"!" In c language, it is not an operator. If used before a variable, a non-operational expression is constructed, and the return result of the expression is a Boolean value (that is, only true or false). When using a variable, if it is not a Boolean data type, it will be cast to a Boolean type for reuse. For example, the integer variable 123 will be converted to true and the integer variable 0 will be converted to false.

C language: It is a general computer programming language, which is widely used. The design goal of C language is to provide a programming language that can compile and process low-level memory in a simple way, generate a small amount of machine code and run without any support of running environment.

C language operator: it is a symbol to explain specific operations and a tool to construct C language expressions. C language is extremely rich in operations. Except for control statements and input and output, almost all basic operations are handled by operators. In addition to the three common categories of arithmetic operators, relational operators and logical operators, there are some operators used to accomplish special tasks, such as bit operators.

Priority: In C language, the operation priority of operators is divided into 15 levels. 1 the highest, 15 the lowest. In an expression, a higher priority operates before a lower priority. When the operators on both sides of an operand have the same priority, they are treated according to the combination direction specified by the operator combination.