A device may generate code for a caller element of a first graphical model and a called element of a second graphical model by generating a first function and a second function. The first function may represent an interface between the caller element and the called element. The first function may include a first input argument corresponding to an input variable and a first output argument corresponding to an output variable. The second function may represent an underlying function of the called element. The underlying function may include the input variable passed from the caller element and the output variable. The underlying function may further include an internal input variable and an internal output variable. The second function may include second input arguments corresponding to the input variable and the internal input variable, and may include second output arguments corresponding to the output variable and the internal output variables.