One of the key concepts of I/O routing is the use of logical names. Ls allow reference to an I/O device without having to understand the details of the implementation of the reference. Many functions in CLIPS make use of logical names. A logical name can be either a symbol, a number, or a string. Several logical names are predefined by CLIPS and are used extensively throughout the CLIPS code. These are
Name Description
stdin The default for all user inputs. The read and readline functions read from if is specified as the logical name.
stdout The default for all user outputs. The format and printout functions send output to if t is specified as the logical name.
The CLIPS prompt is sent to this logical name.
All informational messages are sent to this logical name.
Requests to display CLIPS information, such as facts or rules, are sent to this logical name.
All error messages are sent to this logical name.
All warning messages are sent to this logical name.
All watch information is sent to this logical name (with the exception of compilations which is sent to wdialog).
Any of these logical names may be used anywhere a logical name
is expected.