A neural network is usually comprised by three layers of units (nodal points) or artificial neurons. The first layer is input layer consisting of a group of processing units which are responsible for acceptance of data imported to the network.

• 神经网络通常由三层单元(节点)或人工神经元组成。第一层即输入层，包含一组处理单元，负责接受向网络输入的数据。