What is the difference between actual parameters and formal parameters in C language?

Actual parameters are the values or variables passed to a function when it is called, while formal parameters are the variables declared in the function definition to receive the values passed by the actual parameters. The main differences between actual parameters and formal parameters are as follows:

1. Definition of position: Parameters are declared when a function is defined, used to receive the values passed by arguments; Arguments are specific values or variables passed to the function when it is called.
2. Data types: The parameter and argument can be of different data types, but in a function call, the data type of the argument must match the data type of the parameter.
3. Scope: The scope of actual parameters is limited to the function call, and the value of actual parameters will be destroyed after the function is executed; the scope of formal parameters is limited to the function itself, and the value of formal parameters cannot be accessed outside the function.
4. Memory allocation: When passing actual parameters to formal parameters, a copy of the value of the actual parameter is made for the formal parameter, which is used within the function instead of the actual parameter itself.

In general, formal parameters are variables declared when defining a function, used to receive the values passed by actual parameters. The actual parameters are the specific values or variables passed to the function when called. There is a value passing relationship between formal parameters and actual parameters, where the value of actual parameters is copied to formal parameters. The formal parameters use this copied value within the function.