1. It is technically easy to implement. It is easy to express binary digits 0 and 1 with bistable circuits            2. high reliability. In binary system, only 0 and 1 digits are used. It is not easy to make mistakes in transmission and processing, so it can guarantee the high reliability of computer.            3. The operation rules are simple. Compared with decimal number, the operation rules of binary number are much simpler, which not only simplifies the structure of the calculator, but also improves the operation speed.

2.different use of string determine its meaning.