211 212 213 220 221 222 223 230 231 232 233 Octal 40 41 42 43 44 45 46 47 50 51 52 53 54 55 56 57 Hexadecimal 20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F Decimal 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 Binary 110,000 110,001 110,010 110,011 110,100 110,101 110,110 110,111 111,000 111,001 111,010 111,011 111,100 111,101 111,110 111,111 Quaternary 300 301 302 303 310 311 312 313 320 321 322 323 330 331 332 333 Octal 60 61 62 63 64 65 66 67 70 71 72 73 74 75 76 77 Hexadecimal 30 31 32 33 34 35 36 37 38 39 3A 3B 3C 3D 3E 3F Decimal 64Binary 1,000,000 Quaternary 1,000Octal 100Hexadecimal 40

Relation to binary and hexadecimal + addition table + 0 1 2 3 0 0 1 2 3 1 1 2 3 10 2 2 3 10 11 3 3 10 11 12 As with the octal and hexadecimal numeral systems, quaternary has a special relation to the binary numeral system. Each radix four, eight, and sixteen is a power of two, so the conversion to and from binary is implemented by matching each digit with two, three, or four binary digits, or bits. For example, in quaternary, 2302104 = 10 11 00 10 01 002. Since sixteen is a power of four, conversion between these bases can be implemented by matching each hexadecimal digit with two quaternary digits. In the above example, 23 02 104 = B2416

+ multiplication table × 0 1 2 3 0 0 0 0 0 1 0 1 2 3 2 0 2 10 12 3 0 3 12 21

Although octal and hexadecimal are widely used in computing and computer programming in the discussion and analysis of binary arithmetic and logic, quaternary does not enjoy the same status.

Although quaternary has limited practical use, it can be helpful if it is ever necessary to perform hexadecimal arithmetic without a calculator. Each hexadecimal digit can be turned into a pair of quaternary digits. Then, arithmetic can be performed relatively easily before converting the end result back to hexadecimal. Quaternary is convenient for this purpose, since numbers have only half the digit length compared to binary, while still having very simple multiplication and addition tables with only three unique non-trivial elements.

By analogy with byte and nybble, a quaternary digit is sometimes called a crumb.

Fractions Due to having only factors of two, many quaternary fractions have repeating digits, although these tend to be fairly simple:

Decimal basePrime factors of the base: 2, 5Prime factors of one below the base: 3Prime factors of one above the base: 11Other prime factors: 7 13 17 19 23 29 31 Quaternary basePrime factors of the base: 2Prime factors of one below the base: 3Prime factors of one above the base: 5 (=114)Other prime factors: 13 23 31 101 103 113 131 133 Fraction Prime factors ofthe denominator Positionalrepresentation Positionalrepresentation Prime factors ofthe denominator Fraction 2 0.5 0.2 2 3 0.3333... = 0. 0.1111... = 0. 3 2 0.25 0.1 2 5 0.2 0. 11 2, 3 0.1 0.0 2, 3 7 0. 0. 13 2 0.125 0.02 2 3 0. 0. 3 2, 5 0.1 0.0 2, 11 11 0. 0. 23 2, 3 0.08 0.0 2, 3 13 0. 0. 31 2, 7 0.0 0.0 2, 13 3, 5 0.0 0. 3, 11 2 0.0625 0.01 2 17 0. 0. 101 2, 3 0.0 0.0 2, 3 19 0. 0. 103 2, 50.05 0.0 2, 11 3, 7 0. 0. 3, 13 2, 11 0.0 0.0 2, 23 23 0. 0. 113 2, 3 0.041 0.00 2, 3 50.04 0. 11 2, 13 0.0 0.0 2, 31 3 0. 0. 3 2, 7 0.03 0.0 2, 13 29 0. 0. 131 2, 3, 5 0.0 0.0 2, 3, 11 31 0. 0. 133 20.031250.002 2 3, 11 0. 0. 3, 23 2, 17 0.0 0.0 2, 101 5, 7 0.0 0. 11, 13 2, 3 0.02 0.0 2, 3

Occurrence in human languages

Many or all of the Chumashan languages (spoken by the Native American Chumash peoples) originally used a quaternary numeral system, in which the names for numbers were structured according to multiples of four and sixteen, instead of ten. There is a surviving list of Ventureño language number words up to thirty-two written down by a Spanish priest ca. 1819.

The Kharosthi numerals (from the languages of the tribes of Pakistan and Afghanistan) have a partial quaternary numeral system from one to ten.

Hilbert curves Quaternary numbers are used in the representation of 2D Hilbert curves. Here, a real number between 0 and 1 is converted into the quaternary system. Every single digit now indicates in which of the respective four sub-quadrants the number will be projected.

Genetics

Parallels can be drawn between quaternary numerals and the way genetic code is represented by DNA. The four DNA nucleotides in alphabetical order, abbreviated A, C, G, and T, can be taken to represent the quaternary digits in numerical order 0, 1, 2, and 3. With this encoding, the complementary digit pairs 0↔3, and 1↔2 (binary 00↔11 and 01↔10) match the complementation of the base pairs: A↔T and C↔G and can be stored as data in DNA sequence. For example, the nucleotide sequence GATTACA can be represented by the quaternary number 2033010 (= decimal 9156 or binary 10 00 11 11 00 01 00). The human genome is 3.2 billion base pairs in length.

Data transmission Quaternary line codes have been used for transmission, from the invention of the telegraph to the 2B1Q code used in modern ISDN circuits.

The GDDR6X standard, developed by Nvidia and Micron, uses quaternary bits to transmit data.

Computing Some computers have used quaternary floating point arithmetic including the Illinois ILLIAC II (1962) and the Digital Field System DFS IV and DFS V high-resolution site survey systems.

See also Conversion between bases Moser–de Bruijn sequence, the numbers that have only 0 or 1 as their base-4 digits

References

External links

Quaternary Base Conversion, includes fractional part, from Math Is Fun Base42 Proposes unique symbols for Quaternary and Hexadecimal digits