F is a modular, compiled, numeric programming language, designed for scientific programming and scientific computation. F was developed as a modern Fortran, thus making it a subset of Fortran 95. It combines both numerical and data abstraction features from these languages. F is also backwards compatible with Fortran 77, allowing calls to Fortran 77 programs. F was first included in the g95 compiler. Overview F is designed to be a minimal subset of Fortran, with only about one hundred intrinsic procedures. Language keywords and intrinsic function names are reserved keywords in F and no other names may take this exact form. F contains the same character set used in Fortran 90/95 with a limit of 132 characters. Reserved words are always written in lowercase. Any uppercase letter may appear in a character constant. Variable names do not have restriction and can include upper and lowercase characters. Operators F supports many of the standard operators used in Fortran. The operators supported by F are: Arithmetic operators: +, -, *, /, ** Relational operators: <, <=, ==, /=, >, >= Logical operators: .not., .and., .or., .eqv., .neqv. character concatenation: // The assignment operator is denoted by the equal sign =. In addition, pointer assignment is denoted by =>. Comments are denoted by the ! symbol: variable = expression ! assignment pointer => target ! pointer assignment Data types Similar to Fortran, the type specification is made up of a type, a list of attributes for the declared variables, and the variable list. F provides all the same types as Fortran as well, with the sole exception of doubles: ! type [,attribute list] :: entity declaration list real :: x, y ! declaring variables of type real x,y without an attribute list integer (kind = long), dimension (100) :: x ! declaring variable of type big integer array with the identifier x character (len = 100) :: student_name ! declaring a character type variable with len 100 F does not have intrinsic support for object-oriented programming, but it does allow for records: type, public :: City character (len = 100) :: name character (len = 50) :: state end type City Variable declarations are followed by an attribute list. The attributes allowed are parameter, public, private, allocatable, dimension, intent, optional, pointer, save and target. The attribute list is followed by ::, which is part of the syntax. F also allows for optional initialization