In the first half of the 20th century, scientists started using computers, mostly because scientists had a lot of math to figure out and wanted to spend more of their time thinking about science questions instead of spending hours adding numbers together. For example, if they had to launch a rocket ship, they needed to do a lot of math to make sure the rocket worked right. So they put together computers. These analog computers used analog circuits, which made them very hard to program. In the 1930s, they invented digital computers, and soon made them easier to program. However this is not the case as many consecutive attempts have been made to bring arithmetic logic to l3.Analog computers are mechanical or electronic devices which solve problems.Some are used to control machines as well.