Why digital signals have infinite bandwidth?

Digital signals can theoretically have infinite bandwidth because they are composed of discrete values that can switch between states at very high frequencies. Each transition between these states, particularly in pulse-width modulation or other encoding schemes, can require a significant amount of frequency to accurately represent the sharp changes. Additionally, the use of techniques like oversampling and high-frequency clock signals can introduce additional harmonics, further expanding the signal's bandwidth. However, practical limitations such as noise and physical medium constraints typically restrict the effective bandwidth in real-world applications.