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Illustration by Ario Murti

Programming Pioneer

Meet the woman who taught us how to talk to computers

By Dani Leviss
Lexile: 920L; 610L
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Illustration of a person programming

Illustration by Ario Murti

Early computers, like this one used by Grace Hopper, could fill an entire room.

As you read, think about how Grace Hopper’s work in coding lives on today.

Old computer coding

B Christopher/Alamy Stock Photo

The pattern of holes on this tape told early computers what to do. Computers carried out the instructions one line at a time.

Anyone who has used computers knows that they don’t always work the way they’re supposed to! When a computer has an error, it’s often called a . That term became popular after an incident in 1947 during a computer repair by computer scientist Grace Hopper. Back then, Hopper and her team were fixing a broken computer when they found an actual bug—a moth—inside it! 

The computer that Hopper was working on was one of the first in the U.S. It looked nothing like today’s computers. It filled a room at Harvard University in Cambridge, Massachusetts.

While serving in the U.S. Navy, Hopper had solved math equations with computers. At the time, many nations were fighting in World War II. Some of Hopper’s calculations helped to end the war. But that’s not all this trailblazer did.

Coding for Her Country

Sailors saluting an older person

Peter Southwick/AP Images

Sailors salute Rear Admiral Hopper before her retirement ceremony in 1986.

When the U.S. entered World War II, Hopper, a math and physics expert, wanted to serve her country. At first, the Navy rejected the 34-year-old Hopper for being too old and too petite. But she continued to apply, and in 1943, she left her job as a professor to join the Navy.

In 1944, Hopper joined a team using an early electric computer, the Mark I. Computers were new inventions then. They were designed to solve complex calculations quickly. Before computers, people did calculations for things like weather forecasting and navigation by hand.

Hopper, a Navy lieutenant, was one of the first women to become a computer coder. Coders , or give instructions to, computers. Instead of typing on a computer’s keyboard like coders do today, Hopper had to punch out her code as lines of holes on paper tape. This tape was fed into the computer, which read it as instructions. Hopper programmed the Mark I to calculate missile paths and prepare ships to find and disarm underwater bombs.

Computer Speak

Black & white photo of soldiers and a teacher in a classroom

© HAGLEY MUSEUM AND ARCHIVE/SCIENCE SOURCE

Hopper teaches military members COBOL, a computer language she helped invent in 1959.

After Hopper mastered the Mark I, she wrote the first computer manual in 1946. She included pieces of code that could be adapted for different purposes. Coders continue to share code with others today. 

In 1951, Hopper invented a program that changed English commands into , the language of computers. That helped more people communicate with computers. As companies built computers that used different coding languages, Hopper helped create a coding language that let computers talk to each other. 

After retiring in 1986, Hopper gave lectures about computers until her death at age 85. “If you ask me what I’m most proud of,” she once said, “the answer would be all the young people I’ve trained over the years.”

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