After the end of the war, Bartik went on to work with the ENIAC designers John Eckert and John Mauchly, and helped them develop the BINAC and UNIVAC I computers. BINAC was the first computer to use magnetic tape instead of punch cards to store data and the first computer to utilize the twin unit concept. The BINAC, which was the first stored program computer hardware wise, worked successfully. BINAC was purchased by Northrop Aircraft to guide the Snark missile, but the BINAC proved to be too large for their purposes. However, according to a Northrop Aircraft programmer, despite claims that the BINAC didn't work once it was moved to Northrop Aircraft were erroneous and the BINAC was working well into the mid-1950s. Besides, BINAC, Jean's more important work involved her responsibilities in designing the UNIVAC's logic circuits among other UNIVAC programming and design tasks. Bartik also co-programmed with her life-long friend Betty Holberton the first generative programming system (SORT/MERGE) for a computer. Recalling her time working with Eckert and Mauchly on these projects, she described their close group of computer engineers as a "technical Camelot."