As shown in Figure 6.2, a typical ANN is made up of a hierarchy of layers, and the neurons in the networks are arranged along these layers. The neurons connected to the external environment form input and output layers. The weights are
modified to bring the network input/output behaviour into line with that of the environment.
Each neuron is an elementary information-processing unit.
It has a means of computing its activation level given the inputs and numerical weights.
To build an artificial neural network, we must decide first how many neurons are to be used and how the neurons are to be connected to form a network.
In other words, we must first choose the network architecture. Then we decide which learning algorithm to use. And finally we train the neural network, that is,we initialise the weights of the network and update the weights from a set of
training examples.Let us begin with a neuron, the basic building element of an ANN.