What are the different layers of Unix architecture?
Hardware: This refers to the hardware layer of any computer system
Kernel: This sits on top of Hardware and it interacts with the hardware. This is the core of the Operating system and acts as an interface between the user activities and the hardware. It provides the base functionality of the OS. The major functionality of the kernel includes process management, memory management, thread management, scheduling, I/O management and power management.
Shell: This is an interface between the user and the kernel. It interprets the commands from a user and executes the resulting request. Post processing the commands kernel returns back the instructions to the shell.
There are various types of command line shells in Unix: Bourne Shell, C Shell, Korn Shell, Bourne Again Shell (bash).
User: communicates with Shell through Commands.
That’s good to understand all about the architecture.
But how does Shell works?
As mentioned earlier the user communicates with Shell through Commands. Shell being a command interpreter translates them into the kernel understandable language. Kernel then processes the results and sends back if any response is available to the shell. The shell finally displays a prompt back to the user.
Please find below the features of the Shell. In our next series on Unix we will explore I/O redirection and Pipes. Hope our readers have enjoyed this short and crisp article.
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Features of Shell:
Shell interprets the valid user entered commands to the kernel understandable language. Shell should understand which program to be invoked in order to perform thatcommand.
Ideally prompts are shown as “$” or “#”
Uses multiple shell commands logically to create a script i.e. runs more than one commands at a time.
I/O redirection and Pipes
These features in Shell allow connecting programs together and making programs process their inputs from files.