Classification of signals

Classification of signals:-
On the basis on nature and Characteristics in the time-domain, the signals are broadly classified into two groups as continuous-time signals and discrete-time signals but signals are classified in seven parts all parts containing two type of signals. these are as followings...

1. Continuous and Discrete-time signals.
2. Even and Odd signals.
3. Periodic and Unperiodic signals.
4. Deterministic and Random signals.
5. Energy and Power signals.
6. Casual and Non-casual signals.
7. Analog and Digital signals.

Description of all these signals are below.....

1. Continuous-Time signals:- A signal which is defined continuously with the independent variable (time) is called Continuous-Time signal. to write the Continuous-Time signal we enclose the symbol t in parentheses ( ). So continuous_time signal can be written as x_i(t). Examples of Continuous-Time signals are Audio signal as a function of time, atmospheric pressure and altitude.
2. Discrete-Time Signals:- According to the name Discrete-Time signal is defined only at discrete times, and consequently, for discrete-time signal, the independent variable takes on only a discrete set of values. In other words, A discrete-time signal is defined only at certain time instants. for discrete time signal, the amplitude between two instants is not defined. It is defined as x[ n ]. Example of Discrete-time signal- stock market index, money withdrawal from bank account, etc.
3. Even Signals:- A Even signal is that type of signal which satisfy symmetry in the time domain. This type of signal is identical about origin in X-Y graph. Example of even signal is cosine wave or cosine signal.
x (t) = x (-t)
4. Odd Signals:- An Odd signal is a type of signal which satisfy Anti-symmetry in the time domain. This type of signal is not identical about the origin in the X-Y graph. Example of Odd signal is sine wave or sine signal.
x(-t) = -x (t)

5. Periodic signals:- periodic sgnals repeat certain time period itself. a continuous time signal x(t) is said to be periodic if and only if it satisfy the condition
 x (t) = x (t+T)
example:- sine wave, cosine wave, etc

6. Unperiodic Signals:- A Unperiodic signal is said to be unperiodic if it does not repeat itself. it does not satisfy the condition
x (t+T) ≠ x (t)

7. Deterministic signals:- deterministic signals are those signal which can be completely specified in time either in mathematical form or a graphical form. deterministic signals are regular.

8. Random signals:- Random signals are also known as Non-deterministic signals. a signal, whose value can not be predicted precisely but are known in terms of probabilistic description such as mean value, mean squared value and so on, is referred to Random signals. they are always found in random in nature.

9. Energy signals:- In energy signal, total energy of the signal is finite. these signals are time limited. Unperiodic and deterministic signals are energy signals. average power in energy signal is zero.
0<E<∞
P=0

10. Power Signals:- in power signal, the average power of the signal is finite. these signal exist for infinite time. periodic signals and random signals are power signals. Total energy of the power signal is infinite.
0<P<∞
E=∞