In the Beginning was the Command Line
We sometimes forget the origins of modern computer systems. In the very early days, computers were room-sized behemoths, where operators would input data using switches. Computers finally become a tool for everyday use when you could "talk" to the system using a more typical process: typing commands. Sure, eventually we moved to graphical interfaces with a mouse or touchscreen, but in the beginning was the command line.
Neal Stephenson wrote about this in his 1999 book: In the Beginning was the Command Line. It's a great read. If you'd like to borrow the book, let me know, it's on my office bookshelf. But now Neal has released his book for free via the web, in plain text format, so you can load it into a variety of e-book readers.
About twenty years ago Jobs and Wozniak, the founders of Apple, came up with the very strange idea of selling information processing machines for use in the home. The business took off, and its founders made a lot of money and received the credit they deserved for being daring visionaries. But around the same time, Bill Gates and Paul Allen came up with an idea even stranger and more fantastical: selling computer operating systems. This was much weirder than the idea of Jobs and Wozniak. A computer at least had some sort of physical reality to it. It came in a box, you could open it up and plug it in and watch lights blink. An operating system had no tangible incarnation at all. It arrived on a disk, of course, but the disk was, in effect, nothing more than the box that the OS came in. The product itself was a very long string of ones and zeroes that, when properly installed and coddled, gave you the ability to manipulate other very long strings of ones and zeroes. Even those few who actually understood what a computer operating system was were apt to think of it as a fantastically arcane engineering prodigy, like a breeder reactor or a U-2 spy plane, and not something that could ever be (in the parlance of high-tech) "productized."
You can find the complete, downloadable book here: www.cryptonomicon.com/beginning.html