Dark Horse Programmer--the function of "dark Horse video note" C Language Foundation

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1. When to define a function: Add a common new feature

2. function definition Format return value type function name (formal argument list) {function Body}

3. Defining a function requires something clear 1> a meaningful function name 2> function parameter and return value selection

4. Note Points for parameters

   1:   1. Formal parameters: A parameter that is followed by a function name when defining a function, for short, a formal parameter

   2:   2. Actual parameters: Invoke the specific data passed in by the function, referred to as argument

   3:   3. The number of arguments must be equal to the number of parameters

   4:   4. A variable with the same parameters cannot be defined inside the function body

   5:   5. If the base data type is a function parameter, it is purely a value pass, modifying the value of a function's internal parameter without affecting the value of the outer argument

   6:   6. A function can have no formal parameter, or it can have an infinite number of parameters

The role of 5.return:

   1:   1> Exit function

   2:   2> Returns a specific value to the function caller

   3:   return value Note point

   4:   1> void represents no return value

   5:   2> If the return value type is not explicitly stated, the default is to return the int type

   6:   3> Even if the return value type is explicitly declared, no value can be returned

   7:   By default, the C language does not allow the same name as two functions

6. Steps to define a function

   1:  1> A meaningful name based on function

   2:  2> Determining the number of formal parameters of a function

   3:  3> Determining the return value of a function

7. Other precautions

   1:  1. By default, the name of a function is not allowed

   2:   2. Functions cannot be nested defined

   3:   3. Functions cannot be defined repeatedly, but can be declared repeatedly

   4:   4. If there is a function declaration, there is no definition of the function

   5:   1> compile can pass, because the compiler will only detect syntax is not reasonable, and does not detect the function has no definition

   6:   2> link error, because the link will detect whether the function is defined

Dark Horse Programmer--the function of "dark Horse video note" C Language Foundation