27.1: Fortran 95/2003/2008 Keywords

In programming, a keyword is a word or identifier that has a special Fortran 95/2003/2008 meaning. Keywords are reserved in that they cannot be used for anything else such variable names.

The Type as listed in the table refers to the following:

• statement \(\rightarrow\) implies a keyword that starts a statement, usually one line unless there is a continuation "&"
• construct \(\rightarrow\) implies multiple lines, usually ending with "end ..."
• attribute \(\rightarrow\) implies it is used in a statement to further clarify or specify additional information.

For reference, below is a partial list of keywords or reserved words. For a complete list of keywords, refer to the on-line GNU Fortran 95/2003/2008 documentation.

Keyword	Type	Meaning
allocatable	attribute	no space allocated here later allocate
allocate	statement	allocate memory space now for variable
assignment	attribute	means subroutine is assignment (=)
backspace	statement	back up one record
call	statement	call a subroutine
case	statement	used in select case structure
character	statement	intrinsic data type
close	statement	close a file
complex	statement	intrinsic data type
contains	statement	internal subroutines and functions follow
cycle	statement	continue the next iteration of a do loop (skipping the subsequent statements)
deallocate	statement	free up storage used by specified variable
default	statement	in a select case structure - all others
do	construct	start a do loop
else	construct	part of if, else if, else, end if
else if	construct	part of if, else if, else, end if
elsewhere	construct	part of where, elsewhere, end where
end do	construct	ends do loop
end function	construct	ends function
end if	construct	ends if
end interface	construct	ends interface
end module	construct	ends module
end program	construct	ends program
end select	construct	ends select case
end subroutine	construct	ends subroutine
end type	construct	ends type
end where	construct	ends where
endfile	statement	mark the end of a file
exit	statement	continue execution outside of a do loop
format	statement	defines a format
function	statement	starts the definition of a function
if	statement and construct	if(...) statement
implicit	statement	"none" is preferred to help find errors
in	a keyword for intent	the argument is read only
inout	a keyword for intent	the argument is read/write
integer	statement	intrinsic data type
intent	attribute	intent(in) or intent(out) or intent(inout)
interface	construct	begins an interface definition
intrinsic	statement	says that following names are intrinsic
inquire	statement	get the status of a unit
kind	attribute	sets the kind of the following variables
len	attribute	sets the length of a character string
logical	statement	intrinsic data type
module	construct	beginning of a module definition
namelist	statement	defines a namelist of input/output
nullify	statement	nullify a pointer
only	attribute	restrict what comes from a module
open	statement	open or create a file
operator	attribute	indicates function is an operator like +
optional	attribute	a parameter or argument is optional
out	a keyword for intent	the argument will be written
print	statement	performs output to screen
pointer	attribute	defined the variable as a pointer alias
private	statement and attribute	in a module
program	construct	start of a main program
public	statement and attribute	in a module - visible outside
read	statement	performs input
real	statement	intrinsic data type
recursive	attribute	allows functions and derived type recursion
result	attribute	allows naming of function result
return	statement	returns from exits subroutine or function
rewind	statement	move read or write position to beginning
select case	construct	start of a case construct
stop	statement	terminate execution of the main procedure
subroutine	construct	start of a subroutine definition
target	attribute	allows a variable to take a pointer alias
then	construct	part of if construct
type	construct	start of user defined type
use	statement	brings in a module
where	construct	conditional assignment
while	construct	a while form of a do loop
write	statement	performs output