Before guis became popular, the interface was the most commonly used.

Before GUIs became popular, the command line interface (CLI) was the most commonly used.
GUI stands for Graphical User Interface . Like its name says it is a graphical interface that allows interaction with users through graphical icons and visual indicators , rather than through text-based interface.
Command line interace (CLI) is text-based interface in which the user issues commands to the program in the form of successive lines of text.