sizeof() with strings

mscoder · 06-06-2012, 02:31 PM

What would be the output of the following program?...it comes out as 5...i cant understand the reason..

...isnt the name of array treated as a pointer??..even if not,why doesnt the caluculated size include that for the terminating null character?

Code:

#include <stdio.h>
main()
{
char str[]="S65AB";
printf("\n%d", sizeof(str));
}

d3adc0de · 06-06-2012, 02:40 PM

This function counts how many characters are in the string, and outputs the result.

Code:

#include <stdio.h>
main()
{
char str[]="S65AB"; #The string which you're counting how many characters it has (which is 5 characters)
printf("\n%d", sizeof(str)); #The printed out result (on your screen not to your printer) of the function.
}

The sizeof operator is built into many programming languages including PHP and C, C++

mscoder · 06-06-2012, 02:48 PM

## d3adc0de...i know the use of sizeof() operato.i meant to clarify that why wasnt the name of array (str in this case) treated as a pointer as it always is...n that the o/p(on my screen..not my printer) should have been 6 even if size was calculated due to the null character at the end of array..

Nominal Animal · 06-06-2012, 02:55 PM

Quote:

Originally Posted by mscoder

What would be the output of the following program?

After fixing the obvious bugs, 6.

Quote:

Originally Posted by mscoder

...it comes out as 5...i cant understand the reason..

Any standards-compliant compiler will output 6. If your compiler produces code that outputs 5, then it observes that str is not used as a string anywhere, and instead treats the declaration of the array as if it was written as char str[5] = { 83, 54, 53, 65, 66 }; . You can make sure the compiler does not do that optimization by referring to str as a string, for example by printing it.

Quote:

Originally Posted by d3adc0de

This function counts how many characters are in the string, and outputs the result.

That is utterly false. First, sizeof is not a function, it is an operator. Second, it yields the size of the type referred to, not the size allocated. When applied to a character array (which strings are in C), it yields the size of the array, not the string length.

You must be confusing sizeof and strlen().