Error F6987

[blueagle91]

I am new here, and i am new with FORTRAN. I hope i came to right place to ask a beginners question.
Here is my little code, what it does is not important some physics.
rogram zad87
implicit none
double precision,parameter :: m=5.98d24,g=6.672d11
double precision :: x
real :: r=6371,h
write(*,"(' Calculating h from 200 to 800 km')")

write (*,10) m,g
10 format (//,'result',//,&
3x,'Earth mass M=',d11.7,/,&
3x,'Constant G=',d11.7,//)

do h=200,800,50
x=-g*m/(r+h)**2

write(*,'(T2,f3,T18,d7.4)')h,x
end do

end program zad87

In attachent is image of program running. Now i know those stras means i need more space, but i have problem there too.
I have constanr m=5.98d24 when i put more places like d18.5 i get number .598000d25

And check the error belof F6987, i founded on net but i do not understand it.

I know C++ not FORTRAN so please help me.
It is program for school.

Thanks in advance.

 

[gullipe]

Hi bluagle91

Your output format was incorret or not wide enough. The programming was also rather "messy", so I made it more clear. Try the following program:

	program zad87

	implicit none

	real*8 m,g,x
	real*8 r,h

	m = 5.98 d24
	g = 6.672 d11
	r = 6371

	write (*,'(1x,a)') 'Calculating h from 200 to 800 km'

	write (*,'(1x,a)') 'Result'
	write (*,'(1x,a,1x,f30.2)') 'Earth mass M =', m
	write (*,'(1x,a,1x,f30.2)') 'Constant G =  ', g

	do h=200,800,50
	   x = -g*m/(r+h)**2
	   write(*,'(T2,f10.3,T10,d20.8)') h,x 
	enddo

	end

 

[blueagle91]

Thank you very much gullipe,
this is very helpful. Program works as it is expected to work.
I know it is messy, this are my first attempts, adapting to new language.
Thank you again.

 

[ArkM]

Never use real variables in iterative do loop header.
It does not conform to the modern Fortran standard.

 

[xwb]

The error code refers to your format in the write statement. It is printing H with format f3. Gullipe has changed this to f10.3 in the code reformat.

 

[gullipe]

hi blueagle91

You can find some information about Fortran errors (including the format error F6987) on:

http://terpconnect.umd.edu/~nsw/ench250/comp-err.htm

As ArkM points out, real variable in DO loops is not a modern Fortran standard. You can read some discussion about this on this forum on:

http://www.tek-tips.com/viewthread.cfm?qid=1572422