forums.silverfrost.com

[christyleomin]

I've just started programming in Fortran 90 and have some fundamental questions;

1) I want to comment several lines (i.e. block comment) in my program.I have been commenting single lines using !. Is there a possibility of doing a block comment? That is comenting several successive lines instead of inserting an ! in every line?

2) This is a simple one again;

I have got

code
subroutine A

---------
end subroutine A

PROGRAM MYPROGRAM

REAL*8 X

PRINT*, 'X'

READ*, X

call subroutine A

end POGRAM MYPROGRAM
end code

Now, I do not want to pass X to my subroutine A.I presume X is a global variable , so it should be visible to my subroutine A even if it is not passed as an argument. Right?

3) I want to learn about debugging in Fortran 90.Any references in the web (simple and good) will be really appreciated.

[IanLambley]

1. Not that I know or use - just keep using !
2. Two ways, the old fashioned common block or a new fangled module. The common block way is:

[LitusSaxonicum]

Sometimes you don't need comments.

I come from the past, where comment lines began with the letter C in the first column. I can't remember when (or if it ever) became valid to have completely blank lines in code. However, blank lines, or lines beginning with C, or with !, are very useful. Divide your code up into logical blocks. Sometimes just white space around a block of code is enough to make it more readable even with no comments.

Use sensible names for variables. If you like to program in Mixed Case, then this helps. The underscore character helps too. For example:

NoOfElements or No_of_elements are far more meaningfull than NELES - although even that is better than NE ... now we can have long names the code becomes far more readable. However, beware. Sometimes very long names just irritate you when you have to type them. Also avoid stupid unhelpful comments, such as:

NELES=0 ! set NELES to zero.

When I leartn Fortran first, it was programmed in capital letters. When we punched cards, and often had a limit on the number of cards we could have in a job, then comments were very few. The number of cards stopped being an issue about the time lower case letters were allowed. I still program code in capitals, and comments in lower case. If you have your own system, you will find it makes the comments stand out.

FTN95 has an excellent debugger. The instructions on how to use it are in FTN95.CHM, and the manuals available in the Documentation section of this website - some of it going back to when the compiler was FTN77 not 95. There is no substitute for having a go, and seeing where you come up with a problem. No doubt someone will help through this forum if you have a specific problem - general queries are much more difficult to answer.

Eddie

[sparge]

As regards question 1, that is a question about programming environment not the FORTRAN 90 programming language. (Unless you meant "Is there a way within the language to indicate that all the lines between <here> and <here> are to be parsed as consecutive comment lines - in which case, the answer is no).

Presumably since you are here, you are using Salford software, so if you are also using the Plato IDE for your programming, there is a menu item (fairly unintuitively hidden) ... select a bunch of lines then choose Edit-Advanced-Comment Selection to comment all of them. Not much quicker than adding ! to each line manually unless its a big bunch, though

Andy

[JohnCampbell]

[IanLambley]

John's comments regarding common / module are correct. As an oldie, I understand the common block approach better and you can do such sneaky things - it is a bit more raw, but modules are perhaps the way forward, keeping common blocks in reserve for the lower level fiddles which may prove necessary.

Keeping subroutines and functions short it also good, but I must admit that I have a few!!! which do not comply with John's excellent recommendations. Short routines are helped by use of the "include" or "use" statements.

Ian