As the first UNIVAC was being developed, in 1949 Betty Holbertson developed the UNIVAC Instructions Code C-10. C-10 was the first software to allow a computer to be operated by keyboarded commands rather than dials and switches. It was also the first mnemonic code. Also in 1949, Grace Hopper left the Harvard Computation Laboratory to join Eckert-Mauchly Computer Corporation as a senior mathematician/programmer. In June 1949 John Mauchly conceived the Short Code—the first high-level programming language for an electronic computer—to be used with the BINAC. It was also the first interpreted language and the first assembly language. The Short Code first ran on UNIVAC I, serial 1, in 1950. [In 2005 no copies of the Short Code existed with dates earlier than 1952.]
In 1952 Grace Hopper wrote the first compiler (A-0) for UNIVAC, and on October 24, 1952 the UNIVAC Short Code II was developed. This was the earliest extant version of a high-level programming language actually intended to be used on an electronic digital computer.