> CODE39 is a character oriented barcode that is alpha-numeric. I2of5 is
> numeric only. If I had to choose one from scratch I would use CODE39 it
> is easy to read, doesn't need much buffer space and easy to print on
> stick on labels. Even commercial wands are low cost. Some of the HP
> HEDS 3000 series wands are $5 or so in a surplus shop and maybe
> $75-$100 new.

Interleaved 2 of 5 is a fairly simple code which stores information in base
100; like code39, it can be processed on the fly.

Each data group consists of five marks and five spaces; the last space on one
data group ends with the first mark of the next (I forget how the barcodes
are terminated; I think with just a narrow line).  Two of the marks are
wider than the other marks; two of the spaces are wider than the other
spaces.  The five marks code one decimal digit; the five spaces code another
decimal digit.

Marks and spaces come in two widths: wide and narrow; the wide ones are about
3x the width of the narrow ones.  Inking variations may of course cause these
widths to vary; for maximum reliability, you might want to keep track of the
mark and space widths seperately and then check them against each other.

Because there are only two widths of marks and two widths of spaces, I2of5
is a fairly simple code to read.  It is also quite dense: if wide marks/spaces
are 3 pixels and narrow ones are 1 pixel, then two decimal digits can be
stored in 18 pixels.