Shell is a special feature. ProgramIt is an interface between the user and the core program (kernel) of the UNIX and Linux operating systems;
Various operating systems have their own shells. For example, the shell of DOS is the command.com file, such as ndos, 4dos, and drdos under DOS... in UNIX, except for bourneshell, C shell, KoRn shell, Bourne again shell, tenex cshell, and other shells. when the system starts, the core program is loaded with memory to manage the system until the system is shut down. It establishes and controls the processing program, manages memory, and manages files, communication and so on. Other programs, including Shell programs, are stored in the disk. The core program loads them into the memory, executes them, and clears the system after they are aborted; shell is a public program. It is started when you move in, by interpreting the commands entered by the user (by command or command file); shell provides the user and program to generate the conversation function;
