User's Manual

XEROX LASER PRINTING SYSTEMS TAPE FORMATS MANUAL 3-2
Identification segment
The identification segment is a logical record used by GRASP. It
consists of a length byte (byte 0), a flag byte (byte 1), and
identification data used only by GRASP.
• The length byte contains the length of the identification
segment, including the length byte, flag byte, and identification
data.
• Bit 0 of the flag byte is set to one if the current data block
contains a line-up record. This line-up record, if present,
appears as the first logical data record in the block.
Data records
The logical data records consist of three fields.
• Field one contains a one-byte binary value which specifies the
length of field three. If zero is specified, the end of logical
records in the current physical record is indicated.
• Field two contains a one-byte code which, after turning off bit
five, should be used as the IBM System 360/370 (1403) printer
carriage control code.
• Field three is the print line data. The length of the data is
specified in field one.
GRASP tapes are single file tapes ending with a single tape mark.
Multiple reel tapes are signified by an ending tape mark coinciding
with an EOT reflector.
Line-up records
Line-up records conform to the field three format mentioned
previously. The length byte of the line-up record includes the length
of the message identifier and the length of the message text. To
locate the message text, scan the record for a hexadecimal 15
(X'15'). The text of the message begins with the character
immediately following the hexadecimal 15. The channel control word
in the line-up record is the code for a printer “no operation” (NOP).
Physical record size
The physical record size for each block of data on a GRASP tape is
equal to the GRASP disk buffer size. This buffer size is specified at
GRASP generation time and must be obtained from the user
installation's software support group.