HoA is correct, because the o does not start a "significant" word. (Your English teacher will tell you that a word is "significant" for capitalisation purposes unless it is an article, a coordinating conjunction, or a short preposition. I forget whether "short" in this context means <5 letters or <=5 letters.) It is common for abbreviations to capitalise only the words that start a significant word: e.g., ComIntern, CoBOL[1].

We don't write PERL, of course, because computer technical words are (usually) case-sensitive. This is a special rule, but that's normal in English. Nouns in the field of music follow a different declension if they end in "o"; words and abbreviations imported unchanged from Latin, unlike words imported from all other languages, are typeset in italics, except for mathematical terms imported from Latin (e.g., QED), which are not; et cetera, ad infinitum.

The case-sensitivity in computer words allows for a significant amount of disambiguation: hence the distinction between Perl and perl, the lack of any confusion between BIND and activities with rope, and so on. The rule is universal among people who understand computer stuff in general, which is an ever-growing percentage of the population, and I am confident that it will become a permanent special rule like the others listed. But yes, people who don't know will continue to write "PERL", "Email", "pianoes", "ect.", confuse e.g. with i.e., and just generally write like wankers.

  1. CoBOL does not follow hackish rules because (like RPG) it is not a hacker language. 
for(unpack("C*",'GGGG?GGGG?O__\?WccW?{GCw?Wcc{?Wcc~?Wcc{?~cc'
.'W?')){$j=$_-63;++$a;for$p(0..7){$h[$p][$a]=$j%2;$j/=2}}for$
p(0..7){for$a(1..45){$_=($h[$p-1][$a])?'#':' ';print}print$/}

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In reply to Re: Perl and Unix versus PERL and UNIX by jonadab
in thread Perl and Unix versus PERL and UNIX by Anonymous Monk

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