Some of the FORTRAN basic terms and concepts are:
A program consists of one or more program units.
A program unit is a sequence of statements, terminated by an END.
A statement consists of zero or more key words, symbolic names, literal constants, statement labels, operators, and special characters.
Each key word, symbolic name, literal constant, and operator consists of one or more characters from the FORTRAN character set.
A character constant can include any valid ASCII character.
A statement label consists of 1 to 5 digits, with at least one nonzero.