why?

[xcm]

#include<stdio.h>
main()
{ printf("%d %d\n",sizeof('a'),sizeof('A'));}

why does it printf 2 2 in tc.

 

[pete]

#include<stdio.h>
main()
{ printf("%d %d\n",sizeof('a'),sizeof('A'));}

why does it printf 2 2 in tc.

My guess is that sizeof(int) equals 2 in tc.

 

[pete]

My guess is that sizeof(int) equals 2 in tc.

A more better way of writing it would be

#include <stdio.h>

int main(void)
{
printf("%u %u\n", (unsigned)sizeof('a'), (unsigned)sizeof('A'));
return 0;
}

 

[john_bode]

#include<stdio.h>
main()
{ printf("%d %d\n",sizeof('a'),sizeof('A'));}

why does it printf 2 2 in tc.

Character constants are typed int, not char (confusing, I know). So
sizeof('a') is equivalent to sizeof(int).

 

[James McIninch]

<posted & mailed>

sizeof() returns the size of the type of the data specified as the argument.
Here, you've specified an integer ('a' and 'A'), so, the size is whatever
the size of integer is on your system (apparently 2).

 

[xcm]

is 'a' an integer when use the sizeof?
why?
the result is 1 in vc but 2 in tc.
why dose the compiler assume that 'a' is not a char but an integer
thanks for the reply;

 

[Paul Mesken]

A more better way of writing it would be

#include <stdio.h>

int main(void)
{
printf("%u %u\n", (unsigned)sizeof('a'), (unsigned)sizeof('A'));
return 0;
}

Why the cast? size_t is unsigned (see 7.1.6 of the Standard).

 

[Paul Mesken]

is 'a' an integer when use the sizeof?
why?
the result is 1 in vc but 2 in tc.
why dose the compiler assume that 'a' is not a char but an integer

Ah, this is a difference between using C++ and C. If sizeof('a')
equals 1 then you're using a C++ compiler, if it equals something
greater than 1 (when it returns the same value for sizeof(int)) then
you're using a C compiler.

You see :

In C character literals (like 'a') have sizeof(int).
In C++ character literals have sizeof(char).

 

[Al Bowers]

is 'a' an integer when use the sizeof?
why?
the result is 1 in vc but 2 in tc.
why dose the compiler assume that 'a' is not a char but an integer
thanks for the reply;

You should consult the clc faq especially question 8.9
http://www.eskimo.com/~scs/C-faq/q8.9.html

 

[xcm]

"Al Bowers"

thank you every much

 

[Emmanuel Delahaye]

xcm wrote on 29/05/05 :

#include<stdio.h>
main()
{ printf("%d %d\n",sizeof('a'),sizeof('A'));}

Your code is incorrect because the type returned byte sizeof is size_t.
Nota that the parens after sizeof are only mantadory with a type.

C90 (paranoid portability):

printf ("%lu %lu\n", (unsigned long) sizeof 'a', (unsigned long)
sizeof 'A');

C90 (sensible mode):

printf ("%u %u\n", (unsigned) sizeof 'a', (unsigned) sizeof 'A');

C99:

printf ("%zu %zu\n", sizeof 'a', sizeof 'A');

why does it printf 2 2 in tc.

Because
- in C, a character literal has the type int
- Turbo C's CHAR_BIT is 8 and its INT_MAX is 32767 (see <limits.h>),
hence an int uses 16 bits that needs 2 char.

--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

I once asked an expert COBOL programmer, how to
declare local variables in COBOL, the reply was:
"what is a local variable?"

 

[Emmanuel Delahaye]

Paul Mesken wrote on 29/05/05 :

Why the cast? size_t is unsigned (see 7.1.6 of the Standard).

Nope. size_t is defined as an "unsigned integer" (according to the
target, could be an unsigned {char|short|int|long}).

unsigned integer != unsigned int.

--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

I once asked an expert COBOL programmer, how to
declare local variables in COBOL, the reply was:
"what is a local variable?"

 

[Emmanuel Delahaye]

xcm wrote on 29/05/05 :

is 'a' an integer when use the sizeof?
why?

'a' is always an integer with type int in C. It's written on the
standard. Don't ask why.

the result is 1 in vc but 2 in tc.

If the result is 1, you are probably using a C++ compiler. Check your
extension. Should be .c and neither .cpp nor .C.

In C++ a character literal has the type char. Once again, don't ask
why.

--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

..sig under repair

 

[Emmanuel Delahaye]

Paul Mesken wrote on 29/05/05 :

Ah, this is a difference between using C++ and C. If sizeof('a')
equals 1 then you're using a C++ compiler, if it equals something
greater than 1 (when it returns the same value for sizeof(int)) then

Bzzt. "greater or equal".

--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

"Clearly your code does not meet the original spec."
"You are sentenced to 30 lashes with a wet noodle."
-- Jerry Coffin in a.l.c.c++

 

[CBFalconer]

is 'a' an integer when use the sizeof?
why?
the result is 1 in vc but 2 in tc.
why dose the compiler assume that 'a' is not a char but an integer

VC is wrong, or is not being used as a C compiler. 'a' is not a
char, but an integer constant. It's so because that is what the
standard specifies.

--
Some informative links:
http://www.geocities.com/nnqweb/
http://www.catb.org/~esr/faqs/smart-questions.html
http://www.caliburn.nl/topposting.html
http://www.netmeister.org/news/learn2quote.html

 

[Paul Mesken]

Paul Mesken wrote on 29/05/05 :

Bzzt. "greater or equal".

You're very right.

Int might be the same size as char on the system (which is _extremely_
rare). The Standard doesn't require int to be greater than char, only
that int can at least represent the values between -32767 and 32767
and char is at least 8 bits.

I'm just so locked into thinking of char as an 8 bit byte

 

[Paul Mesken]

Paul Mesken wrote on 29/05/05 :

Nope. size_t is defined as an "unsigned integer" (according to the
target, could be an unsigned {char|short|int|long}).

unsigned integer != unsigned int.

Yep, 7.1.6 : "... size_t which is the unsigned integral type of the
result of the sizeof operator...". Int is an integral type but so is
char, short and long.

I'm learning something new everyday

 

[Emmanuel Delahaye]

Paul Mesken wrote on 29/05/05 :

Int might be the same size as char on the system (which is _extremely_
rare).

Not that rare in DSP world...

--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

"There are 10 types of people in the world today;
those that understand binary, and those that dont."

 

[roberth+news]

| xcm wrote on 29/05/05 :
| > is 'a' an integer when use the sizeof?
| > why?
|
| 'a' is always an integer with type int in C. It's written on the
| standard. Don't ask why.

The standard allows for character literals with more than one character
also (like 'ab' or 'aaaa'). Don't ask why.

| > the result is 1 in vc but 2 in tc.
|
| If the result is 1, you are probably using a C++ compiler. Check your
| extension. Should be .c and neither .cpp nor .C.
|
| In C++ a character literal has the type char. Once again, don't ask
| why.

This is not entirely correct. The C++ standard also allows for
character literals with more than one character, and for these the type
is int. As in C such literals have an implementation defined value.
Once again, don't ask why.

 

[Robert Gamble]

| xcm wrote on 29/05/05 :
| > is 'a' an integer when use the sizeof?
| > why?
|
| 'a' is always an integer with type int in C. It's written on the
| standard. Don't ask why.

The standard allows for character literals with more than one character
also (like 'ab' or 'aaaa'). Don't ask why.

You mean character constants, there is no such thing as character
literals in C.

Rob Gamble