This is just two operators added together. "=" is an assignment operator "!" Logical non-operators, logical operators generally regard their operands as conditional expressions, and the return result is Bool type: evaluate their operands first, and if the result is 0, the condition is false; Otherwise it is true, and the priority is "!" . Before "=", for example, there is the following formula int I；; ; I =! 5; How to understand this? 1. According to operator priority,! Before =2. First of all, 5 acts as! Operand of, evaluate! The result of 5 is bool type false3. Then the fake hermit is converted to int type, which is 04. So the value in I is the integer 0.