Fortran_Standards

 The character set specified by the Fortran 95 and Fortran 90
 Standards consists of all uppercase and lowercase letters (A-Z and
 a-z), the digits 0-9, the underscore (_), and the following special
 characters:

         (blank or space)       :    (colon)
    =    (equal sign)           !    (exclamation point)
    +    (plus sign)            "    (quotation mark)       
    -    (minus sign)           %    (percent sign)  
    *    (asterisk)             &    (ampersand) 
    /    (slash)                ;    (semicolon)
    (    (left parenthesis)     <    (less than)
    )    (right parenthesis)    >    (greater than)
    ,    (comma)                ?    (question mark)
    .    (period)               $    (dollar sign)          
    '    (apostrophe)