This chapter has described the implementation of several aspects of the circuit editor GUI. One important note to make at this point is that the GUI maintains and validates structural information only -- it is completely unaware of the behaviour of any of the components it creates. Therefore, apart from the different graphical representation, a 2-input NAND gate is treated exactly the same by the GUI as a 2-input XOR gate despite the very different behaviours exhibited by these two components.
In order to ``give life'' to a circuit, the GUI must be interfaced with a simulator engine which can take the structural information and the input signals provided by the GUI, simulate the circuit and then return resultant output waveforms to the GUI for display. The simulator engine itself is the topic of the following chapter.