ansi types

[Bill Cunningham]

I am using in my code an unsigned char when I could be using a char.
Just what does the standard say about all these types? On my machine a long
and long long are not the same. However char and unsigned char are the same
in length of bit streams that it. Double is 8 bytes and int is 4 just like
char. Does C treat these data types as different in any way other than
length? Could I not say,

int *i="stream\n"; rather than
char *p="stream\n";
And not lose lose anything of value other than having strange looking code?

Bill

 

[Bill Cunningham]

Bill Cunningham said:
[snip]

Double is 8
bytes and int is 4 just like
char.

char can't be 4 bytes. It has to be 1 byte, by definition (where one
byte consists of exactly CHAR_BIT bits, defined in <limits.h>).

Oops. I meant int is 4 bytes. char is 1. Now is char an unsigned or
signed char by default? My machine also says size_t is 4 bytes. What the
standard says a return type is is I guess what it is. Example, int getc. But
I have discovered so many people using all these types in their code. Is a
long of type int? Then there's short of course. I am asking all of this for
portability and understand more about types to not use too much space or too
little.

Bill

 

[Bill Cunningham]

The current Standard (incorporating three Technical

Corrigenda) may be downloaded from
http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf

Wow thanks for the link. Now I can actually read the standard instead of
hearing others talk about it.

Bill

 

[Bill Cunningham]

char, signed char, and unsigned char are three distinct types,
even though two of them (char and one of the other two) have the
same representation. Use whichever one makes sense in a particular
context; char for character data, unsigned char for byte data,
and signed char when you want a very narrow signed integer (the
latter is relatively rare).

What is narrow signed" ?

Bill

 

[Tom St Denis]

 The current Standard (incorporating three Technical


Wow thanks for the link. Now I can actually read the standard instead of
hearing others talk about it.

Bill

I have a simpler link for the folks here to remember

http://tinyurl.com/mnhtx2

[work safe]

Tom

 

[Keith Thompson]

Bill Cunningham said:



It depends on the implementation. But if you use char for text data,
unsigned char for bytes of arbitrary provenance, then it will never
matter to you.

char, signed char, and unsigned char are three distinct types,
even though two of them (char and one of the other two) have the
same representation. Use whichever one makes sense in a particular
context; char for character data, unsigned char for byte data,
and signed char when you want a very narrow signed integer (the
latter is relatively rare).

It's of type long int.


Which is of type short int.

To be clear, "long int" and "long" are two different names for the
same type; similarly, "short int" and "short" are two different names
for the same type. (Saying that short is of type short int might
obscure that point.)

short int, int, long int, and long long int are four distinct types,
even though some or all of them may have the same representation.

[snip]

 

[Phil Carmody]

Bill Cunningham said:



It depends on the implementation. But if you use char for text data,
unsigned char for bytes of arbitrary provenance, then it will never
matter to you.

I thought that its signedness depended on the implementation, but
that it was a third type distinct from either signed or unsigned
char, simply coincident in properties with one of the other two.

Phil

 

[Keith Thompson]

I thought that its signedness depended on the implementation, but
that it was a third type distinct from either signed or unsigned
char, simply coincident in properties with one of the other two.

Correct.

 

[Phil Carmody]

Correct.

Blimey - you're quick - I was just about to cancel my message as
I spotted it was completely redundant after yours!

Phil

 

[Keith Thompson]

What is narrow signed" ?

There's no particular meaning for the phrase "narrow signed".
I merely meant a signed type that is narrow (i.e., covers a small
range and doesn't occupy much memory).

 

[Antoninus Twink]

Now is char an unsigned or signed char by default?

On your platform, and any platform your code is ever likely to run on,
it's signed.

 

[Nick Keighley]

On 11 Aug 2009 at  0:59, Bill Cunningham wrote:

On your platform, and any platform your code is ever likely to run on,
it's signed.

but it's easy to write code that doesn't depend on this.
So why do otherwise?