How can you tell if an object is out of bounds?

Question

C++ / C#

Good afternoon everyone and Happy New Year. Please help me find other methods for checking this condition, which is posed as a question in this topic.
There is a square, each corner has coordinates 130/130; 130/870; 870/130; 870/870 (4 sides); How to check that the given object has gone out of bounds in another way?
Here is to check the coordinates of the object and the boundaries, I know this, but what other methods are there?