An outmoded text editor that allowed text to be changed a line at a time. Ed was the original Unix line editor dating back to the early 1970s, and Edlin was the editor that came with DOS PCs in the early 1980s.
There was no vertical scrolling. The text in a file was edited one line at a time by referencing the line number. Instead of being able to edit a file by expanding and shortening all the text in the file as with all subsequent text editors, a line editor required only elementary programming skill to create. See text editor