Choice of interface Most modern systems allow individual users to select their desired interface, and to customize its operation, as well as the ability to switch between different interfaces as needed System administrators generally determine which interface a user starts with when they first log in GUI interfaces usually provide an option for a terminal emulator window for entering command-line commands Command-line commands can also be entered into shell scripts which can then be run like any other programs- Choice of interface • Most modern systems allow individual users to select their desired interface, and to customize its operation, as well as the ability to switch between different interfaces as needed. System administrators generally determine which interface a user starts with when they first log in. • GUI interfaces usually provide an option for a terminal emulator window for entering command-line commands. • Command-line commands can also be entered into shell scripts , which can then be run like any other programs