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READ* causes run-time error after file has been opened/close

 
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viroxa



Joined: 28 Jul 2017
Posts: 77

PostPosted: Mon Aug 14, 2017 4:08 pm    Post subject: READ* causes run-time error after file has been opened/close Reply with quote

Hello, everyone,

I opened a file using
Code:
OPEN(UNIT=1,FILE='...',STATUS='old',IOSTAT=stats)


after reading data from that file, I closed it again, using
Code:
CLOSE(UNIT=1)


After that, READ* - which should get user input from the command promt returns
Quote:
"Run-time error 94: Unit has neither been OPENed nor preconnected"


PRINT*,'...' on the other hand, works just fine.

How can I open the command prompt for input again?[/quote]
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LitusSaxonicum



Joined: 23 Aug 2005
Posts: 1683
Location: Yateley, Hants, UK

PostPosted: Mon Aug 14, 2017 4:31 pm    Post subject: Reply with quote

I think that it is advisable not to use low-numbered units in an OPEN statement, as the idea is that they are 'pre-connected'. Old-fashioned advice was to avoid units 5 and 6, because traditionally they were the card reader (5) and line-printer (6). On the first machine I ever used, 1 was the operator's console, 2 and 3 were tape readers, and 4 was the tape punch. 7 was another card reader!

If you are using a pre-connected unit, never CLOSE it, or you are likely to get the problems you describe. A unit number given as * is also pre-connected. If a UNIT is pre-connected, you do not need to OPEN it.

The advice given in FTN95.CHM is: "UNIT values should be greater than 6 to avoid the possibility of re-assigning standard input/output streams."

Eddie
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viroxa



Joined: 28 Jul 2017
Posts: 77

PostPosted: Mon Aug 14, 2017 5:17 pm    Post subject: Reply with quote

Thanks for the detailed explanation!

I'm working with code that someone had written back in the 90's. They only excluded 5 and 6.
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