Characters, Lexical Tokens, and Source Form

Topic describes the allowed characters, tokens, and source form information.

Characters Allowed in Names

Variables, named constants, program units, common blocks, procedures, arguments, constructs, derived types (types for structures), namelist groups, structure components, dummy arguments, and function results are among the elements in a program that have a name. As extensions, the Cray Fortran compiler permits the following characters in names:


`alphanumeric_character`	`currency_symbol`
`currency_symbol`	$

A name must begin with a letter and can consist of letters, digits, and underscores. The Cray Fortran compiler permits use of the dollar sign ($) in a name, but it cannot be the first character of a name.

Cray does not recommend using $ in user names because it can cause conflicts with the names of internal variables or library routines.

Switch Source Forms

The Cray Fortran compiler allows switching between fixed and free source forms within a source or include file by using the FIXED and FREE compiler directives.

Continuation Line Limit

The Cray Fortran compiler allows a statement to have an unlimited number of continuation lines. The Fortran standard allows only 255 continuation lines.

D Lines in Fixed Source Form

The Cray Fortran compiler allows a D or d character to occur in column one in fixed source form. Typically, the compiler treats a line with a D or d character in column one as a comment line. When the -e d command line option is in effect, however, the compiler replaces the D or d character with a blank and treats the rest of the line as a source statement. This can be used, for example, for debugging purposes if the rest of the line contains a PRINT statement.

This functionality is controlled through the -e d and -d d options on the compiler command line. For more information about these options, see the ftn(1) man page.