What are the differences between the concepts of white, gray, and black boxes in system analysis?

In system analysis and software testing, three main approaches to studying and verifying a system are distinguished:

• White Box — testing or analysis where the internal structure, logic, and code of the system are known. The tester has access to the source code and can create tests based on an understanding of the internal implementation.

• Black Box — an approach where the system is viewed as a "black box" without knowledge of its internal structure. Testing is based solely on input data and expected output results, without analyzing the internal code.

• Gray Box — an intermediate approach that combines elements of both white and black box testing. The tester has partial knowledge of the internal structure of the system, which allows for more effective test planning, but testing is conducted from the perspective of external behavior.

Thus, the main difference between them is the level of access and knowledge about the internal implementation of the system, which influences the methods and strategies of testing.