In today’s digital world, it’s easy for just about anyone to create a mobile app or write software, thanks to Java, JavaScript, Python, and other programming languages.

But that wasn’t always the case. Because the primary language of computers is binary code, early programmers used punch cards to instruct computers what tasks to complete. Each hole represented a single binary digit.

That changed in 1952 with the A-0 compiler, a series of specifications that automatically translates high-level languages such as English into machine-readable binary code.

The compiler, now an IEEE Milestone, was developed by Grace Hopper, who worked as a senior mathematician at the Eckert-Mauchly Computer Corp., now part of Unisys, in Philadelphia.

IEEE Fellow’s innovation allowed programmers to write code faster and easier using English commands. For her, however, the most important outcome was the influence it had on the development of modern programming languages, making writing code more accessible to everyone, according to a Penn Engineering Today article.

The dedication of the A-0 compiler as an IEEE Milestone was held in Philadelphia on 7 May at the University of Pennsylvania. That’s where the Eckert-Mauchly Computer Corp. got its start.

“This milestone celebrates the first step of applying computers to automate the tedious portions of their own programming,” André DeHon, professor of electrical systems, engineering, and computer science, said at the dedication ceremony.

Eliminating the punch-card system

To program a computer, early technicians wrote out tasks in assembly language—a human-readable way to write machine code, which is made up of binary numbers. They then manually translated the assembly language into machine code and punched holes representing the binary digits into cards, according to a Medium article on the method. The cards were fed into a machine that read the holes and input the data into the computer.

The punch-card system was laborious; it could take days to complete a task. The cards couldn’t be used with even a slight defect such as a bent corner. The method also had a high risk of human error.

After leading the development of the Electronic Numerical Integrator and Computer (ENIAC) at Penn, computer scientists J. Presper Eckert and John W. Mauchly set about creating a replacement for punch cards. ENIAC was built to improve the accuracy of U.S. artillery during World War II, but the two men wanted to develop computers for commercial applications, according to a Pennsylvania Center for the Book article.

The machine they designed was the first known large-scale electronic computer, the Universal Automatic, or UNIVAC I. Hopper was on its development team.

UNIVAC I used 6,103 vacuum tubes and took up a 33-square-meter room. The machine had a memory unit. Instead of punch cards, the computer used magnetic tape to input data. The tapes, which could hold audio, video, and written data, were up to 457 meters long. Unlike previous computers, the UNIVAC I had a keyboard so an operator could input commands, according to the Pennsylvania Center for the Book article.

“This milestone celebrates the first step of applying computers to automate the tedious portions of their own programming.” —André DeHon

Technicians still had to manually feed instructions into the computer, however, to run any new program.

That time-consuming process led to errors because “programmers are lousy copyists,” Hopper said in a speech for the Association for Computing Machinery. “It was amazing how many times a 4 would turn into a delta, which was our space symbol, or into an A. Even B’s turned into 13s.”

According to a Hidden Heroes article, Hopper had an idea for simplifying programming: Have the computer translate English to machine code.

She was inspired by computer scientist Betty Holberton’s sort/merge generator and Mauchly’s Short Code. Holberton is one of six women who programmed the ENIAC to calculate artillery trajectories in seconds, and she worked alongside Hopper on the UNIVAC I. Her sort/merge program, invented in 1951 for the UNIVAC I, handled the large data files stored on magnetic tapes. Hopper defined the sort/merge program as the first version of virtual memory because it made use of overlays automatically without being directed to by the programmer, according to a Stanford presentation about programming languages. The Short Code, which was developed in the 1940s, allowed technicians to write programs using brief sequences of English words corresponding directly to machine code instructions. It bridged the gap between human-readable code and machine-executable instructions.

“I think the first step to tell us that we could actually use a computer to write programs was the sort/merge generator,” Hopper said in the presentation. “And Short Code was the first step in moving toward something which gave a programmer the actual power to write a program in a language which bore no resemblance whatsoever to the original machine code.”

IEEE Fellow Grace Hopper inputting call numbers into the Universal Automatic (UNIVAC I), which allows the computer to find the correct instructions to complete. The A-0 compiler translates the English instructions into machine-readable binary code.Computer History Museum

Easier, faster, and more accurate programming

Hopper, who figured computers should speak human-like languages, rather than requiring humans to speak computer languages, began thinking about how to allow programmers to call up specific codes using English, according to an IT Professional profile.

But she needed a library of frequently used instructions for the computer to reference and a system to translate English to machine code. That way, the computer could understand what task to complete.

Such a library didn’t exist, so Hopper built her own. It included tapes that held frequently used instructions for tasks that she called subroutines. Each tape stored one subroutine, which was assigned a three-number call sign so that the UNIVAC I could locate the correct tape. The numbers represented sets of three memory addresses: one for the memory location of the subroutine, another for the memory location of the data, and the third for the output location, according to the Stanford presentation.

“All I had to do was to write down a set of call numbers, let the computer find them on the tape, and do the additions,” she said in a Centre for Computing History article. “This was the first compiler.”

The system was dubbed the A-0 compiler because code was written in one language, which was then “compiled” into a machine language.

What previously had taken a month of manual coding could now be done in five minutes, according to a Cockroach Labs article.

Hopper presented the A-0 to Eckert-Mauchly Computer executives. Instead of being excited, though, they said they didn’t believe a computer could write its own programs, according to the article.

“I had a running compiler, and nobody would touch it, because they carefully told me computers could only do arithmetic; they could not do programs,” Hopper said. “It was a selling job to get people to try it. I think with any new idea, because people are allergic to change, you have to get out and sell the idea.”

It took two years for the company’s leadership to accept the A-0.

In 1954, Hopper was promoted to director of automatic programming for the UNIVAC division. She went on to create the first compiler-based programming languages including Flow-Matic, the first English language data-processing compiler. It was used to program UNIVAC I and II machines.

Hopper also was involved in developing COBOL, one of the earliest standardized computer languages. It enabled computers to respond to words in addition to numbers, and it is still used in business, finance, and administrative systems. Hopper’s Flow-Matic formed the foundation of COBOL, whose first specifications were made available in 1959.

A plaque recognizing the A-0 is now displayed at the University of Pennsylvania. It reads:

During 1951–1952, Grace Hopper invented the A-0 Compiler, a series of specifications that functioned as a linker/loader. It was a pioneering achievement of automatic programming as well as a pioneering utility program for the management of subroutines. The A-0 Compiler influenced the development of arithmetic and business programming languages. This led to COBOL (Common Business-Oriented Language), becoming the dominant high-level language for business applications.

The IEEE Philadelphia Section sponsored the nomination.

Administered by the IEEE History Center and supported by donors, the Milestone program recognizes outstanding technical developments worldwide.

About Grace Hopper

Hopper didn’t start as a computer programmer. She was a mathematician at heart, earning bachelor’s degrees in mathematics and physics in 1928 from Vassar College, in Poughkeepsie, N.Y. She then received master’s and doctoral degrees in mathematics and mathematical physics from Yale in 1930 and 1934, respectively.

She taught math at Vassar, but after the bombing of Pearl Harbor and the U.S. entry into World War II, Hopper joined the war effort. She took a leave of absence from Vassar to join the U.S. Naval Reserve (Women’s Reserve) in December 1943. She was assigned to the Bureau of Ships Computation Project at Harvard, where she worked for mathematician Howard Aiken. She was part of Aiken’s team that developed the Mark I, one of the earliest electromechanical computers. Hopper was the third person and the first woman to program the machine.

After the war ended, she became a research fellow at the Harvard Computation Laboratory. In 1946 she joined the Eckert-Mauchly Computer Corp., where she worked until her retirement in 1971. During 1959 she was an adjunct lecturer at Penn’s Moore School of Electrical Engineering.

Her work in programming earned her the nickname “Amazing Grace,” according to an entry about her on the Engineering and Technology History Wiki.

Hopper remained a member of the Naval Reserve and, in 1967, was recalled to active duty. She led the effort to standardize programming languages for the military, according to the ETHW entry. She was eventually promoted to rear admiral. When she retired from the Navy at the age of 79 in 1989, she was the oldest serving officer in all the U.S. armed forces.

Among her many honors was the 1991 U.S. National Medal of Technology and Innovation “for her pioneering accomplishments in the development of computer programming languages that simplified computer technology and opened the door to a significantly larger universe of users.”

She received 40 honorary doctorates from universities, and the Navy named a warship in her honor.

The semiconductor laser, invented more than 60 years ago, is the foundation of many of today’s technologies including barcode scanners, fiber-optic communications, medical imaging, and remote controls. The tiny, versatile device is now an IEEE Milestone.

The possibilities of laser technology had set the scientific world alight in 1960, when the laser, long described in theory, was first demonstrated. Three U.S. research centers unknowingly began racing each other to create the first semiconductor version of the technology. The three—General Electric, IBM’s Thomas J. Watson Research Center, and the MIT Lincoln Laboratory—independently reported the first demonstrations of a semiconductor laser, all within a matter of days in 1962.

The semiconductor laser was dedicated as an IEEE Milestone at three ceremonies, with a plaque marking the achievement installed at each facility. The Lincoln Lab event is available to watch on demand.

Invention of the laser spurs a three-way race

The core concept of the laser dates back to 1917, when Albert Einstein theorized about “stimulated emission.” Scientists already knew electrons could absorb and emit light spontaneously, but Einstein posited that electrons could be manipulated to emit at a particular wavelength. It took decades for engineers to turn his theory into reality.

In the late 1940s, physicists were working to improve the design of a vacuum tube used by the U.S. military in World War II to detect enemy planes by amplifying their signals. Charles Townes, a researcher at Bell Labs in Murray Hill, N.J., was one of them. He proposed creating a more powerful amplifier that passed a beam of electromagnetic waves through a cavity containing gas molecules. The beam would stimulate the atoms in the gas to release their energy exactly in step with the beam’s waves, creating energy that allowed it to exit the cavity as a much more powerful beam.

In 1954 Townes, then a physics professor at Columbia, created the device, which he called a “maser” (short for microwave amplification by stimulated emission of radiation). It would prove an important precursor to the laser.

Many theorists had told Townes his device couldn’t possibly work, according to an article published by the American Physical Society. Once it did work, the article says, other researchers quickly replicated it and began inventing variations.

Townes and other engineers figured that by harnessing higher-frequency energy, they could create an optical version of the maser that would generate beams of light. Such a device potentially could generate more powerful beams than were possible with microwaves, but it also could create beams of varied wavelengths, from the infrared to the visible. In 1958 Townes published a theoretical outline of the “laser.”

“It’s amazing what these … three organizations in the Northeast of the United States did 62 years ago to provide all this capability for us now and into the future.”

Several teams worked to fabricate such a device, and in May 1960 Theodore Maiman, a researcher at Hughes Research Lab, in Malibu, Calif., built the first working laser. Maiman’s paper, published in Nature three months later, described the invention as a high-power lamp that flashed light onto a ruby rod placed between two mirrorlike silver-coated surfaces. The optical cavity created by the surfaces oscillated the light produced by the ruby’s fluorescence, achieving Einstein’s stimulated emission.

The basic laser was now a reality. Engineers quickly began creating variations.

Many perhaps were most excited by the potential for a semiconductor laser. Semiconducting material can be manipulated to conduct electricity under the right conditions. By its nature, a laser made from semiconducting material could pack all the required elements of a laser—a source of light generation and amplification, lenses, and mirrors—into a micrometer-scale device.

“These desirable attributes attracted the imagination of scientists and engineers” across disciplines, according to the Engineering and Technology History Wiki.

A pair of researchers discovered in 1962 that an existing material was a great laser semiconductor: gallium arsenide.

Gallium-arsenide was ideal for a semiconductor laser

On 9 July 1962, MIT Lincoln Laboratory researchers Robert Keyes and Theodore Quist told the audience at the Solid State Device Research Conference that they were developing an experimental semiconductor laser, IEEE Fellow Paul W. Juodawlkis said during his speech at the IEEE Milestone dedication ceremony at MIT. Juodawlkis is director of the MIT Lincoln Laboratory’s quantum information and integrated nanosystems group.

The laser wasn’t yet emitting a coherent beam, but the work was advancing quickly, Keyes said. And then Keyes and Quist shocked the audience: They said they could prove that nearly 100 percent of the electrical energy injected into a gallium-arsenide semiconductor could be converted into light.

MIT’s Lincoln Laboratory’s [from left] Robert Keyes, Theodore M. Quist, and Robert Rediker testing their laser on a TV set.MIT Lincoln Laboratory

No one had made such a claim before. The audience was incredulous—and vocally so.

“When Bob [Keyes] was done with his talk, one of the audience members stood up and said, ‘Uh, that violates the second law of thermodynamics,’” Juodawlkis said.

The audience erupted into laughter. But physicist Robert N. Hall—a semiconductor expert working at GE’s research laboratory in Schenectady, N.Y.—silenced them.

“Bob Hall stood up and explained why it didn’t violate the second law,” Juodawlkis said. “It created a real buzz.”

Several teams raced to develop a working semiconductor laser. The margin of victory ultimately came down to a few days.

A ‘striking coincidence’

A semiconductor laser is made with a tiny semiconductor crystal that is suspended inside a glass container filled with liquid nitrogen, which helps keep the device cool. General Electric Research and Development Center/AIP Emilio Segrè Visual Archives

Hall returned to GE, inspired by Keyes and Quist’s speech, certain that he could lead a team to build an efficient, effective gallium arsenide laser.

He had already spent years working with semiconductors and invented what is known as a “p-i-n” diode rectifier. Using a crystal made of purified germanium, a semiconducting material, the rectifier could convert AC to DC—a crucial development for solid-state semiconductors used in electrical transmission.

That experience helped accelerate the development of semiconductor lasers. Hall and his team used a similar setup to the “p-i-n” rectifier. They built a diode laser that generated coherent light from a gallium arsenide crystal one-third of one millimeter in size, sandwiched into a cavity between two mirrors so the light bounced back and forth repeatedly. The news of the invention came out in the November 1, 1962, Physical Review Letters.

As Hall and his team worked, so did researchers at the Watson Research Center, in Yorktown Heights, N.Y. In February 1962 Marshall I. Nathan, an IBM researcher who previously worked with gallium arsenide, received a mandate from his department director, according to ETHW: Create the first gallium arsenide laser.

Nathan led a team of researchers including William P. Dumke, Gerald Burns, Frederick H. Dill, and Gordon Lasher, to develop the laser. They completed the task in October and hand-delivered a paper outlining their work to Applied Physics Letters, which published it on 1 November 1962.

Over at MIT’s Lincoln Laboratory, Quist, Keyes, and their colleague Robert Rediker published their findings in Applied Physics Letters on 1 December1962.

It had all happened so quickly that a New York Times article marveled about the “striking coincidence,” noting that IBM officials didn’t know about GE’s success until GE sent invitations to a news conference. An MIT spokesperson told the Times that GE had achieved success “a couple days or a week” before its own team.

Both IBM and GE had applied for U.S. patents in October, and both were ultimately awarded.

All three facilities now have been honored by IEEE for their work.

“Perhaps nowhere else has the semiconductor laser had greater impact than in communications,” according to an ETHW entry, “where every second, a semiconductor laser quietly encodes the sum of human knowledge into light, enabling it to be shared almost instantaneously across oceans and space.”

IBM Research’s semiconductor laser used a gallium arsenide p-n diode, which was patterned into a small optical cavity with an etched mesa structure.IBM

Juodawlkis, speaking at the Lincoln Lab ceremony, noted that semiconductor lasers are used “every time you make a cellphone call” or “Google silly cat videos.”

“If we look in the broader world,” he said, “semiconductor lasers are really one of the founding pedestals of the information age.”

He concluded his speech with a quote summing up a 1963 Time magazine article: “If the world is ever afflicted with a choice between thousands of different TV programs, a few diodes with their feeble beams of infrared light might carry them all at once.”

That was a “prescient foreshadowing of what semiconductor lasers have enabled,” Juodawlkis said. “It’s amazing what these … three organizations in the Northeast of the United States did 62 years ago to provide all this capability for us now and into the future.”

Plaques recognizing the technology are now displayed at GE, the Watson Research Center, and the Lincoln Laboratory. They read:

In the autumn of 1962, General Electric’s Schenectady and Syracuse facilities, IBM Thomas J. Watson Research Center, and MIT Lincoln Laboratory each independently reported the first demonstrations of the semiconductor laser. Smaller than a grain of rice, powered using direct current injection, and available at wavelengths spanning the ultraviolet to the infrared, the semiconductor laser became ubiquitous in modern communications, data storage, and precision measurement systems.

The IEEE Boston, New York, and Schenectady sections sponsored the nomination.

Administered by the IEEE History Center and supported by donors, the Milestone program recognizes outstanding technical developments around the world.

Edith Clarke was a powerhouse in practically every sense of the word. From the start of her career at General Electric in 1922, she was determined to develop stable, more reliable power grids.

And Clarke succeeded, playing a critical role in the rapid expansion of the North American electric grid during the 1920s and ’30s.

During her first years at GE she invented what came to be known as the Clarke calculator. The slide rule let engineers solve equations involving electric current, voltage, and impedance 10 times faster than by hand.

Her calculator and the power distribution methods she developed paved the way for modern grids. She also worked on hydroelectric power plant designs, according to a 2022 profile in Hydro Review.

She broke down barriers during her life. In 1919 she became the first woman to earn a master’s degree in electrical engineering from MIT. Three years later, she became the first woman in the United States to work as an electrical engineer.

Her life is chronicled in Edith Clarke: Trailblazer in Electrical Engineering. Written by Paul Lief Rosengren, the book is part of IEEE-USA’s Famous Women Engineers in History series.

Becoming the first female electrical engineer

Clarke was born in 1883 in the small farming community of Ellicott City, Md. At the time, few women attended college, and those who did tended to be barred from taking engineering classes. She was orphaned at 12, according to Sandy Levins’s Wednesday’s Women website. After high school, Clarke used a small inheritance from her parents to attend Vassar, a women’s college in Poughkeepsie, N.Y., where she earned a bachelor’s degree in mathematics and astronomy in 1908. Those degrees were the closest equivalents to an engineering degree available to Vassar students at the time.

In 1912 Clarke was hired by AT&T in New York City as a computing assistant. She worked on calculations for transmission lines and electric circuits. During the next few years, she developed a passion for power engineering. She enrolled at MIT in 1918 to further her career, according to her Engineering and Technology History Wiki biography.

After graduating, though, she had a tough time finding a job in the man-dominated field. After months of applying with no luck, she landed a job at GE in Boston, where she did more or less the same work as she did in her previous role at AT&T, except now as a supervisor. Clarke led a team of computers—employees (mainly women) who performed long, tedious calculations by hand before computing machines became widely available.

The Clarke Calculator let engineers solve equations involving electric current, voltage, and impedance 10 times faster than by hand. Clarke was granted a U.S. patent for the slide rule in 1925.Science History Images/Alamy

While at GE she developed her calculator, eventually earning a patent for it in 1925.

In 1921 Clarke left GE to become a full-time physics professor at Constantinople Women’s College, in what is now Istanbul, according to a profile by the Edison Tech Center. But she returned to GE a year later when it offered her a salaried electrical engineering position in its Central Station Engineering department in Boston.

Although Clarke didn’t earn the same pay or enjoy the same prestige as her male colleagues, the new job launched her career.

U.S. power grid pioneer

According to Rosengren’s book, during Clarke’s time at GE, transmission lines were getting longer and larger power loads were increasing the chances of instability. Mathematical models for assessing grid reliability at the time were better suited to smaller systems.

To model systems and power behavior, Clarke created a technique using symmetrical components—a method of converting three-phase unbalanced systems into two sets of balanced phasors and a set of single-phase phasors. The method allowed engineers to analyze the reliability of larger systems.

Vivien Kellems [left] and Clarke, two of the first women to become a full voting member of the American Institute of Electrical Engineers, meeting for the first time in GE’s laboratories in Schenectady, N.Y. Bettmann/Getty Images

Clarke described the technique in “Steady-State Stability in Transmission Systems,” which was published in 1925 in A.I.E.E. Transactions, a journal of the American Institute of Electrical Engineers, one of IEEE’s predecessors. Clarke had scored another first: the first woman to have her work appear in the journal.

In the 1930s, Clarke designed the turbine system for the Hoover Dam, a hydroelectric power plant on the Colorado River between Nevada and Arizona. The electricity it produced was stored in massive GE generators. Clarke’s pioneering system later was installed in similar power plants throughout the western United States.

Clarke retired in 1945 and bought a farm in Maryland. She came out of retirement two years later and became the first female electrical engineering professor in the United States when she joined the University of Texas, Austin. She retired for good in 1956 and returned to Maryland, where she died in 1959.

First female IEEE Fellow

Clarke’s pioneering work earned her several recognitions never before bestowed on a woman. She was the first woman to become a full voting member of the AIEE and its first female Fellow, in 1948.

She received the 1954 Society of Women Engineers Achievement Award “in recognition of her many original contributions to stability theory and circuit analysis.” She was posthumously elected in 2015 to the National Inventors Hall of Fame.