A-0 System

The A-0 system (Arithmetic Language version 0) was an early tool made for the first electronic computers. It was created by Grace Murray Hopper in 1951 and 1952 for use with the UNIVAC I computer. Unlike compilers as we know them today, the A-0 system worked more like a loader or linker. People would write programs by listing subroutines and their arguments, with each subroutine given a number code. The A-0 system then turned these lists into machine code that the computer could run.

After the A-0, more advanced versions were developed, including the A-1, A-2, A-3 (called ARITH-MATIC), AT-3 (called MATH-MATIC), and B-0 (called FLOW-MATIC). The A-2 system, made in 1953 at the UNIVAC division of Remington Rand, was shared with customers, who could even send back improvements. This sharing of code was similar to today’s idea of free and open-source software, showing how early computer users worked together to improve technology.