For centuries, teams of people were frequently employed to undertake long and tedious calculations, often working in Parallel computing. From the early 17th century to the middle of the 20th century they were called computers. Now the word refers to device that can be programmed to carry out a set of arithmetic or logical operations automatically. By designing it so that the sequence of operations can be readily changed, the computer can solve more than one kind of problem. Other ancestors to the modern computer can be seen in this gallery.