Comparison of Operating System Complexity Dan•Simon Myrland
[email protected] ABSTRACT It is plainly obvious that computer operating systems are growing increasingly complex every year, and have been for some time now. In the early days of UNIX a PDP11 with ¼ Mb of ram and 30 Mb of diskspace served its 100 users well, whereas today a computer with 10,000 times more resources is not even adequate for a single user. The increased complexity does not only tax our hardware but also our minds. Whereas Dennis Ritchie and Ken Thompson at Bell•Labs wrote the entire UNIX operating system and userland in a matter of weeks in the late 60’s, you would be hard pressed to find a developer today that can finish a company webpage within a year. Naturally you can do a lot more with a computer today then you could in the 70’s, but at what cost? This article does not give a definitive answer to the correct balance between providing the necessary features and keeping things simple, instead it simply analyses the complexity of operating systems, and their various components. Such analysis is illuminating in itself and can provide hints to the above question. Although commented, proprietary systems are not studied in detail here since it would be illegal to do so. Finally, only UNIX•like operating systems are analyzed. In practice very few viable non•UNIX exist, and comparing the handful that do with UNIX•like systems, would be comparing apples and oranges. Table of Contents CHAPTERS 1. Preliminary information 1 2.