In 1949, she joined the Eckert–Mauchly Computer Corporation and was part of the team that developed the UNIVAC I computer. At Eckert–Mauchly she managed the development of one of the first COBOL compilers. She believed that programming should be simplified with an English based computer programming language. Her compiler converted English terms into machine code understood by computers. By 1952, Hopper had finished her program linker (originally called a compiler), which was written for the A-0 System.During her wartime service, she co-authored three papers based on her work on the Harvard Mark 1. She is accredited with writing the first computer manual, “A Manual of Operation for the Automatic Sequence Controlled Calculator.”