51 single chip microcomputer error-prone

• After 51 single-chip microcomputer is powered on, the pin is high by default;
• When 51 single-chip I/O port outputs high level, it is close to VCC and can be calculated by VCC
• while (expression). If the expression is not 0, it is true, then the statement is executed, otherwise the while statement is jumped out.
• When keil software is debugged, after setting a breakpoint, the line where the breakpoint is located will not be executed, and it will stop when it reaches it.
• IIC transmits the highest bit first;
• Serial communication transmits the lowest bit first;