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From: Slomcenski.WBST@Xerox.COM
Newsgroups: comp.lang.pascal
Subject: Re: TURBO Pascal READ
Message-ID: <7083@brl-adm.ARPA>
Date: Fri, 24-Apr-87 08:40:23 EST
Article-I.D.: brl-adm.7083
Posted: Fri Apr 24 08:40:23 1987
Date-Received: Sat, 25-Apr-87 09:06:16 EST
Sender: news@brl-adm.ARPA
Lines: 47

>
>  I noticed similar behavior and wrote about it to info-ibmpc
>last summer. MS-DOS screws up buffering input into pascal
>programs (turbo-pascal) at least. I wrote a simple program
>
>program test(input,output);
>
>var ch:char;
>
>begin
>writeln('enter character');
>read(ch);
>writeln(ch);
>end.
>
>If you compile and run this with Turbo (com option)
>and respond with a string say "abc", then the
>program will run correctly the first time, echoing an a. The second time
>you run it it will ignore you're input, whatever that may be and
>echo a 'b'. This will go on until the string 'abc' including cr and lf
>are consumed. I should back off a little. I havent tried it
>since last summer and turbo and/or MS-DOS might have been fixed
>since then but it drove me nuts then. The moral of this story

In fact TURBO and/or MS-DOS aren't broke in this case! I believe that what
you are seeing is the fact that MS-DOS "remembers" up to 16 characters
typed at the keyboard in its internal type-ahead buffer. To guarantee that
one and only one char is read by the program, the internal type-ahead buffer
should be flushed by either an MS-DOS call (facilities to flush any remaining
keys is provided by MS-DOS), or by TURBO code like:

  while keypressed do read(ch);

The following should do what you expect it to:

program test(input,output);

var ch:char;

begin
while keypressed do read(ch); (* flush any old chars in kbd buffer *)
writeln('enter character');
read(ch);
writeln(ch);
end.

  ~Bob