Some History

Before closing this introduction, let us present a brief history of how operating systems developed. Like any system built by humans, good ideas accumulated in operating systems over time, as engineers learned what was important in their design. Here, we discuss a few major developments. For a richer treatment, see Brinch Hansen’s excellent history of operating systems“The Evolution of Operating Systems” by P. Brinch Hansen. In ’Classic Operating Systems: From Batch Processing to Distributed Systems.’ Springer-Verlag, New York, 2000. This essay provides an intro to a wonderful collection of papers about historically significant systems..

Early operating systems: just libraries

In the beginning, the operating system didn’t do too much. Basically, it was just a set of libraries of commonly-used functions; for example, instead of having each programmer of the system write low-level I/O handling code, the “OS” would provide such APIs, and thus make life easier for the developer.

Usually, on these old mainframe systems, one program ran at a time, as controlled by a human operator. Much of what you think a modern OS would do (e.g., deciding what order to run jobs in) was performed by this operator. If you were a smart developer, you would be nice to this operator, so that they might move your job to the front of the queue.

This mode of computing was known as batch processing, as a number of jobs were set up and then run in a “batch” by the operator. Computers, as of that point, were not used in an interactive manner, because of cost: it was simply too expensive to let a user sit in front of the computer and use it, as most of the time it would just sit idle then, costing the facility hundreds of thousands of dollars per hour“The Evolution of Operating Systems” by P. Brinch Hansen. In ’Classic Operating Systems: From Batch Processing to Distributed Systems.’ Springer-Verlag, New York, 2000. This essay provides an intro to a wonderful collection of papers about historically significant systems..

Beyond libraries: protection

In moving beyond being a simple library of commonly-used services, operating systems took on a more central role in managing machines. One important aspect of this was the realization that code run on behalf of the OS was special; it had control of devices and thus should be treated differently than normal application code. Why is this? Well, imagine if you allowed any application to read from anywhere on the disk; the notion of privacy goes out the window, as any program could read any file. Thus, implementing a file system (to manage your files) as a library makes little sense. Instead, something else was needed.

Thus, the idea of a system call was invented, pioneered ...