Fortran Elements and Concepts
This section provides definitions for the various elements of a Fortran program. The Fortran language is written using a specific set of characters that form the words, numbers, names, and expressions that make up Fortran statements. These statements form a Fortran program. The Fortran character set, the rules for writing Fortran statements, the main structural elements of a program, and the proper order of statements in a program are also discussed in this section. Fortran Character Set
The Fortran character set consists of 26 uppercase and 26 lowercase letters (alphabetic characters), the numbers 0 through 9 (digits), and special characters. This manual refers to letters (uppercase and lowercase) together with the underscore (_) as extended alphabetic characters. The extended alphabetic characters together with the digits are also referred to as alphanumeric characters. The complete character set is
Letters: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
a b c d e f g h i j k l m n o p q r s t u v w x y z
Digits: 0 1 2 3 4 5 6 7 8 9
( Left parenthesis
) Right parenthesis
. Decimal point
$ Currency symbol
! Exclamation point
" Quotation mark
Lowercase alphabetic characters, the exclamation point (!), the underscore (_), and the double quote (") are extensions to Fortran 77. Digits are interpreted in base 10. A special character can serve as an operator, a part of a character constant, a part of a numeric constant, or some other function
Use blank characters freely to improve the appearance and readability of Fortran statements. They have no significance in Fortran statements, except
- in character constants
- for H and character editing in format specifications
- in Hollerith constants
- to signify an initial line when used in column 6 of source line
- when counting the total number of characters allowed in any one Statement
These special considerations are discussed in detail in later sections.
Table lists escape sequences for representing non-graphic characters and for compatibility with the C programming language.
Table : C Escape Sequences
The compiler treats the backslash character as the beginning of an escape sequence by default. To use backslash as a normal character, compile the program with the –backslash option.