Arduino Technical Specs:
6. Analog I/O Pins(模拟输入/输出针脚) 8个
7. Digital I/O Pins(数字输入/输出引脚) 14个
Analog vs Digital：
Analog(模拟) and digital(数字) signals(信号) are used to(被用于) transmit information(传输信息), usually through electric signals(通过电子信号).
In both these technologies(这些技术), the information, such as(例如) any audio or video(音频或视频), is transformed into electric signals(被转换为电子信号).
The difference between(之间的区别) analog and digital technologies is that in(在于) analog technology, information is translated into(翻译为，转换为) electric pulses of varying amplitude（变幅电脉冲）.
In digital technology, translation of information is into binary format（二进制格式） (zero or one，0或1的表示) where each bit is representative of (代表，表示)two distinct (不同的)amplitudes（振幅）.
An Analog signal is any continuous signal(连续的信号)
A digital signal uses discrete(离散的) (discontinuous，不连续的) values
简单来说，将灯打开关闭这种开关(0/1)表示就是数字信号
将灯逐渐从暗到明，再从明到暗具有连续的过程的表示就是模拟信号(具有周期性的，一般呈现sin曲线)
