How much input and output needed for demultiplexer?

A demultiplexer (also known as a demux) is a device that takes a single input line and routes it to one of several digital output lines. A demultiplexer of 2^n outputs has n select lines, which are used to select which output line to send the input.

For example, a 1:4 demultiplexer would have 1 input line, 4 output lines, and 2 select lines. The select lines determine where the input should be sent by turning on one of the output lines.

So, the number of inputs and outputs needed for a demultiplexer depends on the number of output lines you want. The number of select lines (n) will determine the number of output lines (2^n). The demultiplexer will always have one input line.