Happy birthday to IBM's Selectric typewriter! The Selectric typewriter was a successful model line of electric typewriters introduced on July 31, 1961. Traditional typewriters have individual typebars that strike the ribbon and page. The Selectric typewriter, on the other hand, had a typeball with letters on it and rotated to the correct position before striking. The type element could be changed out to use different fonts on the same document. IBM's Selectric typewriter replaced the moving carriage of a traditional typewriter with a paper roller that stayed in position while the typeball and ribbon mechanism moved from side to side. The Selectric and its descendants eventually took 75% of the United States market for electric typewriters used in business. A replacement called the Wheelwriter was then introduced in 1984.