For novice users, this section presents basic concepts about the UNIX shell. For advanced users, this section also summarizes the major similarities and differences between the Bourne, Korn, and C shells. Details on the three shells are provided in Sections 4 and 5. Common features Differing features 3.1 Introduction to the Shell Let's suppose that the UNIX operating system is a car. Through the car's drive mechanism, which can be thought of as the car's user interface.
Some systems provide only one shell.
Many provide more than one for you to choose from. Each shell has different features, but all of them affect how commands will be interpreted and provide tools to create your UNIX environment. The shell is simply a program that allows the system to understand your commands. In our car analogy, this is comparable to pressing the brake.