C 中的参数传递 - 指针、地址、别名 [英] Parameter Passing in C - Pointers, Addresses, Aliases

问题描述

有人可以解释一下C中参数传递的区别吗?根据教授笔记有4种不同的参数传递方式

Could someone please explain the difference between parameter passing in C please? According to professor notes there are 4 different ways to pass parameters

1. 按价值调用
2. 按地址调用(指针)
3. 别名调用
4. 全局变量/静态变量

如果你能举个例子，我将不胜感激，你的工作也会受到赞扬.

If you could please give an example, I would greatly appreciate that, and your work would be commended.

推荐答案

1. 价值调用

将值作为参数传递给函数.如果函数修改了变量，实际变量不会改变.

Passing the value to a function as a parameter. If the function modifies the variable, the actual variable won't get changed.

void fun1(int myParam)
{
    myParam = 4;
}

void main()
{
    int myValue = 2;
    fun1(myValue);
    printf("myValue = %d",myValue);
}

myValue 将始终为 2.

按地址调用(指针)

void fun1(int *myParam)
{
    *myParam = 4;
}
void main()
{
    int myValue = 2;
    fun1(&myValue);
    printf("myValue = %d",myValue);
}

这里我们将myValue的地址传递给fun1.所以 myValue 的值在 main() 的末尾将是 4.

Here we are passing the address of myValue to fun1. So the value of myValue will be 4 at the end of main().

别名调用

根据我的理解，C 中没有别名.应该是C++引用机制.

There is no alias in C as per my understanding. It should be the C++ reference mechanism.

全局变量/静态变量

全局变量和静态变量是存储在公共位置的变量，可由调用者和被调用者函数访问.所以调用者和被调用者都可以访问和修改它们.

Global and static variables are variables stored in a common places, accessible by the caller and callee functions. So both caller and callee will be able to access and modify them.

int myValue = 2;
void fun1()
{
    myValue = 4;
}
void main()
{
    myValue = 2
    fun1();
    printf("myValue = %d",myValue);
}

如您所料，main() 末尾的 myValue 的值将是 4.

As you can guess, the value of myValue will be 4 at the end of main().

希望有帮助.

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