PLL is a linear phase-locked loop control system analysis program, useful for analyzing and or predicting the behaviour of a given phase-locked loop. PLL is capable of calculating open and closed loop gain (magnitude), open loop phase and error responses as a function of frequency, the closed loop transient (time domain) response for a given input excitation and the closed loop SSB phase noise spectral density for the given system. The program includes a built-in graphics capability and operates on pull down menu system. The system requirements are: IBM PCs/XTs/ATs or compatibles running DOS 3.0 or higher. It requires a system with graphic capabilities, and will work with both CGA, EGA and Hercules graphics cards/monitors, with no "system configuration" installment procedure necessary.