I was explaining two’s complement recently1 to a friend, and I thought my explanation was decent, so I decided to write it up and share it with you, my general blog audience, as well! If you already know about two’s complement, this is pretty much just a review. If not, you may learn something, and you may not understand all of it. Try to get what you can without getting too anxious, there will not be a test!

In previous posts, we discussed historic operating systems and where various OS features come from, but we only gave a brief overview of how they worked. Now that we have a modern operating system’s full complement of features, we can look at what components need to exist in a modern operating system to get those features. As discussed with MS-DOS, an operating system, even today, is partially code, and partially conventions, like file formats or rules of good behavior – the difference being, that modern operating systems have more ability to enforce some of these conventions.

We use operating systems all the time in our life, whether designed for a computer, a phone, or for a server we’re more indirectly interacting with, but a lot of people don’t know very much about what connects the different systems we use, and what makes them distinct. We discussed fundamental concepts of operating systems in the last post, so in this post we will discuss how some of the same concepts apply to modern operating systems, going over them one at a time.

A user of modern technology hears the term “operating system” thrown around a lot. Most people can name a few examples: Windows and macOS on workstations and laptops, iOS and Android on phones. Some people might even throw in Linux or Unix or ChromeOS. Most people also understand that a program or a game or even a sufficiently advanced website might work on some operating systems but not others, and might require different versions for different operating systems.