INVITATION TO CYBERSECURITY 24 Table 2.5 Hello, World! programs in different languages.4 2.3.3 The Operating System “UNIX is basically a simple operating system, but you have to be a genius to understand the simplicity.” - Dennis Ritchie, co-creator of UNIX All general purpose computers come with one very important piece of software that runs continuously called the operating system (OS). This computer program underlies all of the other computer programs that run on a computer. UNIX is one of the most influential OSs ever created. It was designed by Ken Thompson and Dennis Ritchie in the 1970s and became the model for many modern OSs. The three main OSs in use in computers today are Microsoft’s Windows, Apple’s macOS, and the free and open-source operating system Linux. These OSs are enormously complex and include tens of millions of lines of source code that took tens of thousands of man hours to produce. Some of the most well-known names in computing became famous because they are behind these OSs which together underpin most of the computers in the world. Bill Gates and Paul Allen co-founded Microsoft in 1975, Steve Jobs and Steve Wozniak co-founded Apple in 1976, and Linus Torvalds developed Linux which is based on UNIX and was first released in 1991 (its name comes from the combination of Linus and UNIX). Linux is elegant, reliable, and unlike Windows and macOS, it is free! Because it is open source, its source code can be vetted and modified to suit different purposes. Thousands of programmers have contributed to its development over the years, and have packaged 4 The source for the Hello, World! assembly language program is: talaatmagdyx.gitbook.io website. Displaying “Hello World!” in x86 Assembly. Retrieved June 2025.
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