There are so many areas in Computer Science and the technologies that make up this vast sector can range from basic to outlandishly complex and difficult.
The web, for example, encapsulates just one area of the industry, yet in itself has an immeasurable amount of languages, frameworks, tools etc. I'm sure the typical web developer could rattle off 20-30 off the top of their head.
But, each and every concept/language/technology/tool required some form of learning to begin to us - whether basic or otherwise.
Tough learning curves can be occur for a number of reasons. Perhaps that language had poor or non-existent documentation; perhaps it was difficult to find support online or from peers for that tool; perhaps that technology required context from another technology to learn it effectively?
Whatever the reason and whatever the concept/language/technology tool, it is very interesting, and often surprising, to discover what people in the industry have found to be the steepest learning curves, and why this was the case.
And, perhaps by addressing and discussing some of the learning curves faced, we can begin to find solutions to the issues for future generations of developers.
So, what have been your biggest learning curves, and why?