For Historical Reasons, Opcode Value 186 is not Used.

I run across obscure references from time to time, and they have a tendency to stick in my mind, like part of a pattern that needs to be matched.  As perfect as an abstraction as mathematics may appear to some, it carries its own set of special cases and exceptions.  We assume that these are naturally occurring and just accept them at face value.  It is not very useful to try to figure out why Pi is not a round number.  It is what it is.

  The domain of computer languages and software carries its own set of special cases and exceptions, but often these are the result of human conditions.  And in carrying out whatever pursuits we are engaged in, they are accepted and we say “it is what it is.”  Following is a brief catalog of numbers, mostly with a computer related historical description, but some with related cultural references:

186  (oxBA)-Java opcode which was not used in the first Java virtual machine, for historical reasons.

3:16 – Lecture and Book by Don Knuth, author of the Art of Computer Programming.

0xCAFEBABE – Magic number which appears at the start of every Java class file (bytecode).  Note the presence of 0xBA in 0xCAFEBABE, in the third byte position.

0xCAFEDEAD – Rumored to be the originally desired magic number for Java class files, as the developers were fans of the Grateful Dead. It had already been used for other things, so CafeBabe was used instead.  Note that Java 1.0 was released January 23, 1996, 167 days after the death of Grateful Dead guitarist Jerry Garcia.

0x504B – Magic number at the begining of every ZIP format file.  These are the hex codes for ASCII characters ‘PK’ initials of  Phil Katz, the author of the original zip compression program.

0x4D5A – Magic number at the beginnng of every DOS executable program.  These are the hex codes for ASCII characters ‘MZ’, initials of the developer of the file format, Mark Zbikowski.

8675309 – Seen in many, many more oscure contexts for computing.  From unlock codes for games, to causing a mode change for Microsoft’s WebTV, and various others.  This was Jenny’s Phone Number, in the hit song by Tommy Tutone.

420 – A cultural reference to cannibas. 

404 – Page Not Found Error Code in HTML

2600 – The frequency originally used by AT&T to signal a ready state for a long distance phone line.  Also the same frequency which was produced by a toy whistle which was given as a toy surprise in Captain Crunch Cereal in the mid 1960’s.  As an added curiosity, to no one except for myself, I happen to have the home printer, HP Photosmart 2600.

90125 – The original catalog number of the Yes album, by the same name.

9:15 – Time of the train referenced in The Who’s Quadraphenia in the song by the same name.

90210 – The zip code for a Bevery Hills neighborhood in which a popular 1990’s tv series was based.

The appearance of numbers and codes like those listed is frequent.  The presence of codes and oddities in the digital domain offer an endless supply of curiosities.  The crossing of domains has become more and more commonplace as computers and digital electronics settle into their place in our culture.  Phone numbers become song titles, and song titles become codes in computer file formats, and will continue to do so.  And most of the time, “they are what they are.”


3 Responses to For Historical Reasons, Opcode Value 186 is not Used.

  1. Terry says:

    Don’t forget

    64738 – Used to restart the Commodore 64 ( sys64738 )
    49152 – used to start many programs on the c64 ( sys49152 )

  2. howardscholz says:

    Oh, yes. C64 people could recite those in their sleep. I was a TRS-80 guy, and missed the C64 fun.

  3. 3D0 – Address to jump to return to Basic on the Apple II.

    0407 – First two words of UNIX PDP-11 binaries, a branch around the header.

    0411 – First two words of a Split I&D PDP-11 binary, again a branch around the header.

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