27.1: Fortran 95/2003/2008 Keywords
- Page ID
- 54813
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)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 |
| 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 |