Franz Leopold Alt was born and educated in Vienna, where he earned a PhD in mathematics from the University of Vienna in 1932. From 1923 to 1933 he was apprentice teacher at a secondary school and during the coming two years he was engaged in an unpaid research work. From 1935 to 1938 Alt was an actuary.
In May 1938, shortly after the annexation of Austria to Nazi Germany, Alt immigrated to the USA. From that year to 1946 he was researcher principal and later assistant director researcher at the Econometric Institute, New York. During World War II, from 1943 to 1945, he served in the US Army with the rank of Second Lieutenant.
From 1946 to 1948, Alt was department head of the computing laboratory of Ballistic Research Laboratories, Aberdeen. From 1948 to 1967 he worked with the National Bureau of Standards and from 1948 to 1952 also as assistant head of Computation Laboratories. From 1952 to 1962 he was assistant head of Applied Mathematical Division, during 1962-1963 head of Office of International Relations, and from 1964 to 1967 area manager for Information Systems designs and research office of standard reference data.
From 1954 to 1958 Alt was editor of Journal of Association Computer Machinery. As of the early 1960s he contributed to the Journal Research of the Natural Bureau of Standards, and to Advances in Computers. From 1960 to 1962 Franz Alt served as consultant at Management Scientific Research Group at the University of Maryland, and from 1967 to 1973 he was deputy director at Information Division of American Institute of Physics.
Franz Alt also taught mathematics at various universities. He specialized in computers and their applications in science, engineering, management and data processing. He also dealt with information retrieval, automatic language translations, numerical analytical operations research, econometrics, and geometry of metric spaces.
Franz Alt was a member of American Mathematicians Society; of Association for Computing Machinery, of which he president from 1950 to 1952 and chairman of the editorial board from 1954 to 1958. He was also a member of the National Research Council (1961-1964); Association for Computational Linguistics (v. president 1963-1964); American Standards Association Subcommittee (chairman 1963-65); International Council Scientific Unions-Data, and of International Task Groups on Computer Use in Data Centers. Franz Alt received First Winner of the Distinguished Service Award of the Association for Computing Machinery.
Franz Alt retired in 1973 and became active in various peace and justice organizations.