One of the more obscure error messages you can get at run time is Access Violation, which the Visual Fortran run-time library reports as error number 157. The documentation says that it is a “system error,” meaning that it is detected by the operating system, but many users think they’re being told that their system itself has a problem. In this article, I’ll explain what an access violation is, what programming mistakes can cause it to occur, and how to resolve them.
MoreDoctor Fortran in “To .EQV. or to .NEQV., that is the question”, or “It’s only LOGICAL”
Most Fortran programmers are familiar with the LOGICAL data type, or at least they think they are…. An object of type LOGICAL has one of only two values, true or false. The language also defines two LOGICAL constant literals .TRUE. and .FALSE., which have the values true and false, respectively. It seems so simple, doesn’t it? Yes… and no.
Doctor Fortran and “The Dog that Did Not Bark”
In past issues of the newsletter, Dr. Fortran has discussed an assortment of things, sometimes obscure, that the Fortran standard says. In this issue, he’s going to take a page from Sherlock Holmes and talk about things that the standard doesn’t say, and how they can bite you as well.
MoreDoctor Fortran says “Better SAVE Than Sorry”
In this issue, Dr. Fortran takes on another less-understood feature of the Fortran language, the SAVE attribute.
Back in the “good old days” of Fortran programming, when lowercase letters hadn’t been invented yet and we strung our core memory wires by hand, programmers knew that local variables lived in fixed memory locations and, of course, took advantage of that, writing code such as this:
MoreHey! Who are you calling “obsolescent”?
Steve Lionel, DVF Development Team
Dr. Fortran didn’t receive any appropriate questions for his column this time, so he’s going to take on a topic that is sure to raise a ruckus each time it is brought up in the comp.lang.fortran newsgroup: Obsolescent and Deleted Features.
MoreAsk Dr. Fortran
Dear Dr. Fortran,
I know this program who seems to be OK, but he is a little different from all the other programs. (Just between you and me, he is a legacy program. Don’t let that get out. It would not be politically correct.)
He started out life written for the IBM 1130 Disk Monitor System with 8k of core storage. He was written in 1130 FORTRAN. The original documentation gives direction as to which switches on the computer must be flipped to invoke certain options. But he is still alive and works well. We still add things to him. He lives on PCs now.
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