The s/Erik/Eric/ says "change Erik to Eric in the preceding". This
syntax is borrowed from the Unix editing tools ed and sed, but is
widely recognized by non-Unix hackers as well.

In a formula, * signifies multiplication but two asterisks in a row
are a shorthand for exponentiation (this derives from FORTRAN). Thus,
one might write 2 ** 8 = 256.

Another notation for exponentiation one sees more frequently uses the
caret (^, ASCII 1011110); one might write instead 2^8 = 256. This goes
all the way back to Algol-60, which used the archaic ASCII `up-arrow'
that later became the caret; this was picked up by Kemeny and Kurtz's
original BASIC, which in turn influenced the design of the bc(1) and
dc(1) Unix tools, which have probably done most to reinforce the
convention on Usenet. (TeX math mode also uses ^ for exponention.) The
notation is mildly confusing to C programmers, because ^ means bitwise
exclusive-or in C. Despite this, it was favored 3:1 over ** in a
late-1990 snapshot of Usenet. It is used consistently in this lexicon.

In on-line exchanges, hackers tend to use decimal forms or improper
fractions (`3.5' or `7/2') rather than `typewriter style' mixed
fractions (`3-1/2'). The major motive here is probably that the former
are more readable in a monospaced font, together with a desire to
avoid the risk that the latter might be read as `three minus
one-half'. The decimal form is definitely preferred for fractions with
a terminating decimal representation; there may be some cultural
influence here from the high status of scientific notation.

Another on-line convention, used especially for very large or very