Tell me more ×  I am trying to understand the Simulink
(continuous) transfer function. In the documentation for the
transfer function block, it indicates that it has a direct
feedthrough characteristic when the numerator and denominator
have the same length.  The direct the feedthrough
characteristic, according to the documentation, indicates that
the output is controlled directly by the input (and not by state
variables).  I do not understand how is it possible to implement
a transfer function whose numerator and denominator have the
same degree (greater than zero) without using state variables or
previous input/output values to calculate the associated
derivatives.   Here is the line of thought that led me to this
question:  I would like to implement a C++ code that represents
a linear system with a transfer function. For this
implementation I will use an input x(t) and calculate an output
y(t). Let's say that the transfer function of this system is
G(s). I can the write it as Y(s) = G(s) * X(s).  Moreover,