C SC 100 Lecture Notes
Autumn 2009
Pete Sanderson

The Machine That Changed The World

PBS Video Series
A production of WGBH and the BBC


Topic Summaries & Notes
© 1997-8 by David J. Stucki


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(Thanks to John A. N. (JAN) Lee for providing links to many of the resources listed below.)

Giant Brains, Episode 1

Introduction

Writing was invented 5000 years ago as a means of expanding our ability to communicate. The computer may come to rival the written word as a communication medium. 

Most machines are special purpose, that is they are designed to do only one thing. Computers, on the other hand, are universal machines. They can transform themselves into a variety of other machines through the use of software. As a result the computer is a uniquely versatile machine. 

This universal character of computers allows us to describe their functioning as:  In general, computers perform tasks that in humans requires intelligence to accomplish. Originally, computers were invented to provide a fast and effective means of performing arithmetic.  

The Human Computer

Prior to World War II the word computer referred to a person who computed arithmetic tables, such as for logarithms or numerical constants. For example, William Shanks spent 28 years of his life calculating the value of p, the ratio of the circumference of a circle to its diameter,  to 707 decimal places. A modern desktop computer can solve the same task in 7 seconds or less. 

The human computer relied primarily on tables (prepared by other computers) and often made calculation errors, transcription errors, or propagated errors located in the tables. For example, Shanks made an error in the 528th decimal place and so the last few years of his efforts were wasted. 

The industrial revolution was built on numbers. As technology grew it created an increasing demand for accurate and reliable mathematical tables. 

Charles Babbage was a victorian mathematician who became frustrated by the amount of wasted time caused by computer errors. He independently commissioned two sets of tables in one instance to allow them to be checked against one another for accuracy. (See also The Babbage Pages, and the History of Mathematics archive.)  

The Difference Engine

Babbage conceived of an idea of an engine that would compute by steam or some other means of automation. He designed a machine he called a difference engine, so named because it computed using a technique called the method of differences. Because of the practical usefulness of this machine, the British government granted Babbage the financing he needed to build it. The machine, however, was never completed, partially because he was a poor manager and partially because he came up with a better idea. 

The difference engine only could compute results by the single method of differences, and was not, therefore, very versatile. Babbage envisioned an alternative, general purpose machine that would be programmable. He named this device the analytical engine. As a means of encoding the programs, Babbage borrowed the idea of using a series of punched cards from Jacquard, a french textile maker, who had used them to create looms that could weave complex patterns. 

This was the first machine that had been designed not with a specific purpose or function in mind, rather that was left to the user to specify. The concept of software was born. 

The First Programmer

Augusta Ada Byron, Countess of Lovelace, was the poet Lord Byron's daughter. She became fascinated with Babbage's analytical engine and is largely regarded as the world's first computer programmer (although there are some who disagree). She formed a long term association with Babbage after translating a paper written about his work. She spent a considerable amount of time working on the implications of a programmable machine and what it might be capable of. 

A New Era Dawns

During the decade between 1935 and 1945 the definition of the word changed dramatically. A common dictionary from before this period identified a computer as a person who performed calculations. By the end of World War II the word computer referred to a machine that was used for the same purpose. 

Konrad Zuse

Konrad Zuse picked up where Babbage left off, implementing several improvements and innovations along the way. His computer was the first electromagnetic computer, whereas Babbage's had been purely mechanical. He also pioneered the idea of using electric relays (common in telephone systems) as simple components, using binary arithmetic simplify the engineering. This was a considerable improvement over Babbage's decimal machines. By 1939 Zuse was the world's leading computer designer. To conserve resources and money during the war, he used discarded movie film instead of punched cards. 

He also conceived of the idea of building a completely electronic computer out of vacuum tubes, but was denied funding by the German High Command because they thought they would be able to win the war before he could finish building it. The idea of the vacuum tube machine, however, was a breakthrough since it could have speeds up to 1000-2000 times as fast as the mechanical relay machines. 

ENIAC and its Peers

The U.S. government was highly motivated during the war to develop digital, electronic computers to help them calculate artillery guidance trajectories. They had been utilizing the skill of human computers, such as Kay Mauchly from the University of Pennsylvania, who was employed building firing tables. Manually, it took about 4 years for one human computer to complete a single set of tables. 

John Mauchly and J. Presper Eckert, who were at the University of Pennsylvania's Moore School of Electrical Engineering (founded by Benjamin Franklin), developed a plan to build an electronic digital computer using vacuum tube technology. Their design called for 18,000 tubes (which had a failure rate of one every five seconds), which filled a room 50'x30'. The ENIAC (Electronic Numerical Integrator and Calculator), in addition to its complexity, incorporated several innovations. It was built according to a modular design that allowed it to have built-in fault tolerance (redundancies and backups to prevent overall system failure). The ENIAC was a technological triumph, but it was too late for the war effort. 

Kay Mauchley became an ENIAC programmer, which involved learning all the circuit diagrams for the machine, since reprogramming it involved rewiring all its circuitry. There were no user manuals in those days. Because of the work involved in reprogramming the ENIAC it spent much of its time sitting idle. 

America's most distinguished mathematician, John von Neumann, joined the ENIAC project towards it end and authored the report describing a new kind of machine that could store its programs in memory, rather than in the physical configuration of the machine. This stored program computer became the model for every modern computer designed and built since. 

Due to contractual and patents disagreements, Eckert and Mauchly left the University of Pennsylvania to start the first commercial computer company,where they developed the UNIVAC  

In July, 1948, Freddie Williams designed and built the Mark 1, the first working stored program machine at the University of Manchester. 

Maurice Wilkes, designed and built the Edsac computer (Electronic Delay Storage Automatic Calculator) with the idea of presenting a more user friendly interface that would attract the interest of scientists who may not have been competent electrical engineers. 

Predicting the Future

The invention of the computer ushered in the birth of entirely new disciples of science and research. For example, the field of radio-astronomy could not exist without its incredible speed and computational power. 

In 1950, most scientists might have been able to envision the continued innovations and technological breakthroughs that led to the development of the supercomputer, but few of them would have been able to predict the way in which personal computers have become a commodity. In fact, the popularity of the personal computer is very much a surprise given the ways in which the early computers were utilized. 

There were those, however, who suspected that computers were far more significant a technology than simply a fast means of automatic calculation. 

Alan Turing

Alan Turing was a British mathematician who was instrumental in the British military's code-breaking efforts in World War II. He is also recognized by many as the founder of computer science. With the publication of two important papers, one on the limits of computation (what computers can and cannot do) published in 1936 and the other somewhat related paper on whether machines can be built that are capable of thought, published in 1950, he laid the theoretical groundwork for much of the work done in computational theory and artificial intelligence. 

Turing recognized that there is nothing special about arithmetic that allows it to be automated as opposed to logic, code-breaking, or any other task that can be described symbolically in a formal system. He was associated with the Colossus project where he worked at Bletchley Park, the heart of the British code-breaking effort, which helped to win the war. 

Turing's main interest, though, was in designing a computer for non-numerical calculations. He designed a machine called the Automatic Computing Engine (ACE) in 1945 which he intended to use for symbolic computations, but a working model wasn't constructed until 1950. 

In a lecture at his alma mater, Turing described computation as anything that can be described in symbols, and compared the behavior of machines manipulating numbers as not any different from those manipulating characters. He suggested that computers are able to learn by experience, and that as a result they don't really do only what they're told to do. He also explained a kind of game (now called the Turing Test) that would allow a computer to convince a person that it was intelligent.


Comments, feedback, or inquiries, please contact DStucki@otterbein.edu

Last updated:
Pete Sanderson (PSanderson@otterbein.edu)