This attribute is primarily intended to be used as a RETURN-only attribute. It returns the number of lines present in the PRINTER widget. In SET mode, the VALID LINES attribute may be used to eliminate unwanted lines.
For example, if you set the value of VALID LINES to 10, the "oldest" 10 lines will remain and the most recently appended lines will be lost.
To clear the PRINTER widget, set the value of VALID LINES to 0. If you attempt to set VALID LINES to a value greater than the total number of lines, a "Value out of range" error will result.
