When I was in highschool and university, I had to type essays, exams, and assignments on a typewriter. Although I was and am a fast and good typist, I could not proof read my work. If the ribbon ran out, I wouldn't know it. A story for another blog post. People had to proof read for me. since the advent of computers, I am now able to type and proof read for myself. I am able to save documents so that even if my printer runs out of ink, I can print a document somewhere else.