A shell is a program that acts as an interface between the user and the operating system. A shell allows the user to interact with the operating system by accepting commands entered by the user from the keyboard, verifying if the inputs from the user are correct, and executing them. Generally, a shell is a user interface that allows us to use computer resources such as memory. It can take two forms:

1. Command-line interface, such as Bash.
2. Graphical user interface, such as Windows Office.

##Implementation The program first estabilishes whether it is working in interactive or non-interactive mode and based on that runs as follows: ###Interactive mode

###Non-interactive mode