Convert string from Unicode to the specified encoding. The result is a sequence of bytes (i.e., a byte array) that represents the converted string. Each byte is stored in the lower 8-bits of a Unicode character. If encoding is not specified, the current system encoding is used.
(ZB ...and what then? How to convert such "byte array" into "ordinary string", which uses chosen ISO-encoding - can be encoding system - and which uses single-byte characters?)
(DKF: Depends what you want to do really, yes? It's useful with binary format's a and A conversions, and you can communicate it externally over channels that are using the iso8859-1 encoding. Or that you configure to be -translation binary or -encoding binary. To be clear, “byte arrays” are strings where the characters are all from the range U+000000–U+0000FF; they also happen to have a more efficient internal representation, but that's not very important, a fact that you should ignore.)
Example of an encoding with "non-null" 0 character: GSM 03.38 encoding