Version

1. Fortran77
2. F90/F95

Syntax

1. not case sensitive
2. 6 spaces; max 72 width
3. c for comment
4. & or * at 6th space for continue

5. program and subroutine

    program my_prog
   
    end
   
    subroutine my_sub
   
    end
   

Declare

REAL
INTEGER
COMPLEX
DOUBLE PRECISION: real*8
DOUBLE COMPLEX
CHARACTER

IMPLICIT NONE : add to the beginning of each sub(program)

w = dble(x) * dble(y)

CONSTANTS

1.0
2.0E6
.TRUE.
.FALSE.

INPUT/OUTPUT

READ(*,*) NAME
WRITE(*,*) 'THE HELLO'
WRITE(*,*) 'NAME IS ', NAME

CONDITION

if (condition) print *, ' '

if (x .lt. 0) then
   statements
else if (logical) then
   statements2
else
   statements3
end if

LOOP

Do i=1, 10, 2
	blabla
end do

Do while
    statements
end do

use exit to exit loop

MATH

**: exponential
DOT_PRODUCT(vecA, vecB)
MATMUL(matA, matB)

COMPARE

.GT.
.GE.
.EQ.
.LE.
.LT.
.NE.

If (A .LT. 0.0) A = (-1)*A

If () THEN
	JJJ
ELSE
    JJJ
END IF

.AND.
.OR.
.NOT.

FILE

OPEN (UNIT=10,FILE='MY_DATA.DAT') # other than 5,6
READ(10, *) A
write(10, *) B
close(10)

PROGRAM

program name
declaration
statements
stop
end

Compile

gfortran(f77) test.f -o test.out
./test.out

FUNCTION

1. function has a type
2. return a value with same name
3. called by name and parameters
4. can use return like a go to statement, and there can be more than one return
5. end at the end
6. call by value

7. can be after the write statement

    real function r(m,t)
    integer m
    real t
   
    r = 0.1*t * (m**2 + 14*m + 46)
    if (r .LT. 0) r = 0.0
    return
    end
   
    type function name (list-of-variables)
    declarations
    statements
    return
    end
   

8. can also return array value reference

    function polynomialMult(npts,x,y)
    integer npts
    double precision x(npts), results(npts + 1), y(npts,npts)
   
    ! Change the next line to whatever you want
    double precision, dimension(npts) :: polynomialMult
   
    polynomialMult =  x(1:npts) + 1
   
    end function
   

9. Passing the sizes of arrays into subroutines is very FORTRAN77 and almost always unnecessary now.

SUBROUTINE

1. can return more than 1 value (array)
2. no type
3. should not be declared in the calling program unit
4. called by call
5. call by reference
6. must be a stand alone statement

Subroutine has RETURN

subroutine my_sub(a, b)

return
end

call mysub

Progress Bar

Revised from http://thelazycatholic.wordpress.com/2010/08/19/progress-bar-in-fortran/

  subroutine progress(j, n)

  implicit none
  integer(kind=4) :: j,k,n
  character(len=18) :: bar="\r???% |          |"

  ! updates the fraction of calculation done
  write(unit=bar(2:4),fmt="(i3)") 100*j/n
  do k = 1, j*10/n
     bar(7+k:7+k)="*"
  enddo

  ! print the progress bar.
  write(*,'(a)',advance='no') bar

  return
  end

then call from main function:

call progress(iter, niter)

Matrix

A(1, :) for 1st row

stop

stop 0 : to stop and return message
call exit(1)

Troublesome

1. need to declare sub function in function or subroutine

Reference

1. http://www.stanford.edu/class/me200c/tutorial_77/