C 如何生成一个函数，该函数接收指向将被乘和除的数字的指针？

我知道我可以通过位向左移位进行乘法，向右移位进行除法，但让我困惑的是指向数字的函数（指针）的参数

void func(unsigned *u)
{
   *u >>= 1;        // do the operation on the unsigned value pointed by u.
                    // u contains the address of the object (in this case, the unsigned)
}

打电话

unsigned a = 23;
func(&a);    // pass the pointer to the variable a. After the function executes,
             // a will be changed as the operation is done on it.