what does dead beef mean

Question

What does the word  dead beef  mean  I read it from a interview question  It has something to do with ipv6  I figured it could be a random hex number used for examples  like  The quick brown fox jumps over the lazy dog    Is my understanding correct  Or it has more significant meaning

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http   en wikipedia org wiki Hexspeak http   www urbandictionary com define php term dead 3Abeef   Dead beef  is a very popular sentence in programming  because it is built only from letters a-f  which are used in hexadecimal notation  Colons in the beginning and in the middle of the sentence make this sentence a  theoretically  valid IPv6 address

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People normally use it to indicate dummy values  I think that it primarily was used before the idea of NULL pointers

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Since IPv6-Adresses are written in Hex-notation you can use  Hexspeak   numbers 0-9 and letters a-f  in Adresses   There are a number of words you can use as valid adresses to better momorize them   If you ping6 www facebook com -n you will get something like  2a03 2880 f01c 601 face b00c 0 1    Here are some examples     affe    Affe - German for Monkey - seen at a vlan for management board   1bad babe    one bad babe - seen at a smtp-honeypot   badc ab1e    bad cable - seen as subnet for a unsecure vlan   da7a    Data - seen for fileservers   d1a1    Dial - seen for VPN Dial-In

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The value of 0xDEADBEEF has three practical benefits  mostly for older systems  Old assembler C hacks  like me  would use it to fill unallocated memory to coax out memory issues  Also  it s a pun of the slang term  dead meat   The programmer is dead meat if DEADBEEF winds up in his pointers  I congratulate the guy who first thought of using the value DEADBEEF  It s clever in many ways   As for practical reasons  firstly  it s more noticeable in a hex memory dump because it actually spells words as opposed to random hex values   Secondly  if the value winds up in a pointer  it s more likely to induce a memory out-of-range fault  An address of DEADBEEF was out of the address range of systems  we re talking last century systems now  regardless of the system s endian   Thirdly  it is more likely to induce a fault on systems that require even boundary pointer values for accessing 16 32 64-bit data  The value is more likely to fault because both of the 16 bit values  DEAD  BEEF  are odd

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It s a magic number used in various places because it also happens to be readable in English  making it stand out   There s a partial list on Wikipedia

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It was used as a pattern to store in memory as a series of hex bytes  0xde  0xad  0xbe  0xef   You could see if memory was corrupted because of hardware failure  buffer overruns  etc

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It s a made up expression using only the letters A-F  often used when a recognisable hexadecimal number is required  Some systems use it for various purposes such as showing memory which has been freed and should not be referenced again  In a debugger this value showing up could be a sign that you have made an error  From Wikipedia      0xDEADBEEF   dead beef   is used by IBM RS 6000 systems  Mac OS on 32-bit PowerPC processors and the Commodore Amiga as a magic debug value  On Sun Microsystems  Solaris  it marks freed kernel memory  On OpenVMS running on Alpha processors  DEAD BEEF can be seen by pressing CTRL-T    The number 0xDEADBEEF is equal to the less recognisable decimal number 3735928559  unsigned  or -559038737  signed

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It is also used for debugging purposes   Here is a handy list of some of these values   http   en wikipedia org wiki Magic number  28programming 29 Magic debug values

[ipv6] what does "dead beef" mean?

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