C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  size of a byte and int? Goto page 1, 2, 3, 4  Next          C++Talk.NET Forum Index -> C Language View previous topic :: View next topic   Author Message Neo Guest Posted: Tue Jan 25, 2005 7:41 am    Post subject: size of a byte and int? Hi All, Is that true that size of a byte not necessarily 8-bit? What the std. says? If that true, then what will the size of an int, i mean what sizeof(int) should return? On my machine sizeof(char) == sizeof(int). TMS320C5402 DSP (with 16-bit word size). both returns one. So, it holds true. But my interpretation is : Size of int,float etc is specified in terms of bytes, not bits...which is a standard i.e int -> 2 bytes, char -> 1 byte etc... now, actual size of these depends up on no. of bits in a byte... which is implementation defined. So, if we say on a machine its defined 1 byte = 8 bits then size(char) = 1byte = 8 bits size(int) = 2 bytes = 16 bits... but on other machine 1 byte = 16 bits the size(char) = 1byte = 16 bits and Size(Int) =2 bytes= 32 bits. In no case, it can be same for both char & int. Please help me where I am missing. -Neo Back to top pete Guest Posted: Tue Jan 25, 2005 7:58 am    Post subject: Re: size of a byte and int? Neo wrote: Quote: Hi All, Is that true that size of a byte not necessarily 8-bit? Width is measured in bits. Size is measured in bytes. -- pete Back to top Neo Guest Posted: Tue Jan 25, 2005 8:11 am    Post subject: Re: size of a byte and int? "pete" <pfiland (AT) mindspring (DOT) com> wrote Quote: Neo wrote: Hi All, Is that true that size of a byte not necessarily 8-bit? Width is measured in bits. Size is measured in bytes. -- pete O'kay! What does int and char (data types in C) are measured in? -Neo Back to top Peter Nilsson Guest Posted: Tue Jan 25, 2005 8:23 am    Post subject: Re: size of a byte and int? Neo wrote: Quote: Is that true that size of a byte not necessarily 8-bit? Yes. Quote: What the std. says? It says that a byte is CHAR_BIT bits in width, where CHAR_BIT >= 8. Quote: If that true, then what will the size of an int, i mean what sizeof(int) should return? It will be whatever it is on a given implementation. Quote: On my machine sizeof(char) == sizeof(int). TMS320C5402 DSP (with 16-bit word size). both returns one. So, it holds true. But my interpretation is : Size of int,float etc is specified in terms of bytes, not bits... No. Integers and floats are specified in terms of value limits and precision. The minimum range that a signed int must be able to represent is -32767..32767. Mathematics dictate that this requires at least 16 bits (including a sign bit.) Thus, an int will require _at least_ as many bytes as is required to store 16-bits. Quote: Please help me where I am missing. Google for N869 and read the last public draft of the C99 standard. -- Peter Back to top infobahn Guest Posted: Tue Jan 25, 2005 9:21 am    Post subject: Re: size of a byte and int? Neo wrote: Quote: "pete" <pfiland (AT) mindspring (DOT) com> wrote in message news:41F5FC17.1161 (AT) mindspring (DOT) com... Neo wrote: Hi All, Is that true that size of a byte not necessarily 8-bit? Width is measured in bits. Size is measured in bytes. -- pete O'kay! What does int and char (data types in C) are measured in? Bytes or bits, depending on whether you want size or width. sizeof(char) is 1, by definition. A char comprises CHAR_BIT bits. CHAR_BIT is defined in <limits.h> and its value can vary from one implementation to the next, but it can be no lower than 8. sizeof(int) is at least 16 bits wide. Therefore, it must be at least (16 + CHAR_BIT - 1) / CHAR_BIT bytes in size (ignoring any remainder). int must be able to represent all values in the range -32767 to +32767. Back to top 42Bastian Schick Guest Posted: Tue Jan 25, 2005 9:25 am    Post subject: Re: size of a byte and int? Quote: Bytes or bits, depending on whether you want size or width. sizeof(char) is 1, by definition. Could be 2 on some DSPs (IIRC TI's). -- 42Bastian Do not email to [email]bastian42 (AT) yahoo (DOT) com[/email], it's a spam-only account Use <same-name>@monlynx.de instead ! Back to top 42Bastian Schick Guest Posted: Tue Jan 25, 2005 9:31 am    Post subject: Re: size of a byte and int? On Tue, 25 Jan 2005 13:11:04 +0530, "Neo" <timeless_illusion (AT) yahoo (DOT) com> wrote: Quote: Hi All, Is that true that size of a byte not necessarily 8-bit? I think common sense is that a byte is nowadays 8 bit. Quote: What the std. says? If that true, then what will the size of an int, Don't mix byte with char ! I don't think there is a std defining the width of a byte. Quote: i mean what sizeof(int) should return? On my machine sizeof(char) == sizeof(int). TMS320C5402 DSP (with 16-bit word size). ^^^ That's it, they speak of words avoiding the term byte. A reason, to define __u8,__u16,__u32 etc. (or the like) depending on the cpu and/or compiler. -- 42Bastian Do not email to [email]bastian42 (AT) yahoo (DOT) com[/email], it's a spam-only account Use <same-name>@monlynx.de instead ! Back to top Paul Black Guest Posted: Tue Jan 25, 2005 9:36 am    Post subject: Re: size of a byte and int? 42Bastian Schick wrote: Quote: Bytes or bits, depending on whether you want size or width. sizeof(char) is 1, by definition. Could be 2 on some DSPs (IIRC TI's). No, it can't. By _definition_, sizeof(chat) is 1. This is stated in the C standard. -- Paul Black mailto:paul.black (AT) oxsemi (DOT) com Oxford Semiconductor Ltd http://www.oxsemi.com 25 Milton Park, Abingdon, Tel: +44 (0) 1235 824 909 Oxfordshire. OX14 4SH Fax: +44 (0) 1235 821 141 Back to top Peter Nilsson Guest Posted: Tue Jan 25, 2005 9:50 am    Post subject: Re: size of a byte and int? 42Bastian Schick wrote: Quote: "Neo" Hi All, Is that true that size of a byte not necessarily 8-bit? I think common sense is that a byte is nowadays 8 bit. Sense, common to what? An 8-bit entity is called an 'octet' explicitly by many standards and protocols, precisely to avoid confusion. Quote: What the std. says? If that true, then what will the size of an int, Don't mix byte with char ! I don't think there is a std defining the width of a byte. The standard does define that a byte has an implementation width which is big enough to hold the representation of a character from the basic character set. The standard also states that the size of all three character types is 1 byte. Quote: i mean what sizeof(int) should return? On my machine sizeof(char) == sizeof(int). TMS320C5402 DSP (with 16-bit word size). ^^^ That's it, they speak of words avoiding the term byte. Who is 'they'? A C programmer will still speak of bytes. Quote: A reason, to define __u8,__u16,__u32 etc. (or the like) depending on the cpu and/or compiler. Programs targetting hosted implementations will generally have little need for such types. Indeed, implementations on certain architectures may not be able to represent such precise width types, outside of inefficient emulation. C99 introduced the intN_t types to cater for programs which do rely on precise width twos complement integer types, however programs which make use of them are not strictly conforming. -- Peter Back to top Neo Guest Posted: Tue Jan 25, 2005 10:38 am    Post subject: Re: size of a byte and int? "Peter Nilsson" <airia (AT) acay (DOT) com.au> wrote Quote: 42Bastian Schick wrote: [-snip-] C99 introduced the intN_t types to cater for programs which do rely on precise width twos complement integer types, however programs which make use of them are not strictly conforming. -- Peter Why not conforming? Then why does the std. defines these? -Neo Back to top Thomas Stegen Guest Posted: Tue Jan 25, 2005 10:46 am    Post subject: Re: size of a byte and int? Neo wrote: Quote: "Peter Nilsson" <airia (AT) acay (DOT) com.au> wrote in message news:1106646608.010225.80650 (AT) z14g2000cwz (DOT) googlegroups.com... C99 introduced the intN_t types to cater for programs which do rely on precise width twos complement integer types, however programs which make use of them are not strictly conforming. -- Peter Why not conforming? (They are not _strictly_ conforming) Because a platform is not required to provide them. Just in case it cannot support them. Quote: Then why does the std. defines these? Probably to make the interface to this functionality uniform across the subset of platforms that can support them. This is not a bad thing since code that really needs this is unlikely to ever have much use on a platform which cannot provide this. -- Thomas. Back to top David Guest Posted: Tue Jan 25, 2005 10:55 am    Post subject: Re: size of a byte and int? On Tue, 25 Jan 2005 09:25:50 +0000, 42Bastian Schick wrote: Quote: Bytes or bits, depending on whether you want size or width. sizeof(char) is 1, by definition. Could be 2 on some DSPs (IIRC TI's). No, sizeof(char) is 1 even on DSP's that cannot access smaller than 16-bit data. In the case of the TMS320F24x, sizeof(char) = sizeof(int), with both being 16-bit. Makes the chip a real pain. Back to top Hans-Bernhard Broeker Guest Posted: Tue Jan 25, 2005 1:45 pm    Post subject: Re: size of a byte and int? [F'up2 cut down --- should have been done by OP!] In comp.arch.embedded Neo <timeless_illusion (AT) yahoo (DOT) com> wrote: Quote: Is that true that size of a byte not necessarily 8-bit? What the std. says? If that true, then what will the size of an int, i mean what sizeof(int) should return? You cross-posted this question to two newsgroups, one of which (c.a.e) it is seriously off-topic in. Please don't do that, or if you do, at least explain why, and set a Followup-To. As is, your posting silently assumes a context that only applies to half your audience, causing all kinds of needless confusion. In the context of comp.arch.embedded, your question doesn't make much sense at all. In the context of comp.lang.c, the answers to the above are: Yes. The same. Implementation-defined. (In that order). Your confusion seems to come from the fact that you don't realize that sizeof(int), too, is implementation-defined (within limitations set up by the standard on the range of values an int must at least be able to hold). In theory, an implementation could have, say CHAR_BITS == 13 sizeof(short) == 2 sizeof(int) == 3 sizeof(long) == 5 sizeof(float) == 7 sizeof(double) == 9 just for the perverse fun of it. -- Hans-Bernhard Broeker (broeker (AT) physik (DOT) rwth-aachen.de) Even if all the snow were burnt, ashes would remain. Back to top Neo Guest Posted: Tue Jan 25, 2005 2:17 pm    Post subject: Re: size of a byte and int? "Hans-Bernhard Broeker" <broeker (AT) physik (DOT) rwth-aachen.de> wrote Quote: [F'up2 cut down --- should have been done by OP!] In comp.arch.embedded Neo <timeless_illusion (AT) yahoo (DOT) com> wrote: Is that true that size of a byte not necessarily 8-bit? What the std. says? If that true, then what will the size of an int, i mean what sizeof(int) should return? You cross-posted this question to two newsgroups, one of which (c.a.e) it is seriously off-topic in. Please don't do that, or if you do, at least explain why, and set a Followup-To. As is, your posting silently assumes a context that only applies to half your audience, causing all kinds of needless confusion. In the context of comp.arch.embedded, your question doesn't make much sense at all. In the context of comp.lang.c, the answers to the above are: Yes. The same. Implementation-defined. (In that order). Your confusion seems to come from the fact that you don't realize that sizeof(int), too, is implementation-defined (within limitations set up by the standard on the range of values an int must at least be able to hold). In theory, an implementation could have, say CHAR_BITS == 13 sizeof(short) == 2 sizeof(int) == 3 Shouldn't sizeof(int) be 2 here? As per the post by infobart : sizeof(int) is at least 16 bits wide. Therefore, it must be at least (16 + CHAR_BIT - 1) / CHAR_BIT bytes in size (ignoring any remainder). int must be able to represent all values in the range -32767 to +32767. 2 bytes here consisting of 26 bits can represent all these values so, it should be 2 why 3 then? -Neo Quote: sizeof(long) == 5 sizeof(float) == 7 sizeof(double) == 9 just for the perverse fun of it. -- Hans-Bernhard Broeker (broeker (AT) physik (DOT) rwth-aachen.de) Even if all the snow were burnt, ashes would remain. Back to top Ignacio G. T. Guest Posted: Tue Jan 25, 2005 2:31 pm    Post subject: Re: size of a byte and int? David wrote: Quote: On Tue, 25 Jan 2005 09:25:50 +0000, 42Bastian Schick wrote: Bytes or bits, depending on whether you want size or width. sizeof(char) is 1, by definition. Could be 2 on some DSPs (IIRC TI's). No, sizeof(char) is 1 even on DSP's that cannot access smaller than 16-bit data. In the case of the TMS320F24x, sizeof(char) = sizeof(int), with both being 16-bit. Makes the chip a real pain. Mmm... yes, but, beware: sizeof(char) = 1; sizeof('c') = 1; // In C++ sizeof('c') = sizeof(int); /* In C */ Back to top        C++Talk.NET Forum Index -> C Language All times are GMT Goto page 1, 2, 3, 4  Next Page 1 of 4 Powered by phpBB © 2001, 2006 phpBB Group