This summary was extracted from various sources. It is not intended to be 100% complete. Hopefully it will be useful as a memory aid in writing Fortran programs.
Brought to you by ANSI committee X3J3 and ISO-IEC/JTC1/SC22/WG5 (Fortran) This is neither complete nor precisely accurate, but hopefully, after a small investment of time it is easy to read and very useful. This is the free form version of Fortran, no statement numbers, no C in column 1, start in column 1 (not column 7), typically indent 2, 3, or 4 spaces per each structure. The typical extension is .f90 . Continue a statement on the next line by ending the previous line with an ampersand & . Start the continuation with & for strings. The rest of any line is a comment starting with an exclamation mark ! . Put more than one statement per line by separating statements with a semicolon ; . Null statements are OK, so lines can end with semicolons. Separate words with space or any form of "white space" or punctuation.
means fill in something appropriate for xxx and do not type the "<" or ">" . ... ellipsis means the usual, fill in something, one or more lines [stuff] means supply nothing or at most one copy of "stuff" [stuff1 [stuff2]] means if "stuff1" is included, supply nothing or at most one copy of stuff2. "old" means it is in the language, like almost every feature of past Fortran standards, but should not be used to write new programs.
programusually file name is .f90 use bring in any needed modules implicit none good for error detection order is important, no more declarations end program block data old common, dimension, equivalence now obsolete end block data module bring back in with use implicit none good for error detection can have private and public and interface end module subroutine use: call to execute implicit none good for error detection end subroutine subroutine (par1, par2, ...) use: call (arg1, arg2,... ) to execute implicit none optional, good for error detection par1, par2, ... are defined in declarations and can be specified in, inout, pointer, etc. return optional, end causes automatic return entry (par...) old, optional other entries end subroutine function (par1, par2, ...) result( ) use: (arg1, arg2, ... argn) as variable implicit none optional, good for error detection rslt, par1, ... are defined in declarations = required somewhere in execution [return] optional, end causes automatic return end function old function(...) use: (arg1, arg2, ... argn) as variable = required somewhere in execution [return] optional, end causes automatic return end function
will mean exactly one statement in this section a construct is multiple lines
There are five (5) basic types: integer, real, complex, character and logical. There may be any number of user derived types. A modern (not old) declaration starts with a type, has attributes, then ::, then variable(s) names integer i, pivot, query old integer, intent (inout) :: arg1 integer (selected_int_kind (5)) :: i1, i2 integer, parameter :: m = 7 integer, dimension(0:4, -5:5, 10:100) :: A3D double precision x old real (selected_real_kind(15,300) :: x complex :: z logical, parameter :: what_if = .true. character, parameter :: me = "Jon Squire" typea new user type, derived type declarations end type type ( ) :: stuff declaring stuff to be of derived type real, dimension(:,:), allocatable, target :: A real, dimension(:,:), pointer :: P Attributes may be: allocatable no memory used here, allocate later dimension vector or multi dimensional array external will be defined outside this compilation intent argument may be in, inout or out intrinsic declaring function to be an intrinsic optional argument is optional parameter declaring a constant, can not be changed later pointer declaring a pointer private in a module, a private declaration public in a module, a public declaration save keep value from one call to the next, static target can be pointed to by a pointer Note: not all combinations of attributes are legal
note: "statement" means key word that starts a statement, one line
unless there is a continuation "&"
"construct" means multiple lines, usually ending with "end ..."
"attribute" means it is used in a statement to further define
"old" means it should not be used in new code
allocatable attribute, no space allocated here, later allocate
allocate statement, allocate memory space now for variable
assign statement, old, assigned go to
assignment attribute, means subroutine is assignment (=)
block data construct, old, compilation unit, replaced by module
call statement, call a subroutine
case statement, used in select case structure
character statement, basic type, intrinsic data type
common statement, old, allowed overlaying of storage
complex statement, basic type, intrinsic data type
contains statement, internal subroutines and functions follow
continue statement, old, a place to put a statement number
cycle statement, continue the next iteration of a do loop
data statement, old, initialized variables and arrays
deallocate statement, free up storage used by specified variable
default statement, in a select case structure, all others
do construct, start a do loop
double precision statement, old, replaced by selected_real_kind(15,300)
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 block data construct, old, ends block data
end do construct, ends do
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
entry statement, old, another entry point in a procedure
equivalence statement, old, overlaid storage
exit statement, continue execution outside of a do loop
external attribute, old statement, means defines else where
function construct, starts the definition of a function
go to statement, old, requires fixed form statement number
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, basic type, 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
kind attribute, sets the kind of the following variables
len attribute, sets the length of a character string
logical statement, basic type, intrinsic data type
module construct, beginning of a module definition
namelist statement, defines a namelist of input/output
nullify statement, nullify(some_pointer) now points nowhere
only attribute, restrict what comes from a module
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
parameter attribute, old statement, makes variable real only
pause old, replaced by stop
pointer attribute, defined the variable as a pointer alias
private statement and attribute, in a module, visible inside
program construct, start of a main program
public statement and attribute, in a module, visible outside
real statement, basic type, intrinsic data type
recursive attribute, allows functions and derived type recursion
result attribute, allows naming of function result result(Y)
return statement, returns from, exits, subroutine or function
save attribute, old statement, keep value between calls
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 part of if construct
type construct, start of user defined type
type ( ) statement, declaration of a variable for a users type
use statement, brings in a module
where construct, conditional assignment
while construct, a while form of a do loop
backspace statement, back up one record close statement, close a file endfile statement, mark the end of a file format statement, old, defines a format inquire statement, get the status of a unit open statement, open or create a file print statement, performs output to screen read statement, performs input rewind statement, move read or write position to beginning write statement, performs output
** exponentiation * multiplication / division + addition - subtraction // concatenation == .eq. equality /= .ne. not equal < .lt. less than > .gt. greater than <= .le. less than or equal >= .ge. greater than or equal .not. complement, negation .and. logical and .or. logical or .eqv. logical equivalence .neqv. logical not equivalence, exclusive or .eq. == equality, old .ne. /= not equal. old .lt. < less than, old .gt. > greater than, old .le. <= less than or equal, old .ge. >= greater than or equal, old Other punctuation: / ... / used in data, common, namelist and other statements (/ ... /) array constructor, data is separated by commas 6*1.0 in some contexts, 6 copies of 1.0 (i:j:k) in some contexts, a list i, i+k, i+2k, i+3k, ... i+nk<=j (:j) j and all below (i:) i and all above (:) undefined or all in range
Logical constants:
.true. True
.false. False
Integer constants:
0 1 -1 123456789
Real constants:
0.0 1.0 -1.0 123.456 7.1E+10 -52.715E-30
Complex constants:
(0.0, 0.0) (-123.456E+30, 987.654E-29)
Character constants:
"ABC" "a" "123'abc$%#@!" " a quote "" "
'ABC' 'a' '123"abc$%#@!' ' a apostrophe '' '
Derived type values:
type name
character (len=30) :: last
character (len=30) :: first
character (len=30) :: middle
end type name
type address
character (len=40) :: street
character (len=40) :: more
character (len=20) :: city
character (len=2) :: state
integer (selected_int_kind(5)) :: zip_code
integer (selected_int_kind(4)) :: route_code
end type address
type person
type (name) lfm
type (address) snail_mail
end type person
type (person) :: a_person = person( name("Squire","Jon","S."), &
address("106 Regency Circle", "", "Linthicum", "MD", 21090, 1936))
a_person%snail_mail%route_code == 1936
open ()
open (unit=, file=, iostat=)
open (unit=, ... many more, see below )
close ()
close (unit=, iostat=,
err=, status="KEEP")
read ()
read (unit=, fmt=, iostat=,
end=, err=)
read (unit=, rec=)
write ()
format an explicit format can replace * in any
I/O statement. Include the format in
apostrophes or quotes and keep the parenthesis.
examples:
print "(3I5,/(2X,3F7.2/))",
Intrinsic Functions are presented in alphabetical order and then grouped
by topic. The function name appears first. The argument(s) and result
give an indication of the type(s) of argument(s) and results.
[,dim=] indicates an optional argument "dim".
"mask" must be logical and usually conformable.
"character" and "string" are used interchangeably.
A brief description or additional information may appear.
Intrinsic Functions (alphabetical):
abs(integer_real_complex) result(integer_real_complex)
achar(integer) result(character) integer to character
acos(real) result(real) arccosine |real| <= 1.0 0<=result<=Pi
adjustl(character) result(character) left adjust, blanks go to back
adjustr(character) result(character) right adjust, blanks to front
aimag(complex) result(real) imaginary part
aint(real [,kind=]) result(real) truncate to integer toward zero
all(mask [,dim]) result(logical) true if all elements of mask are true
allocated(array) result(logical) true if array is allocated in memory
anint(real [,kind=]) result(real) round to nearest integer
any(mask [,dim=}) result(logical) true if any elements of mask are true
asin(real) result(real) arcsine |real| <= 1.0 -Pi/2<=result<=Pi/2
associated(pointer [,target=]) result(logical) true if pointing
atan(real) result(real) arctangent -Pi/2<=result<=Pi/2
atan2(y=real,x=real) result(real) arctangent -Pi<=result<=Pi
bit_size(integer) result(integer) size in bits in model of argument
btest(i=integer,pos=integer) result(logical) true if pos has a 1, pos=0..
ceiling(real) result(real) truncate to integer toward infinity
char(integer [,kind=]) result(character) integer to character [of kind]
cmplx(x=real [,y=real] [kind=]) result(complex) x+iy
conjg(complex) result(complex) reverse the sign of the imaginary part
cos(real_complex) result(real_complex) cosine
cosh(real) result(real) hyperbolic cosine
count(mask [,dim=]) result(integer) count of true entries in mask
cshift(array,shift [,dim=]) circular shift elements of array, + is right
date_and_time([date=] [,time=] [,zone=] [,values=]) y,m,d,utc,h,m,s,milli
dble(integer_real_complex) result(real_kind_double) convert to double
digits(integer_real) result(integer) number of bits to represent model
dim(x=integer_real,y=integer_real) result(integer_real) proper subtraction
dot_product(vector_a,vector_b) result(integer_real_complex) inner product
dprod(x=real,y=real) result(x_times_y_double) double precision product
eoshift(array,shift [,boundary=] [,dim=]) end-off shift using boundary
epsilon(real) result(real) smallest positive number added to 1.0 /= 1.0
exp(real_complex) result(real_complex) e raised to a power
exponent(real) result(integer) the model exponent of the argument
floor(real) result(real) truncate to integer towards negative infinity
fraction(real) result(real) the model fractional part of the argument
huge(integer_real) result(integer_real) the largest model number
iachar(character) result(integer) position of character in ASCII sequence
iand(integer,integer) result(integer) bit by bit logical and
ibclr(integer,pos) result(integer) argument with pos bit cleared to zero
ibits(integer,pos,len) result(integer) extract len bits starting at pos
ibset(integer,pos) result(integer) argument with pos bit set to one
ichar(character) result(integer) pos in collating sequence of character
ieor(integer,integer) result(integer) bit by bit logical exclusive or
index(string,substring [,back=]) result(integer) pos of substring
int(integer_real_complex) result(integer) convert to integer
ior(integer,integer) result(integer) bit by bit logical or
ishft(integer,shift) result(integer) shift bits in argument by shift
ishftc(integer, shift) result(integer) shift circular bits in argument
kind(any_intrinsic_type) result(integer) value of the kind
lbound(array,dim) result(integer) smallest subscript of dim in array
len(character) result(integer) number of characters that can be in argument
len_trim(character) result(integer) length without trailing blanks
lge(string_a,string_b) result(logical) string_a>=string_b
lgt(string_a,string_b) result(logical) string_a>string_b
lle(string_a,string_b) result(logical) string_a<=string_b
llt(string_a,string_b) result(logical) string_a<= 1.0 0<=result<=Pi
aimag(complex) result(real) imaginary part
aint(real [,kind=]) result(real) truncate to integer toward zero
anint(real [,kind=]) result(real) round to nearest integer
asin(real) result(real) arcsine |real| <= 1.0 -Pi/2<=result<=Pi/2
atan(real) result(real) arctangent -Pi/2<=result<=Pi/2
atan2(y=real,x=real) result(real) arctangent -Pi<=result<=Pi
ceiling(real) result(real) truncate to integer toward infinity
cmplx(x=real [,y=real] [kind=]) result(complex) x+iy
conjg(complex) result(complex) reverse the sign of the imaginary part
cos(real_complex) result(real_complex) cosine
cosh(real) result(real) hyperbolic cosine
dble(integer_real_complex) result(real_kind_double) convert to double
digits(integer_real) result(integer) number of bits to represent model
dim(x=integer_real,y=integer_real) result(integer_real) proper subtraction
dot_product(vector_a,vector_b) result(integer_real_complex) inner product
dprod(x=real,y=real) result(x_times_y_double) double precision product
epsilon(real) result(real) smallest positive number added to 1.0 /= 1.0
exp(real_complex) result(real_complex) e raised to a power
exponent(real) result(integer) the model exponent of the argument
floor(real) result(real) truncate to integer towards negative infinity
fraction(real) result(real) the model fractional part of the argument
huge(integer_real) result(integer_real) the largest model number
int(integer_real_complex) result(integer) convert to integer
log(real_complex) result(real_complex) natural logarithm
log10(real) result(real) logarithm base 10
matmul(matrix,matrix) result(vector_matrix) on integer_real_complex_logical
max(a1,a2,a3,...) result(integer_real) maximum of list of values
maxexponent(real) result(integer) maximum exponent of model type
maxloc(array [,mask=]) result(integer_vector) indices in array of maximum
maxval(array [,dim=] [,mask=]) result(array_element) maximum value
min(a1,a2,a3,...) result(integer-real) minimum of list of values
minexponent(real) result(integer) minimum(negative) exponent of model type
minloc(array [,mask=]) result(integer_vector) indices in array of minimum
minval(array [,dim=] [,mask=]) result(array_element) minimum value
mod(a=integer_real,p) result(integer_real) a modulo p
modulo(a=integer_real,p) result(integer_real) a modulo p
nearest(real,direction) result(real) nearest value toward direction
nint(real [,kind=]) result(real) round to nearest integer value
product(array [,dim=] [,mask=]) result(integer_real_complex) product
radix(integer_real) result(integer) radix of integer or real model, 2
random_number(harvest=real_out) subroutine, uniform random number 0 to 1
random_seed([size=] [,put=] [,get=]) subroutine to set random number seed
range(integer_real_complex) result(integer_real) decimal exponent of model
real(integer_real_complex [,kind=]) result(real) convert to real
rrspacing(real) result(real) reciprocal of relative spacing of model
scale(real,integer) result(real) multiply by 2**integer
set_exponent(real,integer) result(real) put integer as exponent of real
sign(integer_real,integer_real) result(integer_real) sign of second on first
sin(real_complex) result(real_complex) sine of angle in radians
sinh(real) result(real) hyperbolic sine of argument
spacing(real) result(real) spacing of model numbers near argument
sqrt(real_complex) result(real_complex) square root of argument
sum(array [,dim=] [,mask=]) result(integer_real_complex) sum of elements
tan(real) result(real) tangent of angle in radians
tanh(real) result(real) hyperbolic tangent of angle in radians
tiny(real) result(real) smallest positive model representation
transpose(matrix) result(matrix) the transpose of a matrix
Intrinsic Functions (Logical and bit)
all(mask [,dim]) result(logical) true if all elements of mask are true
any(mask [,dim=}) result(logical) true if any elements of mask are true
bit_size(integer) result(integer) size in bits in model of argument
btest(i=integer,pos=integer) result(logical) true if pos has a 1, pos=0..
count(mask [,dim=]) result(integer) count of true entries in mask
iand(integer,integer) result(integer) bit by bit logical and
ibclr(integer,pos) result(integer) argument with pos bit cleared to zero
ibits(integer,pos,len) result(integer) extract len bits starting at pos
ibset(integer,pos) result(integer) argument with pos bit set to one
ieor(integer,integer) result(integer) bit by bit logical exclusive or
ior(integer,integer) result(integer) bit by bit logical or
ishft(integer,shift) result(integer) shift bits in argument by shift
ishftc(integer, shift) result(integer) shift circular bits in argument
logical(logical [,kind=]) convert to logical
matmul(matrix,matrix) result(vector_matrix) on integer_real_complex_logical
merge(true_source,false_source,mask) result(source_type) choose by mask
mvbits(from,frompos,len,to,topos) result(integer) move bits
not(integer) result(integer) bit by bit logical complement
transfer(source,mold [,size]) result(mold_type) same bits, new type
intrinsic Functions (Character or string)
achar(integer) result(character) integer to character
adjustl(character) result(character) left adjust, blanks go to back
adjustr(character) result(character) right adjust, blanks to front
char(integer [,kind=]) result(character) integer to character [of kind]
iachar(character) result(integer) position of character in ASCII sequence
ichar(character) result(integer) pos in collating sequence of character
index(string,substring [,back=]) result(integer) pos of substring
len(character) result(integer) number of characters that can be in argument
len_trim(character) result(integer) length without trailing blanks
lge(string_a,string_b) result(logical) string_a>=string_b
lgt(string_a,string_b) result(logical) string_a>string_b
lle(string_a,string_b) result(logical) string_a<=string_b
llt(string_a,string_b) result(logical) string_a
Last updated 9/21/98