In electronics, it is sometimes necessary to change the shape of a waveform. Sine waves may have to be changed to square waves, rectangular waveforms may have to be changed to pulse waveforms, and pulse waveforms may have to be changed to square or rectangular waveforms. Waveforms can be analyzed by two methods. Analyzing a waveform by its amplitude per unit of time is called a time-domain analysis. Analyzing
a waveform by the sine waves that make it up is called a frequency-domain analysis. This concept assumes that all periodic waveforms are composed of sine waves.