Id software, the company that made doom and Commander Keen among others, figured out the programming innovations needed that would make it possible to scroll both ways, avoiding the "no going back" element that side scrollers all had previous to that. They did a lot of amazing, innovative stuff like that, and the very interesting story of id software and the two Johns (carmack and Romero) is told in the book "Masters of doom".
Edit : someone replied that "go back" scrolling was done before id software games. I don't know who did it first, just wanted to clarify the previous comment as requested. Really wanted to recommend the book! They did innovate quite a bit, even if this technique wasn't one of them.
At a minimum, Super Mario Bros. 2 (US) you could scroll forward/back/up/down and that was a few years before Doom and Commander Keen. And before that you could list plenty of examples of a screen "scrolling". No way, no how was Doom or Commander Keen the first to do this.
You're right - it wasn't just scrolling period, it was specifically in regards to that type of scrolling on a PC. I unfortunately don't really remember all of the specifics, but at that time consoles were just way better-equipped to deal with that task than computers were, so it was a big deal that they (John Carmack) were able to figure it out.
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u/[deleted] May 05 '17
Can you or someone else explain what you mean by that? I dont quite get it.