man 3 switch

[Bruno Wolff III]

On Sat, Nov 14, 2009 at 14:50:57 -0500,
  "Steven W. Orr" <steveo at syslang.net> wrote:
> Or my personal favorite, in Fortran.
> 
>       DO 10 I = 1,100

Not to mention the easy to make typo
        DO 10 I = 1.100

It can take quite a while to figure that one out the first time it happens
to you. Especially reading crappy line printer output or the print along
the top of the cards (assuimg you had any).