Atari 400 Technical Reference Manual page 61

Printer Handler (P:)
The Printer device is a write-only device with a Handler that
supports the following CIa functions:
OPEN
CLOSE
PUT CHARACTERS
PUT RECORD
GET STATUS
The Printer Handler can produce the following error statuses:
$8A-90 -- SIO error set (see Appendix C).
The Printer Handler is one of the resident handlers, and
therefore has a set of device vectors starting at location E430.
CIO Function Descriptions
The device-specific characteristics of the standard CIO functions
are detailed below:
OPEN
The device name is P. The Handler ignores any device number and
filename specification, if included.
CLOSE
The Handler writes any data remalnlng in its buffer to the
printer device, with trailing blanks to fill out the line.
PUT CHARACTERS and PUT RECORD
The Handler accepts print data in the following format:
7
o
+-+-+-+-+-+-+-+-+
ATASCII
+-+-+-+-+-+-+-+-+
The only ATASCII control code of any significance to the Handler
is the EOL character. The printer device ignores bit 7 of every
data byte and prints a sub set of the remaining 128 codes. (see
Appendix
Q
for the printer character set).
The Handler supports the following print option:
OPERATING SYSTEM C016555 -- Section 5
76