Grace Hopper was a computer scientist and U.S. Navy Rear Admiral whose genius made programming accessible. She was a pioneer of the Harvard Mark I computer and believed that computer code should be written in English rather than mathematical symbols. To achieve this, she invented the first 'compiler'—a program that translates human-readable code into machine language. This breakthrough led to the development of COBOL, which became the most widely used programming language for business in the 20th century. Hopper is also famously credited with 'debugging' after finding a literal moth in a computer relay. Her work laid the foundation for all modern high-level programming languages.