History of Computers - The Difference Engines
Contents
Overview
Introduction
Charles Babbage, a British inventor and mathematician, was completely fed up with having to calculate everything by hand using mathematical tables. Human error was only too common an occurrence. Being the genius he was, he decided to solve that problem by building his own machine capable of compiling these mathematical tables. This machine would become known as the Difference Engine.
How the Engines Worked
The engines were mostly clunky calculators. They would perform calculations by a method of repeating addition according to the method of finite differences. This method worked by making a table of the differences between subsequent outputs for a polynomial of degree ‘’n’’ ‘’n’’ number of times.[1] They were considered decimal digital machines; Decimal because they used decimals 0-9 and digital because only whole numbers were valid. Numbers took the form of gear wheels and each digit of a number had a separate wheel. The Engines were actually programmed with their own form of error detection in that they jammed if a value landed in between whole numbers, indicating that the calculation imputed was in a sense corrupted and had to be re done.
The Difference Engines - Engine No. 1
In 1821, Babbage designed Difference Engine No. 1 to calculate and tabulate polynomial functions. It would calculate numbers and print them automatically on a table. Babbage wanted the engine to be automatic in that if it was supplied with numbers it would be able to calculate and output solutions without human intervention.[1]In 1822 he completed a prototype of the engine and received a grant from the British Government for £1500.[1]In 1833, with the assistance of Joseph Clement (A tool maker and draftsman), a 7th of Difference Engine No. 1 (consisting of ~2,000 parts and nicknamed the beautiful fragment by Babbage) was completed.[3] This fragment is the only part of Difference Engine No. 1 ever completed, for Babbage and Clement had a major dispute and Clement quit with only half the parts made.[3] Thus Difference Engine No. 1 was never completed, but fully designed.
Difference Engine No. 2
After completing the Analytical Engine, Babbage had new ideas on how to improve the design of his previous Difference Engine. Between the years 1847 and 1849 Babbage designed a new Difference Engine that he called Difference Engine No. 2. This improved engine could calculate with numbers 31 digits in length and could tabulate polynomials up to the 7th order, or an n of 7.[5] Difference Engine No. 2 shared the same design for a printer as the Analytical Engine.The efficiency of this new engine was also massively increased, as it only required one third of the parts that Difference Engine No. 1 required for greater computing power.[6] Babbage sadly failed to build this machine in his lifetime, but in 1985 the Science Museum in London decided to start a project to construct Difference Engine No. 2 according to Babbage's plans.[7] 17 years later, the Engine was complete, weighing 5 tons and measuring 7 feet high, 11 feet long, and 18 inches deep at its narrowest.[7] A video of the working engine can be found here.[8]
Significance
The Difference Engines, though only oversized calculators, were capable of working with complex equations and variables in ways that could be only dreamed of at the time. Babbage stoked the idea of mechanical calculation and inspired future inventors to go further with his ideas. More importantly, Difference Engine No. 1 was the precursor to the Analytical Engine, which is widely considered the first computer created and was originally just an expanded Difference Engine. Without these Engines, a computer would have probably still been created, but at a much later time and in a very different manner. In fact, the computers we use today would have probably evolved much differently and be very divergent from the machines we know so well today.
References
- ↑ 1.0 1.1 1.2 [https://books.google.com/books?id=tXBVAgAAQBAJ&pg=PT22&dq=difference+engine+1819&hl=en&sa=X&ved=0ahUKEwi-jbWJ4rrdAhVGmK0KHf7qA1UQ6AEISzAG#v=onepage&q=difference%20engine%201819&f=false
- ↑
- ↑ 3.0 3.1 [1]
- ↑
- ↑ [2]
- ↑ [3]
- ↑ 7.0 7.1 [4]
- ↑ https://www.youtube.com/watch?v=be1EM3gQkAY
