[MUSIC] Welcome back. We'll quickly go over a small set of conceptual preliminaries after which we will get into other software tools that will be used in this course. And these are fundamental questions again, conceptual preliminaries a fundamental question. Question one, what is efficiency? And the reason we want to know that, is because the answer to that question helps us answer this one. What is productivity? And why do I want to know what is productivity? Because that leads to the answer to this third question. What is technology? And once we are there then the fourth question comes about. How is technology different from science? Why should we care about that? Because that difference ultimately in some sense is going to play out here in the definition of platforms both for technology, and for businesses. So let's go to the first question, what is efficiency. Given any system there are some inputs and there is an output. Efficiency is basically the rate of output per unit input. That's basically what it is. What is productivity. Productivity is a particular type of efficiency. It is the average measure of the efficiency of production. Economic production, that's basically what it is. Productivity is an economic term, yeah? Which brings up the question, what is technology? Any set of means, any set of tools, any processes that can raise productivity is a technology. Examples, think of the printing press, right, which raised the productivity, the efficiency with which written text could be produced by orders of magnitude and so on. How is technology different from science? Well, basically pure science is the base, the application of that science to raise productivity is technology. It's basically the raising of productivity that makes something a technology. Innovations in some sense also fall under that definition. Which brings up the question, what are platforms? Platforms are basically exchanges or marketplaces. There is a platform owner who sets the rules and people who come there play according to those rules, that's basically what a platform is. People and businesses trade as per the rules set by the platform owner. Example, Android, it's a platform, there are rules and people basically come and exchange things there, trade. Your third part developers, your consumers, your apps, an entire ecosystem built around a platform. Another example eBay, a platform created where people could exchange value consistent with the rules set by the platform owner. Now that we have some idea basically of what we mean by platform and by technology, let us now jump into in some sense the software enablers of this course. But before that, a series of quick questions I'd like you to take. Think about in terms of what is a platform and what isn't. [MUSIC]