How to ensure 1 byte per character

This is my first foray into character encoding, and I'm trying to
ensure that a large file is of the size that one can expect for 1 byte
per character. It is a simple text file that contains about 42
million characters. The file on the HD is 84MB. I've set encoding
and fileencoding to latin1, which the help says is 8-bit characters.
I also have fileformat=unix to ensure that line endings are only 1
byte. After writing to HD, however, the file on the HD is still 84MB.
I know that it's not due to my use of cygwin because for this very text
that I'm using to compose this message, the characters counts so match
the file size.

What else could be cause the 2x discrepancy between file size and
characte count?

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