[BlackDeath3]

If all you're looking to do is simple stuff (like get a rectangle on the screen), shaders are not required, correct?

[exDM69]

You do need shaders for pretty much everything.

But if you only want to draw a rectangle with a solid color, you can do that using the scissor test and clearing "the screen". But that's about all you can do without shaders.

[Narishma]

They are, unless you use old deprecated versions of OpenGL.

[BlackDeath3]

So the simplest program using the simplest shader would use a pass-through shader that doesn't modify the inputs?