Rear Admiral Grace Brewster Murray Hopper (born Grace Brewster Murray) (1906-1992) was an early computer programmer and the developer of the first compiler for a computer programming language. The compiler was known as the A compiler and its first version was A-0. Later versions were released commercially as the ARITH-MATIC, MATH-MATIC and FLOW-MATIC compilers.

She graduated from Vassar College with a bachelor's degree in mathematics and physics in 1928 and obtained her Ph.D. at Yale in 1934. By 1941 she was an associate professor at Vassar College. In 1943 she joined the US Navy and was assigned to work with Howard Aiken on the Mark I Calculator. She was the first person to write a program for it. At the end of the war she was discharged from the Navy, but she continued to work on the development of the Mark II and the Mark II Calculators.

In 1949 Hopper became an employee of the Eckert-Mauchley Computer Corporation and joined the team developing the UNIVAC I. In the early 1950s the company was taken over by the Remington Rand corporation and it was while she was working for them that her original compiler work was done.

Later she returned to the Navy where she worked on validation software for the programming language COBOL and its compiler. COBOL was defined by the CODASYL committee which extended her FLOW-MATIC language with some ideas from the IBM equivalent, COMTRAN. However, it was her great idea that programs could be written in a language that was close to English rather than in machine code or in languages close to machine code, such as the assemblers of the time. It is fair to say that COBOL was based very much on her philosophy.

Grace Hopper and associates, while working on a Mark II computer at Harvard University, discovered a moth stuck in a relay and thereby impeding operation, whereupon she remarked that they were "debugging" the system. Though the term 'bug' cannot be attributed to Admiral Hopper, this did bring the term computer 'bug' into popularity. The remains of the moth can be found in the group's log book at the Naval Surface Weapons Center.

Throughout much of her later career, Grace Hopper was much in demand as a speaker at various computer-related events. She was well-known for her lively and irreverant speaking style, as well as her rich treasury of old "war stories".

Grace Hopper is famous for her nanoseconds. People (such as generals and admirals) used to wonder why satellite communication took so long. She started handing out pieces of wire which were cut just under 1 foot long, which is the distance that light travels in 1 nanosecond (1 billionth of a second). The reason satellite communication is so slow is that the signal must travel for many nanoseconds on the way up, and then many nanoseconds on the way down. Even generals and admirals could understand this explanation. Later she used the same pieces of wire to illustrate why computers had to be small to be fast. At many of her talks, she handed out nanoseconds to everyone in the audience.

She retired from the Navy in 1986, and shortly thereafter was hired as a senior consultant to Digital Equipment Corporation, a position she retained until her death.

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