Typewriter and Adding Machine
A typewriter is a mechanical or electromechanical device with a set of "keys" that, when pressed, cause characters to be printed on a medium, usually paper. From their invention before 1870 through much of the 20th century, typewriters were indispensable tools for many professional writers and in business offices. By the end of the 1980s, word processor applications on personal computers had largely replaced the tasks previously accomplished with typewriters. Typewriters, however, remain popular in the developing world and among some niche markets, and for some office tasks.