IBM SC33-1683-02 - Manual (Page 331)

OPTION(addr,len)
addr The data address as {namea | (Ra) | aliteral}:
namea
The name of a location containing the data address
(Ra) A register containing the data address
aliteral
An address constant literal; for example: A(data).
len The data length as {namel | (Rn) | expression}:
namel The name of a location containing a binary fullword giving
the data length in bytes
(Rn) A register, the contents of which specify in fullword binary
the number of bytes of data
expression
A decimal integer, or any arithmetic expression, including
symbolic values, valid in assembler language; for example:
L'AREA ; L'AREA+10 ; L'AREA+X'22' ; SYMB/3+20 .
buffer-descriptor
Represents a source of both the data address and the maximum data
length fields. Parts of the buffer-descriptor are also reserved to act as
receiving fields for output information. A buffer-descriptor can be either a
single value or a multiple value. The following is the single-value form:
OPTION(bufdname)
bufdname
The name of a buffer-descriptor. A group of four contiguous
fullwords, in which:
v The first word contains the address of the data (input).
v The second word is reserved to receive the current length in
bytes of the data, as a fullword binary value (output).
v The third word contains the maximum length in bytes of the data,
as a fullword binary value (input).
v The fourth word is reserved for use by the XPI.
Register notation is not accepted for this single-value form.
The following is the multiple-value form:
OPTION(addr,maxlen,*)
addr The data address as {namea | (Ra) | aliteral}:
namea
The name of a location containing the data address
(Ra) A register containing the data address
aliteral
An address constant literal, for example, A(data).
the XPI functions
Chapter 3. The user exit programming interface (XPI) 299