What type of input did the command line interface allow?

The command line interface (CLI) primarily allows users to input written commands. This mode of interaction is different from graphical user interfaces (GUIs) which often utilize visual elements like buttons and icons for user interaction. In a CLI, users type text commands into a console or terminal, thus communicating directly with the computer's operating system or applications through text-based instructions. This method of input is particularly powerful for experienced users because it can allow access to a wide range of functions and operations quickly and efficiently, often with more flexibility than GUI alternatives.

Other forms of input, such as graphical commands, mouse clicks, or voice commands, do not align with the fundamental nature of a CLI. Graphical commands and mouse clicks are features of GUIs, where visual elements guide the user’s actions. Voice commands involve speech recognition technology that is typically not a part of traditional command line interfaces. Hence, the written command is the key characteristic that defines the interaction model of a command line interface.