how the matrix of glOrtho is derived?

I am new to OpenGL but have 3D geometry background. I check the refernece of OpenGL function glOrtho at glOrtho | Microsoft Learn. The corresponding orthographic projection matrix of glOrtho is given. But I cannot figure out how the matrix is derived. Could someone explain this for me please? Thanks.

What do you mean by “how the matrix is derived”?

Hi, I mean in what steps the matrix is obtained.

Here is a reference:

Thanks, that’s what I am looking for.