IBM Professional Series User Manual page 347

Rx+l
Rx+ 1 must point to the buffer in virtual storage where
CP is to return the command response.
Ry+l
Ry+ 1 must specify, in bytes, the length of the buffer.
This value must not exceed 8192.
If the command response is to be returned in a buffer, CP
sets a condition code and returns information as follows:
condition code 0
The request was successful. The Rx + 1 register points to
the buffer that contains the command response. The
Ry + 1 register specifies the length of the response.
condition code 1
The request was unsuccessful. The response does not fit
into the buffer. The Ry+ 1 register contains a value that
specifies how many bytes of the response would not fit
into the buffer.
When CP returns to a program executing a DIAGNOSE 8
instruction, the length value that was supplied in register Ry
is replaced by the CP completion code value. This value is
zero if the CP console function was successfully executed. If
an error occurred, the completion code is the numeric value
expressed in the message describing the error. For example,
if error message DMKCFM045E is issued, CP sets a
completion code of 45.
If the user has not specified a command response buffer,
error messages and informational messages are generated
according to the current values established by SET EMSG
and SET IMSG commands.
If a command response buffer is used, error and
informational messages are always put into the buffer instead
of being written to the console. Each line of the response is
followed by a new line character (X'15'). If the buffer is not
long enough to contain all of the response lines, only as
many complete lines as can fit into the buffer are supplied, so
the last character written into the response buffer by CP is
always a new line character. Any unused portion of the
A-8 VM/PC Users Guide