Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Frame Dependent
GV_PYTHON_FRAMEParameter: Reset on Frame 0
GV_PYTHON_RESETParameter: Code
GV_PYTHON_CODEParameter: Open Python Editor
GV_PYTHON_OPENEDITORParameter: On
GV_PYTHON_ONParameter: Integer
IN_LONGParameter: Integer
OUT_LONGParameter: String
IN_STRINGParameter: String
OUT_STRINGParameter: Float
IN_REALParameter: Float
OUT_REALParameter: Vector
IN_VECTORParameter: Vector
OUT_VECTORParameter: Matrix
IN_MATRIXParameter: Matrix
OUT_MATRIXParameter: Time
IN_BASETIMEParameter: Time
OUT_BASETIMEParameter: Bool
IN_BOOLParameter: Bool
OUT_BOOLParameter: Link
IN_LINKParameter: Link
OUT_LINKParameter: Filename
IN_FILENAMEParameter: Filename
OUT_FILENAMEParameter: Gradient
IN_GRADIENTParameter: Gradient
OUT_GRADIENTParameter: InExcludeList
IN_INEXCLUDELISTParameter: InExcludeList
OUT_INEXCLUDELISTParameter: SplineData
IN_SPLINEDATAParameter: SplineData
OUT_SPLINEDATAParameter: SoundData
IN_SOUNDDATAParameter: SoundData
OUT_SOUNDDATA