No abstract

This paper describes the design of a programming language suitable for writing portable, machine independent programs. Based on Fortran, and implemented at the lowest level by means of subprograms, this language (PFortran) provides features which allow programs to be designed so as to be rather insensitive to computer architecture (byte versus word addressable) or to main memory size.The complete syntax of PFortran is currently being developed, and a PFortran-to-Fortran compiler is being written. This paper describes a PFortran program after compilation: as a pure Fortran program utilizing a special library of service subprograms.PFortran includes the features of: machine independent I/O, data compression/decompression, virtual data arrays (having generalized subscript forms), variable precision arithmetic, and a programmercontrolled data unit called the kernel which acts like a variable-sized byte or word.The PFortran compiler will be written in Fortran. Its output will be directly compilable using a wide range of existing standard Fortran compilers for specific machines. The support library routines are written in Fortran and assembly language, and designed for rapid conversion to most machines.