Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!tektronix!tekcrl!tekgvs!toma
From: toma@tekgvs.LABS.TEK.COM (Tom Almy)
Newsgroups: comp.sys.ibm.pc
Subject: Re: using files in C on the IBM PC
Message-ID: <5140@tekgvs.LABS.TEK.COM>
Date: 15 May 89 15:12:23 GMT
References: <110@sol.bucknell.edu> <1989May11.203209.9152@ziebmef.uucp>
Reply-To: toma@tekgvs.LABS.TEK.COM (Tom Almy)
Organization: Tektronix, Inc., Beaverton,  OR.
Lines: 36

In article <1989May11.203209.9152@ziebmef.uucp> stephen@ziebmef.UUCP (Stephen M. Dunn) writes:
>
>   Okay, most or all of the common C compilers for DOS operate in
>"cooked" mode by default on file accesses.  This means that they treat
>^Z (otherwise known as EOF) as the end-of-file marker, and they will
>play around with CRs and LFs.  There is another mode of file access
>known as "raw" mode to DOS people and "binary" mode to C people.  Instead
>of saying R or W as your file access mode, say RB or WB instead and
>DOS will stop playing with your file.  You can then read or write whatever
>character codes your heart desires without fear of intervention from
>DOS.

Actually there are two different features (?) being discussed here --
"raw" vs "cooked" and "ascii" vs "binary".  

"ascii" vs "binary" is an artifact of C's treatment of end of lines.  DOS
denotes end of lines with a CR LF pair, while C uses a single LF character.
When a file is opend "ascii" (usually the default, but can be forced by
opening "ra" or "wa" in most C libraries) CR's are stripped on input and
prepended to any LF's on output.  

"raw" vs "cooked" is a DOS driver feature (also in UNIX).  If, for instance,
the keyboard is "raw" control-C characters will always be passed to the
program rather than treated as special case interrupt character.  Also
display output speed is improved in RAW mode because the keyboard buffer
does not need to be checked, and certain drivers (such as NANSI.SYS or
FANSI-CONSOLE) can work more efficiently.  If you are doing graphics to a
printer, you need to set raw mode.  

I'm not sure if the various C library setmode() routines affect just 
"ascii" vs "binary" or also change "raw" vs "cooked".  I always issue
the DOS calls directly to set raw mode.

Tom Almy
toma@tekgvs.labs.tek.com
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