How Did They Get to the Moon Without Powerpoint?

How Did They Get to the Moon Without PowerPoint?

Mordechai (Moti) Ben-Ari Department of Science Teaching Weizmann Institute of Science [email protected]

Keynote speech at the Finnish Computer Science Society, May, 2003.

1 Developing a Technology The invention of writing, however, was the invention of an entirely new Let me start with a description of one of my first technology.[3, p. 9] full-time jobs: There is something to be said for this definition: I developed a technology for data min- do you remember those old movies that show “typ- ing in order to consolidate enterprise- ing pools,” where rows and rows of people, usually customer relations. women, sat pecking away at keyboards all day? Since I held that job in the early 1970s, clearly I would not have described my work in this terminol- ogy! What I actually did was: I wrote a program that read the system log, computed usage of CPU time and printed reports so that the users could be billed. My point in this talk is that hi-tech in general and computer science in particular did not begin in the 1990s, but that we have been doing it for decades. I believe that today’s students are being fed a lot of marketing propaganda to the contrary, and that they Well, things haven’t changed all that much! have completely lost a historical perspective of our discipline. I further believe that we have a respon- sibility as educators to downgrade the hype and to give our students a firm background in the scientific and engineering principles of computer science. The idea for this talk came to me while reading the hi-tech supplement that appears occasionally in a local newspaper. The supplement has a section in which they profile new startup companies, and invariably these companies “develop a technology,” though as far as I can understand from the short pro- files, they have simply designed and constructed a box of electronics or a computer program. So what is a “technology”? Here is one extreme view: I wouldn’t go so far as to claim that microchips Basically, microchips are merely a tech- are a mere “technical improvement,” but I certainly nical improvement over clay tablets. can’t accept that every new gadget or program is a

1 new technology. Here is a list of a few inventions 1974 - Vint Cerf and Bob Kahn published • that I would classify as new technologies: fiber op- “A Protocol for Packet Network Interconnec- tics, flash memory, celluar communication, public- tion,” which specified in detail the design of a key cryptography, functional and logic program- Transmission Control Program (TCP). ming, packet protocols, fault-tolerant algorithms. What is common to all these “technologies” is that The relatively recent invention of web browsers is they brought about a radical new way of solving thus mere syntactic sugar on a very mature technol- problems, and that they stimulated research and de- ogy. velopment that continued for many years. To be fair, there is some justification for looking upon the Internet as a new technology. In 1993-4, I attempted to write a program (excuse me, develop a 2 The Internet Revolution? technology) and found a startup company to market it. In order to obtain a connection to the Internet, If there is one system that epitomizes the new hi- I was required to receive permission from the Min- tech world, it is the Internet. It enables us to engage istry of Communications, because at that time the in shopping, exchanging messages and sex, which only connections were through an inter-university are things we couldn’t do before. Ask your students hub and so I had to prove that I was engaged in when the Internet was invented and I wouldn’t be R&D! Of course, this merely shows that the obsta- surprised if their guesses averaged about 1990. It cles to the spread of the Internet were political and is therefore highly instructive to actually look at a economical, not technological. timeline of the milestones of its development. I’ll There are many visionaries who have held out only list a few of the major early milestones and re- extravagent promises for our wired future, not the fer you to [10] for more detail. least, ex-vice president of the US Al Gore with his information superhighway. Here is an example of 1961 - First paper on packet switching by such a utopian vision from Michael Dertouzos of • Leonard Kleinrock. MIT: A common bond reached through elec- 1968 - Bolt Beranek and Newman, Inc. • tronic proximity may help stave off fu- (BBN) was awarded the Packet Switch con- ture flareups of ethnic hatred and na- tract to build Interface Message Processors tional breakups. (IMPs). 1 Here are some additional quotes. Do you know 1969 - ARPANET was commissioned by DoD • when they were written? for research into networking. The first pack- ets were sent by Charley Kline at UCLA as he It is impossible that old prejudices and tried logging into SRI; the system crashed as hostilities should longer exist, while the letter G of LOGIN was entered. such an instrument has been created for the exchange of thought between all the 1971 - Ray Tomlinson of BBN invented an nations of the earth. • email program to send messages across a dis- [It] may not affect maganzine literature, tributed network. but the mere newspapers must submit to destiny, and go out of existence. 1973 - Bob Metcalfe’s Harvard PhD Thesis • outlined the basic idea for Ethernet. The con- The merchant goes home after a day of cept was tested on Xerox PARC’s Alto com- hard work and excitement to a late din- puters, and the first Ethernet network was ner, trying amid the family circle to for- called the Alto Aloha System. get business, when he is interrupted by a [message] from London, ..., and the 1973 - The File Transfer specification and poor man must dispatch his dinner as • Network Voice Protocol specification were hurriedly as possible in order to send off published. his message to California. The business 1US Senator Edward Kennedy congratulated BBN on ecumenical Interfaith Message Processor, which shows that you can’t trust politicians to understand technology.

2 man of the present day must be contin- April 1973. He placed this call to Joel Engel, Head ually on the jump[.] of Research at Bell Labs, which was also trying to develop the technology. Clearly, it takes some time These are clearly utopian visions that high- for new technologies to mature and to be widely ac- technology will bring us peace, brotherhood and cepted, but while celluar communication is certainly the paperless office, though instant communication a new technology, it does not follow that if you add throughout time zones will cause extreme stress in a camera to a cell phone, then you have developed a the work environment. new technology. This is just normal development of And here is a characterization of the monopolis- a mature technology and we will have to wait to see tic practices of the leading company: if it will be successful in the marketplace or not. Not surprisingly, the company regarded I want to make it clear that I am not a Luddite. its near monopoly as a good thing. The Luddites were English workers who protested Far from encouraging progress [the the changes of the Industrial Revolution, destroying CEO] claimed, competition between ri- wool and cotton mills early 19th century. The British val companies had actively hindered government suppressed the riots, executing 17 men it. . . . [The company] insisted that its in 1813. Since then, the term Luddite has come to monopoly was in everyone’s interested, denote one who opposes advances in technology. even if it was unpopular, because it would encourage standardization. Is the author talking about Bill Gates and Microsoft? In fact, the quotes are taken from mid-19th century commentary on the use of the telegraph, and the monopolist CEO was William Orton of Western Union. Here is how Thomas Standage characterizes the introduction of the telegraph [8, p. vii-viii]: A new communications technology allowed people to communicate almost instantly across great distances. It rev- olutionized business practice, gave rise to new forms of crime, and inundated its users with a deluge of information. Ro- mances blossomed, secret codes were devised and cracked. The benefits of the network were relentlessly hyped by its advocates and dismissed by the skep- tics. Governments and regulators tried and failed to control the new medium. A technological subculture with its own customs and vocabulary was establish- ing itself. If I may be allow to quote from the Bible: Mita¨ on I make my living from computers and always ollut, sita¨ on tulevinakin aikoina, mita¨ on tapahtunut, have done so. I routinely use the Internet and can’t sita¨ tapahtuu edelleen: ei ole mitaän¨ uutta auringon bear to be away from my email for more than a day alla [Saarnaajan kirja 1(9)].2 In passing, it is worth- or so at a time. Furthermore, I have the all the mod- while noting that celluar communication is not at all ern gadgets: a cell phone, a Palm Pilot and a lap- a new technology. The concept was first proposed at top computer. I’m not a Luddite. But I believe that Bell Labs in 1947, and the first portable cell phone I have the perspective to see these gadgets as mere call was made by Martin Cooper of Motorola on 3 tools and not as a road to utopia. 2For non-Finnish speakers: The thing that hath been, it is that which shall be; and that which is done is that which shall be done: and there is no new thing under the sun. [Ecclesiastes 1:9]

3 3 Computer Science Social and Professional Issues • Unfortunately, I believe that we have also lost perspective in computer science. Each new system is Software Engineering • trumpted as a new technology, even though it may just be repacking of well-known technology. Let me Computational Science and Numerical Meth- give as an example the Java programming language • and system. First, let me say that while Java is not ods one of my favorite languages, I believe that it is quite well-designed and I use it extensively in teaching When I look at the detailed list of topics in and for developing software tools. But I cannot join net-centric computing, human-computer interaction, in the hype of Java as something new; it is simply graphics and visual computing, intelligent systems, an excellent packing of technologies that have been information management and software engineering, with us for decades, among them: I do find in each field a couple of topics with signifi- Compilation to a virtual machine - Pascal-P cant scientific content, but most topics are concerned • (1974). with specific applications and artifacts that are likely to become outdated. I know that students consider Object-oriented programming - Simula these to “new technology,” but I would much pre- • (1964). fer that they be taught more basic computer science and mathematics, as well as the basic concepts of Concurrency within the language - Concurrent • other fields such as electronics or economics. I am Pascal (1974). reminded of a project leader at an aerospace com- Library within the language - Smalltalk pany who once told me that in his experience, it is • (1969). easier to teach computing to a physics major than it is to teach physics to a computer science major. Even the cryptic syntax is taken from C which was developed in 1971. As far as I know, the only major innovation in Java is its built-in support for security. If we take a look at the new ACM/IEEE cur- riculum proposal, we can see an increased emphasis 4 How Did They Get to the on artifacts and specific applications. The proposal Moon? divides the “computer science body of knowledge” into the following 14 fields [1]: I promised to talk about the moon and it is time that Discrete Structures I fulfill the promise. Here is a quote from NASA’s • web site:3 Programming Fundamentals • Algorithms and Complexity • On July 20, 1969, the human race ac- complished its single greatest techno- Architecture and Organization • logical achievement of all time when a Operating Systems human first set foot on another celestial • body. Six hours after landing at 4:17 Net-Centric Computing • p.m. Eastern Daylight Time (with less than 30 seconds of fuel remaining), Neil Programming Languages • A. Armstrong took the “Small Step” Human-Computer Interaction into our greater future when he stepped • off the Lunar Module, named “Eagle,” Graphics and Visual Computing • onto the surface of the Moon, from Intelligent Systems which he could look up and see Earth in • the heavens as no one had done before Information Management him. • 3http://history.nasa.gov/ap11ann/introduction.htm.

4 Even if the style is a bit florid, I quite agree that this responding to them. NASA engineers recog- was the “single greatest technological achievement.” nized to source of the problem and allowed the You need only consider what it must have been like landing to continue [9]. to sit atop massive rockets and to entrust yourself to the intricate calculation of the celestial mechan- The first flight of the Space Shuttle was can- ics involved in performing the various rendezvous. • celed because of a synchronization problem The fact that six out of seven attempts to land on between the primary computer system and the the moon were totally successful is nothing short of backup computer system. It turned out to amazing. have been caused by an inconsistency between So what did the Apollo computer system look two scheduling algorithms that surfaced when like [9]. The Apollo Guidance Computer was “fairly modifications to software invalidated an as- compact” and weighed only 32 kilograms! sumption that a certain process would be ex- ecuted first. If the computer was turned on during a 15 ms window within each second, the problem would occur. The solution was simply to turn the computer off and on again [7].

During the Mars Pathfinder Mission, frequent • resets caused loss of data. The problem was diagnosised as priority inversion that caused a high-priority data management process not The execution of an instruction required two ma- to complete on time. The software was reini- chine cycles—about 24 milliseconds or 83kHz, and tialized to use priority inheritance [6], and the the computer had 36KB words of fixed memory and problem was solved [4]. 2KB words of erasable memory. Just for compari- son: I insisted that my boss buy me a modern Pen- The most expensive bug in history was prob- tium 4 computer with 256 megabytes of memory; • otherwise, it would have been impossible to run cer- ably the one that caused the French Ariane 5 tain modern Java-based pedagogical software. The rocket to explode on its maiden flight. The fixed memory (core rope) was unchangeable once it rocket’s computer system had reused software left the factory, so the software had to be delivered from the Ariane 4, but assumptions that had months before a mission for manufacturing and elec- been valid no longer held [5, 2]. trical testing, placing a premium on the production of quality software without hacking. And yet with These case studies are pedagogically extremely this computer system, NASA carried out the “single valuable, not only for their technical content, but greatest technological achievement of all time!” also because you can discuss issues of testing and I believe that instead investing so much ef- reliability that are often glossed over when desktop fort in teaching new hi-tech artifacts and in having software is developed. our students write large programs with fancy user- interfaces and web sites, we should be emphasiz- ing basics. The history of computing in space of- fers many interesting case studies that can be used 5 So How Can You Get to the to teach computer science. Moon Without Powerpoint? During the first landing on the moon, three • restarts during a 40-second period caused The presentation for the talk was written in LATEX 2ε warning lights to appear. The software using the Prosper style file. The LATEX 2ε source had given priority to interrupts that imple- files were typeset by the VisualTeX (a commeri- mented counter increment requests, and the cal system) into pdf. The pdf files compressed by rendezvous radar caused so many interrupts WinZip and displayed by Acrobat Reader. All the that 15% of the system resources were tied up files are, of course, portable.

5 References time synchronization. IEEE Transactions on Computers, 39:1175–1185, 1990. [1] ACM/IEEE-CS. Computing curricula 2001: Computer science volume. http://www.acm. [7] Alfred Spector and David Gifford. The Space org/sigcse/cc2001, 2001. Shuttle primary computer system. Communi- [2] Mordechai Ben-Ari. The bug that destroyed a cations ACM, 27(9):874–900, 1984. rocket. Journal of Computer Science Educa- tion, 13(2):15–16, 1999. [8] Thomas Standage. The Victorian Internet: The Remarkable Story of the Telegraph and [3] Florian Coulmas. The Writing Systems of the the Nineteenth Century’s On-line Pioneers. World. Basil Blackwell, Oxford, UK, 1989. Walker Publishing Company, New York, 1998. [4] Mike Jones. What really happened on Mars Rover Pathfinder. The Risks Digest, [9] James E. Tomayko. Computers in 19(49), 1997. http://catless.ncl.ac. spaceflight: The NASA experience. uk/Risks/19.49.html. http://www.hq.nasa.gov/office/pao/ History/computers/Compspace.html, [5] J. L. Lions. Ariane 5 flight 501 failure: Report 1988. by the inquiry board. http://ravel.esrin. esa.it/docs/esa-x-1819eng.pdf, 1996. [10] Robert H Zakon. Hobbes’ Internet time- [6] L. Sha, R. Rajkumar, and J. P. Lehoczky. Prior- line. http://www.zakon.org/robert/ ity inheritance protocols: An approach to real- internet/timeline, 2002.