Message-ID: <39322CCB.ABE07D4F@earthlink.net> From: Martin Ambuhl Organization: Nocturnal Aviation X-Mailer: Mozilla 4.73 [en] (Win95; U) X-Accept-Language: en MIME-Version: 1.0 Newsgroups: comp.os.msdos.djgpp Subject: Re: advance in allocated memory by 1 byte only References: <01BFC967 DOT 2C9F11E0 AT LEON DOT caresystems DOT com DOT au> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 36 Date: Mon, 29 May 2000 08:38:49 GMT NNTP-Posting-Host: 63.23.136.58 X-Complaints-To: abuse AT earthlink DOT net X-Trace: newsread1.prod.itd.earthlink.net 959589529 63.23.136.58 (Mon, 29 May 2000 01:38:49 PDT) NNTP-Posting-Date: Mon, 29 May 2000 01:38:49 PDT To: djgpp AT delorie DOT com DJ-Gateway: from newsgroup comp.os.msdos.djgpp Reply-To: djgpp AT delorie DOT com Leon wrote: > > Hello > i know one can use pointer arithmetic to advance the read/write location in memory allocated by malloc for example... > > Now since the sizeof char is 1 byte - it is possible to use a pointer to char when moving 1 byte at a time. > > but what about systems that may have different sizeof char (ie != 1 byte) There is no such thing. sizeof(char) == 1 by definition. Your confusion probably comes from not understanding that "byte" has a long history without any reference to a fixed number of bits. A byte (or char) may or may not be an octet (8 bits). It has been common for, as an example, a byte to be 9-bits on many 36-bit machines, where a char would also be 9 bits. There is an important family of machines, the PDP-6/10/20 family, on which byte pointers manipulation instructions were part of the machine instruction set and a byte was any aggregate of 1-36 bits not crossing word boundaries. A C implementation would need to use just one of the sizes in the range 8-36 and stick to it, but the implementors would have the freedom to choose (the natural choice to maintain arithmetic types close to the machine being 9- or 18-bits). > > how would one then be able to move through a memory block by 1 byte only? > > With best regards - Leon. -- Martin Ambuhl mambuhl AT earthlink DOT net What one knows is, in youth, of little moment; they know enough who know how to learn. - Henry Adams A thick skin is a gift from God. - Konrad Adenauer