解释Built-in commands

Built-in commands refer to commands that are built into the operating system's shell or command interpreter. These commands are usually executed directly by the shell or interpreter, without the need for an external executable file.

Examples of common built-in commands include cd (change directory), echo (print text to the console), pwd (print working directory), and history (display a list of recently executed commands).

Built-in commands are typically faster and more efficient than external commands because they do not need to be loaded into memory from disk. They are also often more versatile and customizable since they can be tailored to the specific needs of the operating system and the user's preferences.