The output is true if all inputs are true, otherwise the output is false.
The input connector is a vector of Boolean input signals. When a connection line is drawn, the dimension of the input vector is enlarged by one and the connection is automatically connected to this new free index (thanks to the connectorSizing annotation).
The usage is demonstrated, e.g., in example Modelica.Blocks.Examples.BooleanNetwork1.
If no connection to the input connector "u" is present, the output is set to true: y=true.