PWM converters have been widely applied for power processing and they are typically the stems of other types of converters, such as quasi-resonant and multi-resonant converters. Development of the PWM converters has been spanning over a century, starting from the buck converter. The well-known PWM converters include buck, boost, buck-boost, Ćuk, SEPIC, Zeta, Z-source, quasi-Z-source, etc. Many attempts have been proposed to develop these converters based mostly on canonical cell concepts and by introducing extra LC filters to the cells. This paper presents an extended application of the Layer and Graft schemes, which is based on converter manipulation approach, to decode the PWM converters operated in either DCM or CCM. The PWM converters therefore can be derived systematically according to the codes or the input-to-output transfer gains. Decoding the PWM converters provides readers a physical connection between transfer gains and converter topologies, and a comprehensive understanding of the evolution of the PWM converters from the original converter, the buck converter. Moreover, in this paper, the Ćuk, SEPIC, and Zeta converters all with the same transfer gain of D/(1−D) are proved to be identical to the buck-boost converter with an extra LC filter.