I read the book “Click Clack Moo, Cows That Type”,  by Doreen Cronin. Illustrated by Betsy Lewin .  The book tells the story of Farmer Brown’s cows, who find an old typewriter in the barn and proceed to write letters to Farmer Brown, listing various demands.  I then brought out a manual typewriter and explained that these were used to type letters before we had computers.  The children have had several classes to experiment with the typewriter!