*background-input*to a stream that always returns EOF.
*background-query-io*to a stream that interacts with the user using CAPI prompters.
Thus when the LispWorks IDE is running, output to the standard output streams goes to the
mp:*background-standard-output*, and can be viewed in the
tab of the Listener and Editor windows, and the Output Browser tool. Trying to read from *standard-input* once the environment is running returns EOF. Using *query-io* causes on-screen prompting.
Processes that are created by CAPI for an interface while the IDE is running rebind the standard input, output and query I/O streams to themselves (so setting them in these processes does not change the global value). This does not happen on processes that are not created by CAPI, and does not happen when the LispWorks IDE is not running, in particular in delivered applications. When the LispWorks IDE is running, the output to standard output stream on other processes will still go by default to the
*background-output* is set to it.
In LispWorks 6.1 and earlier versions, CAPI processes in the LispWorks IDE bound the output streams to
mp:*background-standard-output*, the standard input to a stream that returns EOF and *QUERY-IO* to a stream that interacts with the user using CAPI prompters. Hence, for these processes, the default behavior has not changed. However input and output on other processes was going to/from the
cl:*terminal-io* by default, which caused various problems. The main purpose of these variables is to fix these problems.
LispWorks User Guide and Reference Manual - 13 Feb 2015