Under this standard, the first character of each printable record (line) determines vertical spacing, as follows:
blank carriage return 0 two carriage returns 1 Formfeed + overprint - three carriage returns (IBM extension)
All other characters are discarded, and empty lines behave as though they have a leading blank.
asa interprets these characters.
1 inability to write on stdout or to read an input file
2 bad argument
Exit status values chosen from MKS toolkit.
The carriage-control '-' is an IBM extension. Perhaps the default should ignore it and there should be a '-i' option to interpret it.
NWG/RFC 189, Appendix C