Why the input lines of multiplexer do not appear in the truth table with logic values?

In a multiplexer, the input lines themselves do not appear in the truth table with logic values because the truth table primarily represents the relationship between the select lines and the output based on the input combinations. The inputs are considered fixed values that are selected based on the binary state of the select lines. The truth table typically shows how the output responds to different combinations of select line values rather than detailing the static input states. This focus simplifies the representation of the multiplexer’s functionality.