What is the main difference between Windows API, DirectX and OpenGL?

Question

API

What is the main difference between these three interfaces? The fact that one of them, namely WinAPI , works at a high level by referring to the system itself, and the other ( DirectX ) at a low level by referring to the GPU ?
In the case of OpenGL , everything is clear - it works at a low level, as it is said in truthful sources. Is it the same with DirectX ? But why isn't it cross-platform then? After all, in the case of programming at a low level, everything depends on the hardware, and not on the OS, right?

Answer 1

The question should be:
"What is the main difference between GDI/GDI+ , DirectX and OpenGL?"
The Windows API is not only GDI and GDI +, but also a GUI, a network file system, in short, a full-fledged low-level (for the 21st century) OS API, on which all programs are written in one way or another. And it's clear from the name, isn't it?
GDI/GDI+ was originally designed not for games, but for GUI rendering, which in those good old days was not associated with such a bunch of whistles and fakes as it is now. That's why it's not designed for complex graphics, and the bells and whistles of GDI + is the ceiling of graphics capabilities for the GUI.
Well, at least because it is compiled into the dll format, which will not work on Linux, Mac, Android, iOS. On android, you also need a different architecture. And there are no sources - proprietary - so do not rebuild.
Disassembling is illegal + technically difficult and difficult, with me such work would result in a 6-7-8-digit amount (in rubles), and it would take months ...))) no make, or anything decent, and sell it instead of porting DirectX "to be".

Answer 2

DirectX is a proprietary solution from Microsoft that only works on windows. In addition to graphics, it also provides work with the network, input devices (including feedback) and sound.
OpenGL is a cross-platform solution that works only with graphics.
WinAPI (GDI) is a solution for writing application software, not designed to work with serious graphics and explicit use of an accelerator.