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From: dennison@romulus23.DAB.GE.COM (Ted Dennison)
Newsgroups: comp.lang.ada
Subject: Re: Ada replacements for DOS I/O
Date: 28 Oct 1994 12:17:34 GMT
Organization: General Electric SCSD, Daytona Beach FL
Sender: dennison@romulus23 (Ted Dennison)
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References: <44279.cwarwick@fox.nstn.ns.ca>
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Date: 1994-10-28T12:17:34+00:00
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In article <44279.cwarwick@fox.nstn.ns.ca>, "Elgar the Idiot aka Chris Warwick" <cwarwick@fox.nstn.ns.ca> writes:
|> We just got burned on a project using Alsys Ada. Seems we had assumed that 
|> a multi-tasking Ada program would perform I/O is parallel with other 
|> processing. The system service call actucally halts all processing in the 
|> program until the system service is complete...
|> 
|> I don't mean to burn Alsys, since the bug(?) also exists in the Verdix 
|> compiler we are using. The difference is the Verdix is for Unix so we just 
|> sidestepped the problem by not using Ada tasks...
|> 
|> Does anyone know of any replacements for the DOS I/O (specifically the Disk 
|> I/O operations) compatable with Alsys Ada?
|>  --
|>  Lorne Elliot in a Conan the Barabarian suit, or
|>  "Beware the fool, for only the fool may speak the truth"
|> 
|>  Chris Warwick
|>  cwarwick@fox.nstn.ns.ca
|>  warwick@anchor.hfx.prior.ca

Don't be so hard on Alsys (at least not for this). I know of NO Ada system
on any platform that handles tasks and I/O that well. VAX Ada comes close, 
but simultanious Text_IOs will kill the application. Tasks and I/O are 
NEVER a no-brainer.

There are several issues with tasking that can burn you. Your only real
protection is to investigate how these things work BEFORE you start coding.

As to your current problem, you will have to use low-level OS I/O calls that
do not block waiting for completion. If your OS (MeSsy-DOS?) does not have 
them, get another OS and/or platform, or live with it.

T.E.D.