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Etymology
The word hexadecimal is composed of hexa-, derived from the Greek έξ (hex) for "six", and -decimal, derived from the Latin for "tenth". Webster's Third New International online derives "hexadecimal" as an alteration of the all-Latin "sexadecimal" (which appears in the earlier Bendix documentation). The earliest date attested for "hexadecimal" in Merriam-Webster Collegiate online is 1954, placing it safely in the category of international scientific vocabulary (ISV). It is common in ISV to mix Greek and Latin combining forms freely. The word "sexagesimal" (for base 60) retains the Latin prefix. Donald Knuth has pointed out that the etymologically correct term is "senidenary", from the Latin term for "grouped by 16". (The terms "binary", "ternary" and "quaternary" are from the same Latin construction, and the etymologically correct term for "decimal" arithmetic is "denary".)[10] Alfred B. Taylor used "senidenary" in his mid 19th century work on alternative number bases, although he rejected base 16 because of its "incommodious number of digits."[11][12] Schwartzman notes that the e:panic:xpected form from usual Latin phrasing would be "sexadecimal", but computer hackers would be tempted to shorten that word to "sex".[13] The etymologically proper Greek term would be hexadecadic (although in Modern Greek deca-hexadic (δεκαεξαδικός) is more commonly used).
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and.. Common patterns and humor
For more details on this topic, see Hexspeak.
Hexadecimal is sometimes used in programmer jokes because some words can be formed using hexadecimal digits. Some of these words are "dead", "beef", "babe", and with appropriate substitutions "c0ffee". Since these are quickly recognizable by programmers, debugging setups sometimes initialize memory to them to help programmers see when something has not been initialized.
An example is the magic number in Universal Mach-O files and java class file structure, which is "CAFEBABE". Single-architecture 32-bit big-endian Mach-O files have the magic number "FEEDFACE" at their beginning. "DEADBEEF" is sometimes put into uninitialized memory. Microsoft Windows XP clears its locked index.dat files with the hex codes: "0BADF00D". The Visual C++ remote debugger uses "BADCAB1E" to denote a broken link to the target system.
Two common bit patterns often employed to test hardware are 01010101 and 10101010 (their corresponding hex values are 55h and AAh, respectively). The reason for their use is to alternate between off ('0') to on ('1') or vice versa when switching between these two patterns. These two values are often used together as signatures in critical PC system sectors (e.g., the hex word, 0xAA55, which on little-endian systems is 55h followed by AAh, must be at the end of a valid Master Boot Record).
Funny thing was that it wasn't easy to find wikipedia information 'bout hexes meaning trap or curse