Transistor whatis the meaning of bc in a bc 547 transistor

The first letter: A = Ge material semiconductors, B = Si material semiconductors, C = GaAs material semiconductors, R = Compound material. The second letter: A = Diode (low power, signal); B = Diode (variable capacitance)); C = Transistor (low power, audio frequency); D = Transistor (power, audio frequency); F = Transistor (low power, high frequency); L = Transistor (power, high frequency); R= control and swithching device); S = Transistor (low power, swithching); T = thyristors; U = Transistor (power, switching); X = Diode (varactor, multiplier); Y = Diode (rectifier); Z = Diode (zener). So the BC547 is a Silicon low power, audio frequency transistor. Hope that helps!