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Grace Hopper

Original nameGrace Hopper

American Computer Scientist and Navy Rear Admiral, Pioneer of the Compiler and High-Level Programming Language

Those Who Turned Invention Into Industry · Industry-Builders

The CompilerThe COBOL LanguagePopularizing the Word "Debugging"

Who they are

Grace Hopper (1906–1992) was an American mathematician and computer scientist who joined the US Naval Reserve during World War II, thereafter took part in programming the early computer Mark I, and was one of the very few women in a core technical post in the early development of computer science. Her most pioneering contribution was proposing and realizing the concept of the "compiler" — a software tool that automatically translates human-readable high-level-language instructions into machine code the computer can directly execute; before this, programmers had to write instructions directly line by line in obscure machine or assembly language, and the compiler’s appearance greatly lowered the technical threshold of writing computer programs, letting more people without low-level hardware expertise take part in software development. She thereafter directed the design of the COBOL programming language, oriented to business data processing and using a syntax close to natural English, which for decades after was one of the most widely used programming languages in the core systems of banks, insurance, and other financial industries worldwide, with a great body of legacy systems still running on COBOL code today. Hopper is also famed for popularizing the terms "bug" and "debugging" in computing — by tradition she once took a real moth crushed dead in the relay of a faulty computer and taped it in her work log as the record of "the first real bug found."

Primary sourcesGrace Hopper’s US Navy service recordsOriginal design documents of the COBOL programming language

Key stories

The First "Bug" Ever Recorded

In 1947 the Mark II computer maintained by Hopper’s team ran abnormally, and investigation found the cause was a moth crushed dead between the contacts of a relay, causing a short circuit; the team carefully removed the moth and taped it in the work-log book, noting "first actual bug found," and this anecdote was thereafter widely spread, the terms "bug" and "debugging," used sporadically in engineering before, thereby widely popularized and fixed in computing through this vivid anecdote.

Letting the Computer "Understand" Instructions Close to English

Hopper firmly believed a programming language should be as close as possible to the expression of human natural language rather than obscure symbols only professional engineers could read, and the COBOL language she directed the design of used many keywords and sentence structures close to English syntax, a design idea that greatly lowered the learning threshold of writing programs for technical staff in business and finance; COBOL thereafter became for decades the most widely adopted programming language in the core transaction systems of banks worldwide, and to this day trillions of financial transactions still rely on legacy systems running on COBOL code.

Relationships

Mentor

💻Alan Turing

Disciple

🌙Margaret Hamilton 🪟Bill Gates

Echoes today

Below are how modern works borrow or reinterpret this name or story — not the original material. The two differ, so keep them apart.

The popularization of the terms "bug" and "debugging"Though "bug" was used sporadically for a mechanical fault as early as Edison’s time, the real-moth anecdote Hopper’s team recorded greatly sped the popularization and fixing of "bug" and "debugging" in computing, still used today.

The US Navy destroyer USS Grace HopperThe US Navy named an Arleigh Burke-class guided-missile destroyer the USS Grace Hopper, commemorating her outstanding contribution to computer science and US naval technology.

Appears in

The Birth of the Computer and the Information AgeThe Stored Program, Cybernetics, and the First "Bug"

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