You called an "interrupt," which was basically a system call. That changed a bunch of timing registers within the video hardware. For a long time you basically could only do 40, 80 columns of text and 25, 43, or 50 lines. With some trickery you could get the video hardware to output 90 columns and with even more trickery you could get 60 rows.

If you made a custom font you could also have more diversity in the number of rows too but this was rarely done.

Eventually different text modes became available with higher resolution video cards and monitors. 132 columns of text were common but there were others.