我认为，它们被声明为函数的参数。

I think, they were declared like parameters of the function.

你在哪里看到它们在这个函数中声明了？

Where do you see them declared in this function ?

	T show()
{
	return(x>y)?x:y;
}

可能你应该使用 a 和 b 而不是？

[更新]

May be you should use a and b instead ?
[Update]

它们被声明用于设置函数。

为什么我不能使用其他变量？

they are declared for set function.
and why can't i use other variables?

它们仅在set函数中声明为set函数。

[更新]

在 show 中，您可以使用 a 和 b 因为你在类定义中声明了它们。

They declared in set function for set function only.
[Update]
In show, you can use a and b because you declared them in class definition.

class myMax{
 	T a,b;

您要显示的代码，

The code that you are showing,

T show()
{
	return(x>y)?x:y;
}

无效，通过查看类定义（看看成员！）。您只定义了a和b作为类中的属性，x和y未赋予任何类型，因此在给定范围内没有定义。

Is invalid, by looking at the class definition (have a look at the members!). You have defined only a and b to be properties in the class, x and y are not given to be of any type, and thus no defined in the given scope.

只有a和b工作。

这是因为a和b被定义为属性（类别 T 类中的（成员）。这完美地执行。因为编译器知道要使用的类型以及在作用域中定义它们的位置（作为成员）。



解决这个问题的方法就是使用a和b名称。不要使用x和y;因为这也需要更改类定义！

That is because a and b are defined as properties (members) in your class of type T. That executes perfectly. Because compiler knows what type to use and where they are defined in the scope (as the members).

Solution to this problem is to just use the a and b names. Don't use the x and y; because that would require to change the class definition too!

不是解决方案，而是链接到好的讲座。



开始C书，C语言是C ++的始祖。大多数C适用于C ++。

C编程语言 - ***，免费的百科全书 [ ^ ]

https://hassanolity.files.wordpress.com/2013/11/the_c_programming_language_2.pdf [ ^ ]

http://www.ime.usp.br/~pf/Kernighan-Ritchie/C- Programming-Ebook.pdf [ ^ ]



C ++编程语言 [ ^ ]



[更新]

学习一些分析方法， Dijkstra自上而下方法是一个好的开始。

它将帮助您设备结构化算法。

https://en.wikipedia.org/wiki/Top-down_and_bottom-up_design [ ^ ]

https://en.wikipedia.org/wiki/Structured_programming [ ^ ]

https://en.wikipedia.org/wiki/Edsger_W._Dijkstra [ ^ ]

https： //www.cs.utexas.edu/users/EWD/ewd03xx/EWD316.PDF [ ^ ]

Not a solution, but links to good lectures.

Start with the C book, C language is the ancestor of C++. Most of C apply to C++.
The C Programming Language - Wikipedia, the free encyclopedia[^]
https://hassanolity.files.wordpress.com/2013/11/the_c_programming_language_2.pdf[^]
http://www.ime.usp.br/~pf/Kernighan-Ritchie/C-Programming-Ebook.pdf[^]

C++ Programing Language[^]

[Update]
Learn some analyze method, Dijkstra Top-Down method is a good start.
It will help you to device structured algorithms.
https://en.wikipedia.org/wiki/Top-down_and_bottom-up_design[^]
https://en.wikipedia.org/wiki/Structured_programming[^]
https://en.wikipedia.org/wiki/Edsger_W._Dijkstra[^]
https://www.cs.utexas.edu/users/EWD/ewd03xx/EWD316.PDF[^]