The history of the shell

I thought maybe you would like to know the history about shell and where it came from. I just realize that the term shell came from the fact that it hides all the operating system’s low-level calls so that it only show the input, output and error and hide all the details that happened in the OS. In the picture below you can view the history of the shell, thought you might like it though.

clipped from www.ibm.com