electronist said:
my question is that if a signal is shown to me in abook ithen how do i say whether it is a power signal or a energy signal
If you see a waveform in a book, 95% of the time it's either voltage or current. That is neither power nor energy.
Rarely will you see power graphed out, but it does have meaning in some contexts. Far more rarely will you see energy. Maybe you'd see it in regards to battery discharge, but even then it would be amp-hrs and not energy.
But, silly observation- any graph should list the units, so just read them. Power is in watts. Energy is in watt-hrs, kilowatt-hrs, Joules.