C function call by value

C function

To thetraditional values of parameters passed to call thefunction, copy the actual values of the parameters to the formal parameters of the function. In this case, a modified form of the parameters within the function will not affect the actual parameters.

By default, C languagecall-by-waysto pass parameters. Generally, this means that the code within the function does not change the actual parameters used to call the function. Functionswap () is defined as follows:

/* 函数定义 */
void swap(int x, int y)
{
   int temp;

   temp = x; /* 保存 x 的值 */
   x = y;    /* 把 y 赋值给 x */
   y = temp; /* 把 temp 赋值给 y */
  
   return;
}

Now, let us by passing actual arguments to call the functionswap ():

#include <stdio.h>
 
/* 函数声明 */
void swap(int x, int y);
 
int main ()
{
   /* 局部变量定义 */
   int a = 100;
   int b = 200;
 
   printf("交换前，a 的值： %d\n", a );
   printf("交换前，b 的值： %d\n", b );
 
   /* 调用函数来交换值 */
   swap(a, b);
 
   printf("交换后，a 的值： %d\n", a );
   printf("交换后，b 的值： %d\n", b );
 
   return 0;
}

When the above code is compiled and executed, it produces the following results:

交换前，a 的值： 100
交换前，b 的值： 200
交换后，a 的值： 100
交换后，b 的值： 200

The above example shows that, although a change in the function and the value of b, but in fact, a and b values ​​are not changed.

C function