Parse each line by character location

[Tyler]

Hello All:

I hope this is the right place to ask, but I am trying to come up with
a way to parse each line of a file. Unfortunately, the file is neither
comma, nor tab, nor space delimited. Rather, the character locations
imply what field it is.

For example:

The first ten characters would be the record number, the next
character is the client type, the next ten characters are a volume,
and the next three are order type, and the last character would be an
optional type depending on the order type.

The lines are somewhat more complicated, but they work like that, and
not all have to be populated, in that they may contain spaces. For
example, the order number may be 2345, and it is space padded at the
beginning of the line, and other might be zero padded in the front.
Imagine I have a line:

______2345H0000300000_NC_

where the underscores indicate a space. I then want to map this to:

2345,H,0000300000,NC,

In other words, I want to preserve ALL of the fields, but map to
something that awk could easily cut up afterwords, or open in a CSV
editor. I am unsure how to place the commas based on character
location.

Any ideas?