Field format (option 3)

Under option 3 output, fields can be placed in their segments in any order and with any length that conforms to the segment size restriction.

Short fields or omitted fields are padded as defined to the MFS Language utility. Each field must be preceded by a 4-byte field prefix of the same format provided by MFS for option 3 input fields, as shown in the following table.

Table 1. Format of an option 3 output segment
Output Segment 1	Output Segment 2	Output Segment 3
FL	FO	DATA

Where:

FL: The length of the field, including the 4-byte field prefix. FL consists of 2 binary bytes, which require no alignment.
FO: The relative offset of the field in the segment, based on the definition of the message to the MFS Language utility. FO consists of 2 binary bytes, which require no alignment. The relative offset of the first field defined in the segment is 4. The relative offset of the second field is 4 plus the length of the first field as defined to the MFS Language utility.

Errors in the contents of FL and FO cause unpredictable results.

Option 3 fields do not need to be in sequence in the output segment, but all fields must be contiguous in the segment; that is, the field prefix of the second field must begin in the byte beyond the first field's data. Null characters in option 3 fields have no effect on the data transmitted to the device. They are treated as any other nongraphic characters; that is, replaced with blanks.

Device control characters are invalid in output message fields. For 3270 display and SLU 2 terminals, the control characters HT, CR, LF, NL, and BS are changed to null characters. For all other devices, these control characters are changed to blanks. All other nongraphic characters (X'00' through X'3F', and X'FF') are changed to blanks before transmission. For DPM devices, control characters are permitted if GRAPHIC=NO has been specified.