function

C Language functions need to be declared before being defined

Statement （ Form good habits , Write a function declaration ）

 return type   Function name （ parameter list ）;

Don't forget the semicolon at the end of the function declaration .

Definition

 return type   Function name （ parameter list ）
{
    
	 The body of the function ;
}

If the return value type is not specified, write void, Do not write the default return integer , No parameters can be left blank , Brackets must be written , There is no semicolon at the end of the function

Use

Write the function name like calling a library function （ Parameters ） Just go

 Function name （ Parameters ）;

Note that the parameters here are the arguments passed in by the user , The above definition is formal parameter

Function parameters and pointers

1、 Pass value

void swap(int x,int y)
{
    
	int temp;
	temp = x;
	x = y;
	y = temp;
}

Functions can be realized in the function body , But do not change the data outside the function . After calling this function x,y The value of , It is equivalent to copying the value of the parameter and exchanging the copied value
2、 Byref

void swap(int *x,int *y)
{
    
	int temp;
	temp = *x;
	*x = *y;
	*y = temp;
}

In this way, the address of the argument is passed into the function , Function directly operates on the address data , The data outside the function will change
3、 quote

void swap(int &x,int &y)
{
    
	int temp;
	temp = x;
	x = y;
	y = temp;
}

The function is the same as that of address , But a reference is equivalent to giving a variable another name , In fact, it still operates on the incoming variables
4、 Pass array

void print(int a[10])
{
    
	int i;
	for(i=0;i<10;i++)
	{
    
		printf("%d\n",a[i]);
	}
}

It's different from passing only one number , There is no such transfer method as copying the entire array , Talked about before , The array name is equivalent to its pointer , Because the array name is the address of the first element , Note the address , So if you pass in an array , It is possible to modify the value of a number in the array in the function .