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An Illustrated History of ComputersPart 1

John Kopplin 2002

The first computers were people! That is, electronic computers (and the earlier mechanicalcomputers) were given this name because they performed the work that had previously beenassigned to people. "Computer" was originally a job title: it was used to describe those humanbeings (predominantly women) whose job it was to perform the repetitive calculations requiredto compute such things as navigational tables, tide charts, and planetary positions forastronomical almanacs. Imagine you had a job where hour after hour, day after day, you were todo nothing but compute multiplications. Boredom would quickly set in, leading to carelessness,leading to mistakes. And even on your best days you wouldn't be producing answers very fast.Therefore, inventors have been searching for hundreds of years for a way to mechanize (that is,find a mechanism that can perform) this task.

This picture shows what were known as "counting tables" [photo courtesy IBM]

A typical computer operation back when computers were people.

The abacus was an early aid for mathematical computations. Its only value is that it aids thememory of the human performing the calculation. A skilled abacus operator can work onaddition and subtraction problems at the speed of a person equipped with a hand calculator(multiplication and division are slower). The abacus is often wrongly attributed to China. In fact,the oldest surviving abacus was used in 300 B.C. by the Babylonians. The abacus is still in usetoday, principally in the far east. A modern abacus consists of rings that slide over rods, but theolder one pictured below dates from the time when pebbles were used for counting (the word"calculus" comes from the Latin word for pebble).

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A very old abacus

A more modern abacus. Note how the abacus is really just a representation of the humanfingers: the 5 lower rings on each rod represent the 5 fingers and the 2 upper rings

represent the 2 hands.

In 1617 an eccentric (some say mad) Scotsman named John Napier invented logarithms,which are a technology that allows multiplication to be performed via addition. The magicingredient is the logarithm of each operand, which was originally obtained from a printed table.But Napier also invented an alternative to tables, where the logarithm values were carved onivory sticks which are now called Napier's Bones.

An original set of Napier's Bones [photo courtesy IBM]

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A more modern set of Napier's Bones

Napier's invention led directly to the slide rule, first built in England in 1632 and still in use inthe 1960's by the NASA engineers of the Mercury, Gemini, and Apollo programs which landedmen on the moon.

A slide rule

Leonardo da Vinci (1452-1519) made drawings of gear-driven calculating machines butapparently never built any.

A Leonardo da Vinci drawing showing gears arranged for computing

The first gear-driven calculating machine to actually be built was probably the calculatingclock, so named by its inventor, the German professor Wilhelm Schickard in 1623. This device

got little publicity because Schickard died soon afterward in the bubonic plague.

Schickard's Calculating Clock

In 1642 Blaise Pascal, at age 19, invented the Pascaline as an aid for his father who was a taxcollector. Pascal built 50 of this gear-driven one-function calculator (it could only add) butcouldn't sell many because of their exorbitant cost and because they really weren't that accurate(at that time it was not possible to fabricate gears with the required precision). Up until thepresent age when car dashboards went digital, the odometer portion of a car's speedometerused the very same mechanism as the Pascaline to increment the next wheel after each fullrevolution of the prior wheel. Pascal was a child prodigy. At the age of 12, he was discovereddoing his version of Euclid's thirty-second proposition on the kitchen floor. Pascal went on to

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invent probability theory, the hydraulic press, and the syringe. Shown below is an 8 digit versionof the Pascaline, and two views of a 6 digit version:

Pascal's Pascaline [photo 2002 IEEE]

A 6 digit model for those who couldn't afford the 8 digit model

A Pascaline opened up so you can observe the gears and cylinders which rotated todisplay the numerical result

Click on the "Next" hyperlink below to read about the punched card system that was developedfor looms for later applied to the U.S. census and then to computers...

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John Kopplin 2002

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Just a few years after Pascal, the German Gottfried Wilhelm Leibniz (co-inventor with Newton ofcalculus) managed to build a four-function (addition, subtraction, multiplication, and division)calculator that he called the stepped reckonerbecause, instead of gears, it employed fluteddrums having ten flutes arranged around their circumference in a stair-step fashion. Althoughthe stepped reckoner employed the decimal number system (each drum had 10 flutes), Leibnizwas the first to advocate use of the binary number system which is fundamental to the operation

of modern computers. Leibniz is considered one of the greatest of the philosophers but he diedpoor and alone.

Leibniz's Stepped Reckoner (have you ever heard "calculating" referred to as"reckoning"?)

In 1801 the Frenchman Joseph Marie Jacquard invented a power loom that could base itsweave (and hence the design on the fabric) upon a pattern automatically read from punchedwooden cards, held together in a long row by rope. Descendents of thesepunched cards havebeen in use ever since (remember the "hanging chad" from the Florida presidential ballots of theyear 2000?).

Jacquard's Loom showing the threads and the punched cards

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By selecting particular cards for Jacquard's loom you defined the woven pattern [photo 2002 IEEE]

A close-up of a Jacquard card

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This tapestry was woven by a Jacquard loom

Jacquard's technology was a real boon to mill owners, but put many loom operators out of work.Angry mobs smashed Jacquard looms and once attacked Jacquard himself. History is full ofexamples of labor unrest following technological innovation yet most studies show that, overall,technology has actually increased the number of jobs.

By 1822 the English mathematician Charles Babbage was proposing a steam drivencalculating machine the size of a room, which he called the Difference Engine. This machinewould be able to compute tables of numbers, such as logarithm tables. He obtained governmentfunding for this project due to the importance of numeric tables in ocean navigation. Bypromoting their commercial and military navies, the British government had managed to becomethe earth's greatest empire. But in that time frame the British government was publishing aseven volume set of navigation tables which came with a companion volume of correctionswhich showed that the set had over 1000 numerical errors. It was hoped that Babbage'smachine could eliminate errors in these types of tables. But construction of Babbage'sDifference Engine proved exceedingly difficult and the project soon became the most expensivegovernment funded project up to that point in English history. Ten years later the device was still

nowhere near complete, acrimony abounded between all involved, and funding dried up. Thedevice was never finished.

A small section of the type of mechanism employed in Babbage's Difference Engine[photo 2002 IEEE]

Babbage was not deterred, and by then was on to his next brainstorm, which he calledthe Analytic Engine. This device, large as a house and powered by 6 steam engines, would bemore general purpose in nature because it would be programmable, thanks to the punched cardtechnology of Jacquard. But it was Babbage who made an important intellectual leap regardingthe punched cards. In the Jacquard loom, the presence or absence of each hole in the card

physically allows a colored thread to pass or stops that thread (you can see this clearly in theearlier photo). Babbage saw that the pattern of holes could be used to represent an abstractidea such as a problem statement or the raw data required for that problem's solution. Babbagesaw that there was no requirement that the problem matter itself physically pass thru the holes.

Furthermore, Babbage realized that punched paper could be employed as a storagemechanism, holding computed numbers for future reference. Because of the connection to theJacquard loom, Babbage called the two main parts of his Analytic Engine the "Store" and the"Mill", as both terms are used in the weaving industry. The Store was where numbers were held

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and the Mill was where they were "woven" into new results. In a modern computer these sameparts are called the memoryunitand the centralprocessingunit(CPU).

The Analytic Engine also had a key function that distinguishes computers from calculators: theconditional statement. A conditional statement allows a program to achieve different resultseach time it is run. Based on the conditional statement, the path of the program (that is, what

statements are executed next) can be determined based upon a condition or situation that isdetected at the very moment the program is running.

You have probably observed that a modern stoplight at an intersection between a busy streetand a less busy street will leave the green light on the busy street until a car approaches on theless busy street. This type of street light is controlled by a computer program that can sense theapproach of cars on the less busy street. That moment when the light changes from green tored is not fixed in the program but rather varies with each traffic situation. The conditionalstatement in the stoplight program would be something like, "if a car approaches on the lessbusy street and the more busy street has already enjoyed the green light for at least a minutethen move the green light to the less busy street". The conditional statement also allows aprogram to react to the results of its own calculations. An example would be the program that

the I.R.S uses to detect tax fraud. This program first computes a person's tax liability and thendecides whether to alert the police based upon how that person's tax payments compare to hisobligations.

Babbage befriended Ada Byron, the daughter of the famous poet Lord Byron (Ada would laterbecome the Countess Lady Lovelace by marriage). Though she was only 19, she wasfascinated by Babbage's ideas and thru letters and meetings with Babbage she learned enoughabout the design of the Analytic Engine to begin fashioning programs for the still unbuiltmachine. While Babbage refused to publish his knowledge for another 30 years, Ada wrote aseries of "Notes" wherein she detailed sequences of instructions she had prepared for the

Analytic Engine. The Analytic Engine remained unbuilt (the British government refused to getinvolved with this one) but Ada earned her spot in history as the first computer programmer. Ada

invented the subroutine and was the first to recognize the importance of looping. Babbagehimself went on to invent the modern postal system, cowcatchers on trains, and theophthalmoscope, which is still used today to treat the eye.

The next breakthrough occurred in America. The U.S. Constitution states that a census shouldbe taken of all U.S. citizens every 10 years in order to determine the representation of the statesin Congress. While the very first census of 1790 had only required 9 months, by 1880 the U.S.population had grown so much that the count for the 1880 census took 7.5 years. Automationwas clearly needed for the next census. The census bureau offered a prize for an inventor tohelp with the 1890 census and this prize was won by Herman Hollerith, who proposed and thensuccessfully adopted Jacquard's punched cards for the purpose of computation.

Hollerith's invention, known as the Hollerith desk, consisted of a card reader which sensed theholes in the cards, a gear driven mechanism which could count (using Pascal's mechanismwhich we still see in car odometers), and a large wall of dial indicators (a car speedometer is adial indicator) to display the results of the count.

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An operator working at a Hollerith Desk like the one below

Preparation of punched cards for the U.S. census

A few Hollerith desks still exist today [photo courtesy The Computer Museum]

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The patterns on Jacquard's cards were determined when a tapestry was designed and thenwere not changed. Today, we would call this a read-onlyform of information storage. Hollerithhad the insight to convert punched cards to what is today called a read/write technology. Whileriding a train, he observed that the conductor didn't merely punch each ticket, but ratherpunched a particular pattern of holes whose positions indicated the approximate height, weight,eye color, etc. of the ticket owner. This was done to keep anyone else from picking up a

discarded ticket and claiming it was his own (a train ticket did not lose all value when it waspunched because the same ticket was used for each leg of a trip). Hollerith realized how usefulit would be to punch (write) new cards based upon an analysis (reading) of some other set ofcards. Complicated analyses, too involved to be accomplished during a single pass thru thecards, could be accomplished via multiple passes thru the cards using newly printed cards toremember the intermediate results. Unknown to Hollerith, Babbage had proposed this longbefore.

Hollerith's technique was successful and the 1890 census was completed in only 3 years at asavings of 5 million dollars. Interesting aside: the reason that a person who removesinappropriate content from a book or movie is called a censor, as is a person who conducts acensus, is that in Roman society the public official called the "censor" had both of these jobs.

Hollerith built a company, the Tabulating Machine Company which, after a few buyouts,eventually became International Business Machines, known today as IBM. IBM grew rapidlyand punched cards became ubiquitous. Your gas bill would arrive each month with a punch cardyou had to return with your payment. This punch card recorded the particulars of your account:your name, address, gas usage, etc. (I imagine there were some "hackers" in these days whowould alter the punch cards to change their bill). As another example, when you entered a tollway (a highway that collects a fee from each driver) you were given a punch card that recordedwhere you started and then when you exited from the toll way your fee was computed basedupon the miles you drove. When you voted in an election the ballot you were handed was apunch card. The little pieces of paper that are punched out of the card are called "chad" andwere thrown as confetti at weddings. Until recently all Social Security and other checks issued

by the Federal government were actually punch cards. The check-out slip inside a library bookwas a punch card. Written on all these cards was a phrase as common as "close cover beforestriking": "do not fold, spindle, or mutilate". A spindle was an upright spike on the desk of anaccounting clerk. As he completed processing each receipt he would impale it on this spike.When the spindle was full, he'd run a piece of string through the holes, tie up the bundle, andship it off to the archives. You occasionally still see spindles at restaurant cash registers.

Two types of computer punch cards

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Incidentally, the Hollerith census machine was the first machine to ever be featured on amagazine cover.

Click on the "Next" hyperlink below to read about the first computers such as the Harvard Mark1, the German Zuse Z3 and Great Britain's Colossus...

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An Illustrated History of Computers

Part 3

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John Kopplin 2002

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IBM continued to develop mechanical calculators for sale to businesses to help withfinancial accounting and inventory accounting. One characteristic of both financialaccounting and inventory accounting is that although you need to subtract, you don'tneed negative numbers and you really don't have to multiply since multiplication can

be accomplished via repeated addition.

But the U.S. military desired a mechanical calculator more optimized for scientificcomputation. By World WarII the U.S. had battleships that could lob shells weighingas much as a small car over distances up to 25 miles. Physicists could write theequations that described how atmospheric drag, wind, gravity, muzzle velocity, etc.would determine the trajectory of the shell. But solving such equations was extremelylaborious. This was the work performed by the human computers. Their results would

be published in ballistic "firing tables" published in gunnery manuals. During WorldWarII the U.S. military scoured the country looking for (generally female) mathmajors to hire for the job of computing these tables. But not enough humans could befound to keep up with the need for new tables. Sometimes artillery pieces had to bedelivered to the battlefield without the necessary firing tables and this meant theywere close to useless because they couldn't be aimed properly. Faced with thissituation, the U.S. military was willing to invest in even hair-brained schemes toautomate this type of computation.

One early success was the HarvardMark Icomputer which was built as a partnershipbetween Harvard and IBM in 1944. This was the first programmable digital computermade in the U.S. But it was not a purely electronic computer. Instead the MarkI wasconstructed out of switches, relays, rotating shafts, and clutches. The machineweighed 5 tons, incorporated 500 miles of wire, was 8 feet tall and 51 feet long, andhad a 50 ft rotating shaft running its length, turned by a 5 horsepower electric motor.The MarkI ran non-stop for 15 years, sounding like a roomful of ladies knitting. Toappreciate the scale of this machine note the four typewriters in the foreground of the

following photo.

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The Harvard Mark I: an electro-mechanical computer

You can see the 50 ft rotating shaft in the bottom of the prior photo. This shaft was acentral power source for the entire machine. This design feature was reminiscent ofthe days when waterpower was used to run a machine shop and each lathe or othertool was driven by a belt connected to a single overhead shaft which was turned by an

outside waterwheel.

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A central shaft driven by an outside waterwheel and connected to each machine by overhead belts was the

customary power source for all the machines in a factory

Here's a close-up of one of the MarkI's four paper tape readers. A paper tape was animprovement over a box of punched cards as anyone who has ever dropped -- andthus shuffled -- his "stack" knows.

One of the four paper tape readers on the Harvard Mark I (you can observe the punched paper roll emerging

from the bottom)

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One of the primary programmers for the MarkI was a woman, Grace Hopper. Hopperfound the first computer "bug": a dead moth that had gotten into the MarkI and whosewings were blocking the reading of the holes in the paper tape. The word "bug" had

been used to describe a defect since at least 1889 but Hopper is credited with coiningthe word "debugging" to describe the work to eliminate program faults.

The first computer bug [photo 2002 IEEE]

In 1953 Grace Hopper invented the first high-level language, "Flow-matic". Thislanguage eventually became COBOL which was the language most affected by theinfamous Y2K problem. A high-level language is designed to be more understandable

by humans than is the binary language understood by the computing machinery. Ahigh-level language is worthless without a program -- known as a compiler-- to

translate it into the binary language of the computer and hence Grace Hopper alsoconstructed the world's first compiler. Grace remained active as a Rear Admiral in the

Navy Reserves until she was 79 (another record).

The MarkI operated on numbers that were 23 digits wide. It could add or subtract twoof these numbers in three-tenths of a second, multiply them in four seconds, anddivide them in ten seconds. Forty-five years later computers could perform an

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addition in a billionth of a second! Even though the MarkI had three quarters of amillion components, it could only store 72 numbers! Today, home computers canstore 30 million numbers in RAM and another 10 billion numbers on their hard disk.Today, a number can be pulled from RAM after a delay of only a few billionths of asecond, and from a hard disk after a delay of only a few thousandths of a second. This

kind of speed is obviously impossible for a machine which must move a rotating shaftand that is why electronic computers killed off their mechanical predecessors.

On a humorous note, the principal designer of the MarkI,Howard Aiken of Harvard,estimated in 1947 that six electronic digital computers would be sufficient to satisfythe computing needs of the entire United States. IBM had commissioned this study todetermine whether it should bother developing this new invention into one of itsstandard products (up until then computers were one-of-a-kind items built by specialarrangement). Aiken's prediction wasn't actually so bad as there were very fewinstitutions (principally, the government and military) that could afford the cost ofwhat was called a computer in 1947. He just didn't foresee the micro-electronics

revolution which would allow something like anIBM Stretch computer of 1959:

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(that's just the operator's console, here's the rest of its 33 foot length:)

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to be bested by a home computer of 1976 such as thisApple Iwhich sold for only$600:

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The Apple 1 which was sold as a do-it-yourself kit (without the lovely case seen here)

Computers had been incredibly expensive because they required so much hand

assembly, such as the wiring seen in this CDC7600:

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Typical wiring in an early mainframe computer [photo courtesy The Computer Museum]

The microelectronics revolution is what allowed the amount of hand-crafted wiringseen in the prior photo to be mass-produced as an integrated circuitwhich is a small

sliver of silicon the size of your thumbnail .

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An integrated circuit ("silicon chip") [photo courtesy of IBM]

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The primary advantage of an integrated circuit is not that the transistors (switches) areminiscule (that's the secondary advantage), but rather that millions of transistors can

be created and interconnected in a mass-production process. All the elements on theintegrated circuit are fabricated simultaneously via a small number (maybe 12) ofoptical masks that define the geometry of each layer. This speeds up the process of

fabricating the computer -- and hence reduces its cost -- just as Gutenberg's printingpress sped up the fabrication of books and thereby made them affordable to all.

The IBM Stretch computer of 1959 needed its 33 foot length to hold the 150,000transistors it contained. These transistors were tremendously smaller than the vacuumtubes they replaced, but they were still individual elements requiring individualassembly. By the early 1980s this many transistors could be simultaneously fabricatedon an integrated circuit. Today's Pentium 4 microprocessor contains 42,000,000

transistors in this same thumbnail sized piece of silicon.

It's humorous to remember that in between the Stretch machine (which would becalled a mainframe today) and the Apple I (a desktop computer) there was an entireindustry segment referred to as mini-computers such as the following PDP-12

computer of 1969:

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The DEC PDP-12

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Sure looks "mini", huh? But we're getting ahead of our story.

One of the earliest attempts to build an all-electronic (that is, no gears, cams, belts,shafts, etc.) digital computer occurred in 1937 by J. V. Atanasoff, a professor of

physics and mathematics at Iowa State University. By 1941 he and his graduate

student, Clifford Berry, had succeeded in building a machine that could solve 29simultaneous equations with 29 unknowns. This machine was the first to store data asa charge on a capacitor, which is how today's computers store information in theirmain memory (DRAMordynamic RAM). As far as its inventors were aware, it wasalso the first to employ binary arithmetic. However, the machine was not

programmable, it lacked a conditional branch, its design was appropriate for only onetype of mathematical problem, and it was not further pursued after World WarII. It'sinventors didn't even bother to preserve the machine and it was dismantled by those

who moved into the room where it lay abandoned.

The Atanasoff-Berry Computer [photo 2002 IEEE]

Another candidate for granddaddy of the modern computer was Colossus, built duringWorld WarII by Britain for the purpose of breaking the cryptographic codes used byGermany. Britain led the world in designing and building electronic machinesdedicated to code breaking, and was routinely able to read coded Germany radiotransmissions. But Colossus was definitely not a general purpose, reprogrammablemachine. Note the presence of pulleys in the two photos of Colossus below:

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Two views of the code-breaking Colossus of Great Britain

The Harvard MarkI, the Atanasoff-Berry computer, and the British Colossus all madeimportant contributions. American and British computer pioneers were still arguingover who was first to do what, when in 1965 the work of the German Konrad

Zuse was published for the first time in English. Scooped! Zuse had built a sequenceof general purpose computers in Nazi Germany. The first, theZ1, was built between

1936 and 1938 in the parlor of his parent's home.

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The Zuse Z1 in its residential setting

Zuse's third machine, theZ3, built in 1941, was probably the first operational,general-purpose, programmable (that is, software controlled) digital computer.Without knowledge of any calculating machine inventors since Leibniz (who lived inthe 1600's), Zuse reinvented Babbage's concept of programming and decided on hisown to employ binary representation for numbers (Babbage had advocated decimal).The Z3 was destroyed by an Allied bombing raid. The Z1 and Z2 met the same fateand the Z4 survived only because Zuse hauled it in a wagon up into the mountains.Zuse's accomplishments are all the more incredible given the context of the materialand manpower shortages in Germany during World WarII. Zuse couldn't even obtain

paper tape so he had to make his own by punching holes in discarded movie film.Because these machines were unknown outside Germany, they did not influence the

path of computing in America. But their architecture is identical to that still in usetoday: an arithmetic unit to do the calculations, a memory for storing numbers, acontrol system to supervise operations, and input and output devices to connect to theexternal world. Zuse also invented what might be the first high-level computer

language, "Plankalkul", though it too was unknown outside Germany.

Click on the "Next" hyperlink below to read about Eniac, Univac, IBM mainframes,and the IBM PC...



___________________________________

John Kopplin 2002

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The title of forefather of today's all-electronic digital computers is usually awardedto ENIAC, which stood for Electronic Numerical Integrator and Calculator. ENIACwas built at the University of Pennsylvania between 1943 and 1945 by two

professors, John Mauchly and the 24 year old J.PresperEckert, who got fundingfrom the war department after promising they could build a machine that would

replace all the "computers", meaning the women who were employed calculating thefiring tables for the army's artillery guns. The day that Mauchly and Eckert saw thefirst small piece of ENIAC work, the persons they ran to bring to their lab to show offtheir progress were some of these female computers (one of whom remarked, "I was

astounded that it took all this equipment to multiply 5 by 1000").

ENIAC filled a 20 by 40 foot room, weighed 30 tons, and used more than 18,000vacuum tubes. Like the MarkI, ENIAC employed paper card readers obtained fromIBM (these were a regular product forIBM, as they were a long established part of

business accounting machines, IBM's forte). When operating, the ENIAC was silentbut you knew it was on as the 18,000 vacuum tubes each generated waste heat like alight bulb and all this heat (174,000 watts of heat) meant that the computer could only

be operated in a specially designed room with its own heavy duty air conditioningsystem. Only the left half of ENIAC is visible in the first picture, the right half was

basically a mirror image of what's visible.

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Two views of ENIAC: the "Electronic Numerical Integrator and Calculator" (note that it wasn't even given

the name of computer since "computers" were people) [U.S. Army photo]

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To reprogram the ENIAC you had to rearrange the patch cords that you can observeon the left in the prior photo, and the settings of 3000 switches that you can observe

on the right. To program a modern computer, you type out a program with statementslike:

Circumference = 3.14 * diameter

To perform this computation on ENIAC you had to rearrange a large number of patchcords and then locate three particular knobs on that vast wall of knobs and set them to

3, 1, and 4.

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Reprogramming ENIAC involved a hike [U.S. Army photo]

Once the army agreed to fund ENIAC, Mauchly and Eckert worked around the clock,seven days a week, hoping to complete the machine in time to contribute to the war.Their war-time effort was so intense that most days they ate all 3 meals in thecompany of the army Captain who was their liaison with their military sponsors. Theywere allowed a small staff but soon observed that they could hire only the most juniormembers of the University of Pennsylvania staff because the more experienced

faculty members knew that their proposed machine would never work.

One of the most obvious problems was that the design would require 18,000 vacuum

tubes to all work simultaneously. Vacuum tubes were so notoriously unreliable thateven twenty years later many neighborhood drug stores provided a "tube tester" thatallowed homeowners to bring in the vacuum tubes from their television sets anddetermine which one of the tubes was causing their TV to fail. And television setsonly incorporated about 30 vacuum tubes. The device that used the largest number ofvacuum tubes was an electronic organ: it incorporated 160 tubes. The idea that 18,000tubes could function together was considered so unlikely that the dominant vacuumtube supplier of the day, RCA, refused to join the project (but did supply tubes in theinterest of "wartime cooperation"). Eckert solved the tube reliability problem throughextremely careful circuit design. He was so thorough that before he chose the type ofwire cabling he would employ in ENIAC he first ran an experiment where he starvedlab rats for a few days and then gave them samples of all the available types of cableto determine which they least liked to eat. Here's a look at a small number of thevacuum tubes in ENIAC:

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Even with 18,000 vacuum tubes, ENIAC could only hold 20 numbers at a time.However, thanks to the elimination of moving parts it ran much faster than the MarkI:

a multiplication that required 6 seconds on the MarkI could be performed on ENIACin 2.8 thousandths of a second. ENIAC's basic clock speed was 100,000 cycles persecond. Today's home computers employ clock speeds of 1,000,000,000 cycles persecond. Built with $500,000 from the U.S. Army, ENIAC's first task was to computewhether or not it was possible to build a hydrogen bomb (the atomic bomb wascompleted during the war and hence is older than ENIAC). The very first problem runon ENIAC required only 20 seconds and was checked against an answer obtainedafter forty hours of work with a mechanical calculator. After chewing on half a

million punch cards for six weeks, ENIAC did humanity no favor when it declared thehydrogen bomb feasible. This first ENIAC program remains classified even today.

Once ENIAC was finished and proved worthy of the cost of its development, itsdesigners set about to eliminate the obnoxious fact that reprogramming the computerrequired a physical modification of all the patch cords and switches. It took days tochange ENIAC's program. Eckert and Mauchly's next teamed up with the

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mathematician John von Neumann to design EDVAC, which pioneered the storedprogram. Because he was the first to publish a description of this new computer, vonNeumann is often wrongly credited with the realization that the program (that is, thesequence of computation steps) could be represented electronically just as the datawas. But this major breakthrough can be found in Eckert's notes long before he ever

started working with von Neumann. Eckert was no slouch: while in high schoolEckert had scored the second highest math SAT score in the entire country.

After ENIAC and EDVAC came other computers with humorous names such asILLIAC, JOHNNIAC, and, of course, MANIAC. ILLIAC was built at the UniversityofIllinois at Champaign-Urbana, which is probably why the science fiction authorArthur C. Clarke chose to have the HAL computer of his famous book "2001: ASpace Odyssey" born at Champaign-Urbana. Have you ever noticed that you can shift

each of the letters ofIBM backward by one alphabet position and get HAL?

ILLIAC II built at the University of Illinois (it is a good thing computers were one-of-a-kind creations in

these days, can you imagine being asked to duplicate this?)

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HAL from the movie "2001: A Space Odyssey". Look at the previous picture to understand why the movie

makers in 1968 assumed computers of the future would be things you walk into.

JOHNNIAC was a reference to John von Neumann, who was unquestionably agenius. At age 6 he could tell jokes in classical Greek. By 8 he was doing calculus. Hecould recite books he had read years earlier word for word. He could read a page of

the phone directory and then recite it backwards. On one occasion it took vonNeumann only 6 minutes to solve a problem in his head that another professor hadspent hours on using a mechanical calculator. Von Neumann is perhaps most famous(infamous?) as the man who worked out the complicated method needed to detonate

an atomic bomb.

Once the computer's program was represented electronically, modifications to thatprogram could happen as fast as the computer could compute. In fact, computerprograms could now modify themselves while they ran (such programs are called self-modifying programs). This introduced a new way for a program to fail: faulty logic in

the program could cause it to damage itself. This is one source of thegeneralprotection faultfamous in MS-DOS and the blue screen of death famous in

Windows.

Today, one of the most notable characteristics of a computer is the fact that its abilityto be reprogrammedallows it to contribute to a wide variety of endeavors, such as thefollowing completely unrelated fields:

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y the creation of special effects for movies,y the compression of music to allow more minutes of music to fit within the

limited memory of an MP3 player,y the observation of car tire rotation to detect and prevent skids in an anti-lock

braking system (ABS),y the analysis of the writing style in Shakespeare's work with the goal of proving

whether a single individual really was responsible for all these pieces.

By the end of the 1950's computers were no longer one-of-a-kind hand built devicesowned only by universities and government research labs. Eckert and Mauchly left theUniversity of Pennsylvania over a dispute about who owned the patents for theirinvention. They decided to set up their own company. Their first product was thefamous UNIVACcomputer, the first commercial (that is, mass produced) computer.In the 50's, UNIVAC (a contraction of "Universal Automatic Computer") was thehousehold word for "computer" just as "Kleenex" is for "tissue". The first UNIVACwas sold, appropriately enough, to the Census bureau. UNIVAC was also the firstcomputer to employ magnetic tape. Many people still confuse a picture of a reel-to-reel tape recorder with a picture of a mainframe computer.

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A reel-to-reel tape drive [photo courtesy ofThe Computer Museum]

ENIAC was unquestionably the origin of the U.S. commercial computer industry, butits inventors, Mauchly and Eckert, never achieved fortune from their work and their

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company fell into financial problems and was sold at a loss. By 1955 IBM was sellingmore computers than UNIVAC and by the 1960's the group of eight companies sellingcomputers was known as "IBM and the seven dwarfs". IBM grew so dominant thatthe federal government pursued anti-trust proceedings against them from 1969 to1982 (notice the pace of our country's legal system). You might wonder what type of

event is required to dislodge an industry heavyweight. In IBM's case it was their owndecision to hire an unknown but aggressive firm calledMicrosoftto provide thesoftware for theirpersonal computer(PC). This lucrative contract allowed Microsoftto grow so dominant that by the year 2000 their market capitalization (the total valueof their stock) was twice that ofIBM and they were convicted in Federal Court ofrunning an illegal monopoly.

If you learned computer programming in the 1970's, you dealt with what today arecalled mainframe computers, such as the IBM 7090 (shown below), IBM 360, orIBM 370.

The IBM 7094, a typical mainframe computer [photo courtesy of IBM]

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There were 2 ways to interact with a mainframe. The first was called timesharingbecause the computer gave each user a tiny sliver of time in a round-robin

fashion. Perhaps 100 users would be simultaneously logged on, each typing ona teletype such as the following:

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The Teletype was the standard mechanism used to interact with a time-sharing computer

A teletype was a motorized typewriter that could transmit your keystrokes to themainframe and then print the computer's response on its roll of paper. You typed asingle line of text, hit the carriage return button, and waited for the teletype to begin

noisily printing the computer's response (at a whopping 10 characters per second). Onthe left-hand side of the teletype in the prior picture you can observe a paper tape

reader and writer (i.e., puncher). Here's a close-up of paper tape:

Three views of paper tape

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After observing the holes in paper tape it is perhaps obvious why all computers usebinary numbers to represent data: a binary bit (that is, one digit of a binary number)can only have the value of 0 or 1 (just as a decimal digit can only have the value of 0

thru 9). Something which can only take two states is very easy to manufacture,control, and sense. In the case of paper tape, the hole has either been punched or it hasnot. Electro-mechanical computers such as the MarkI used relays to represent data

because a relay (which is just a motor driven switch) can only be open or closed. Theearliest all-electronic computers used vacuum tubes as switches: they too were eitheropen or closed. Transistors replaced vacuum tubes because they too could act as

switches but were smaller, cheaper, and consumed less power.

Paper tape has a long history as well. It was first used as an information storagemedium by Sir Charles Wheatstone, who used it to store Morse code that was arriving

via the newly invented telegraph (incidentally, Wheatstone was also the inventor ofthe accordion).

The alternative to time sharing was batch mode processing, where the computer givesits full attention to your program. In exchange for getting the computer's full attentionat run-time, you had to agree to prepare your program off-line on a key punch

machine which generated punch cards.

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An IBM Key Punch machine which operates like a typewriter except it produces punched cards rather than a

printed sheet of paper

University students in the 1970's bought blank cards a linear foot at a time from theuniversity bookstore. Each card could hold only 1 program statement. To submit your

program to the mainframe, you placed your stack of cards in the hopper of a cardreader. Your program would be run whenever the computer made it that far. Youoften submitted your deck and then went to dinner or to bed and came back laterhoping to see a successful printout showing your results. Obviously, a program run in

batch mode could not be interactive.

But things changed fast. By the 1990's a university student would typically own hisown computer and have exclusive use of it in his dorm room.

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The original IBM Personal Computer (PC)

This transformation was a result of the invention of the microprocessor. Amicroprocessor (uP) is a computer that is fabricated on an integrated circuit (IC).Computers had been around for 20 years before the first microprocessor wasdeveloped atIntelin 1971. The micro in the name microprocessor refers to the

physical size. Intel didn't invent the electronic computer. But they were the first tosucceed in cramming an entire computer on a single chip (IC). Intel was started in1968 and initially produced only semiconductor memory (Intel invented both theDRAM and the EPROM, two memory technologies that are still going strong today).In 1969 they were approached by Busicom, a Japanese manufacturer of high

performance calculators (these were typewriter sized units, the first shirt-pocket sizedscientific calculator was the Hewlett-Packard HP35 introduced in 1972). Busicomwanted Intel to produce 12 custom calculator chips: one chip dedicated to thekeyboard, another chip dedicated to the display, another for the printer, etc. Butintegrated circuits were (and are) expensive to design and this approach would haverequired Busicom to bear the full expense of developing 12 new chips since these 12

chips would only be of use to them.

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A typical Busicom desk calculator

But a new Intel employee (Ted Hoff) convinced Busicom to instead accept a generalpurpose computer chip which, like all computers, could be reprogrammed for manydifferent tasks (like controlling a keyboard, a display, a printer, etc.). Intel argued thatsince the chip could be reprogrammed for alternative purposes, the cost of developingit could be spread out over more users and hence would be less expensive to eachuser. The general purpose computer is adapted to each new purpose by writingaprogram which is a sequence of instructions stored in memory (which happened to

be Intel's forte). Busicom agreed to pay Intel to design a general purpose chip and toget a price break since it would allow Intel to sell the resulting chip to others. Butdevelopment of the chip took longer than expected and Busicom pulled out of the

project. Intel knew it had a winner by that point and gladly refunded all ofBusicom'sinvestment just to gain sole rights to the device which they finished on their own.

Thus became the Intel 4004, the first microprocessor (uP). The 4004 consisted of2300 transistors and was clocked at 108 kHz (i.e., 108,000 times per second).Compare this to the 42 million transistors and the 2 GHz clock rate (i.e.,2,000,000,000 times per second) used in a Pentium 4. One ofIntel's 4004 chips stillfunctions aboard the Pioneer 10 spacecraft, which is now the man-made objectfarthest from the earth. Curiously, Busicom went bankrupt and never ended up usingthe ground-breaking microprocessor.

Intel followed the 4004 with the 8008 and 8080. Intel priced the 8080 microprocessorat $360 dollars as an insult to IBM's famous 360 mainframe which cost millions ofdollars. The 8080 was employed in theMITS Altaircomputer, which was the world'sfirstpersonal computer(PC). It was personal all right: you had to build it yourselffrom a kit of parts that arrived in the mail. This kit didn't even include an enclosure

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and that is the reason the unit shown below doesn't match the picture on the magazine

cover.

The Altair 8800, the first PC

A Harvard freshman by the name ofBillGates decided to drop out of college so hecould concentrate all his time writing programs for this computer. This earlyexperienced put Bill Gates in the right place at the right time once IBM decided tostandardize on the Intel microprocessors for their line of PCs in 1981. The Intel

Pentium 4 used in today's PCs is still compatible with the Intel 8088 used in IBM'sfirst PC.

If you've enjoyed this history of computers, I encourage you to try your own hand atprogramming a computer. That is the only way you will really come to understand theconcepts of looping, subroutines, high and low-level languages, bits and bytes, etc. Ihave written a number of Windows programs which teach computer programming in afun, visually-engaging setting. I start my students on a programmable RPN calculatorwhere we learn about programs, statements, program and data memory, subroutines,logic and syntax errors, stacks, etc. Then we move on to an 8051 microprocessor

(which happens to be the most widespread microprocessor on earth) where we learnabout microprocessors, bits and bytes, assembly language, addressing modes, etc.Finally, we graduate to the most powerful language in use today: C++ (pronounced "C

plus plus"). These Windows programs are accompanied by a book's worth of on-linedocumentation which serves as a self-study guide, allowing you to teach yourselfcomputer programming! The home page (URL) for this collection of softwareis www.computersciencelab.com.

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Bibliography:

"ENIAC: The Triumphs and Tragedies of the World's First Computer" by ScottMcCartney.


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