I am new to computer systems and TAKING intro classes. I have a question regarding operating systems. Why not combine the kernel and the shell to make the OS just one thing? I figure there must be a reason why they are not together. Thank you for your time.Shell often means a program that makes human interaction with the kernel. It is not used doing normal running of programs that ink into the kernel. HOWEVER, scripting languages may use the shell. It is practical to have other shells.
If an improvement is needed for the shell, it is easy to make a new shell without doing the kernel over again.
Is that enough? There has been a debate about how much modularity there should be in modern computer systems. A modular system ALLOWS different people to make changes to specific parts of the system and still have it work. But standardization makes it difficult to explore new OFFBEAT methods to solve problems.

Maybe this article will help explain what I just said.
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Modular programming (also called "top-down design" and "stepwise refinement") is a software design technique that emphasizes separating the functionality of a program into independent, interchangeable modules, such that each contains everything necessary to execute only one aspect of the desired functionality.[1] Conceptually, modules represent a separation of concerns, and improve maintainability by enforcing logical boundaries between components. Modules are typically incorporated into the program through interfaces.[2] A