What is Shell?

Shell

Shell provides an interface for the user to gain access to the kernel’s services. On Unix-based or Linux-based operating system’s, there is a shell command line interface (CLI) which allow the user to direct operation through computer commands, text, script.

                                                                                                                 

Shells created for other OS offer equivalents Unix shell functionality.

Shell is created through the implementation of the system startup script in Unix-based Operating System.

but in Windows, according to system's requirement shell scripts are preconfigured and run automatically. 

Unix Shell has the following categories-

• Bourne shell(sh) - This shell is given by Stephen Bourne at Bell Labs. Program name of Bourne shell is sh and its path in Unix is /bin/sh.
• C-shell - it is based on c programming language and written by Bill joy graduated from the University of California.
• Nontraditional shell -  
• Historical shell -
• Bourne again shell(Bash) - It is basically command processor which runs in a text window and execute a command that causes action.