Question

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

Answer 1

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.