Evolution of Forth, The

Chuck Moore's Programming Language 1.1 Early Development Moore's programming career began in the late 1950's at the Smithsonian Astrophysical Observatory with programs to compute ephemerides, orbital elements, satellite station positions, etc. [Moore, 1958], [Veis, 1960]. His source code filled two card trays. To minimize recompiling this large program, he developed a simple interpreter to read cards controlling the program. This enabled him to compose different equations for several satellites without recompiling. This interpreter featured several commands and concepts that survived into modern Forth, principally a command to read "words" separated by spaces and one to convert numbers from external to internal form, plus an IF … ELSE construct. He found free-form input to be both more efficient (smaller and faster code) and reliable than the more common Fortran practice of formatting into specific columns, which had resulted in numerous re-runs due to mis-aligned columns.