the DOS shell concept

Conceptually speaking, just like the shell of a walnut the DOS programs command.com and cmd.com surround the operating system’s insides and provide the end user with something firm and easy to grasp. The shell is the interface that the user communicates with.Command.com and Cmd.exe are DOS programs located in the shell. The kernel is the machine language programs which is surrounded by the shell. The hardware (which would be useless without software) is the computer machine itself and is surrounded by the kernel. The languages and tools encapsulate the shell and is the outermost layer of the DOS analogy to a walnut.
In DOS, folders and subfolders are labeled directories and subdirectories. In DOS one can create these directories and subdirectories. If you type “Format” on the DOS screen and hit “Enter” it prepares a disk for use. If you type “Copy” and hit “Enter” it makes a copy of the file. If you type “CHKDSK” and hit “Enter” it checks the characteristics of the disk and system. DOS provides the software substructure and facilitates for the other programs that run on the computer and allows you to run programs, keep track of files on disk and handle input and output.