hexadecimal notation

(′hek·sə′des·məl nō′tā·shən)

(computer science) A notation in the scale of 16, using decimal digits 0 to 9 and six more digits that are sometimes represented by A, B, C, D, E, and F.

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hexadecimal number

A style of expressing numeric values similar to decimal notation except for being based on 16 rather than 10, the graphic characters for which are now usually written
0 1 2 3 4 5 6 7 8 9 A B C D E FFor example, the number 301 in the decimal system, being

= 1 × 256	+ 2 × 16	+ 13 × 1
= 1 × 162	+ 2 × 161	+ 13 × 160

is written in hexadecimal as 12D, the D standing for the 13. (All 16 graphic characters, including the six letters, are called ‘digits’ within this context.) Hexadecimal has the advantage with computers that 16 is a power of 2, and the lowest such power that can accommodate all 10 decimal digits. (Compare octal.) Since 16 = 2⁴, each hexadecimal digit equates with 4 bits, so fits conveniently precisely two digits to the now ubiquitous 8-bit byte. Some computers use hexadecimal as the base for floating-point numbers, i.e. the binary number has its fractional point moved in steps of 4 bits, the exponent applicable to 16 rather than 10. Hexadecimal notation is of particular convenience for the human study of binary data, providing a compact form for expressing binary numbers that is segmented, unlike octal, consistently with the machine bytes.