Why did GLSL change varying to in/out?
<p>I know how to use both in/out variables, and varying variables. I am fully aware that using the in/out variables is better because it is not deprecated.</p>

<p>It is a very small thing, but I don't really understand why they changed this. Previously I could have the code in one shader, copy and paste it into the other, and it would be fine. Now I have to paste it into the other and change everything to "out" (instead of "in").</p>

<p>It is not that I mind doing this, I am just very curious about whether there is an advantage to the in/out variables, and if there isn't, why did the Khronos group change it.</p>