char label[8] = "abcdefgh";
char arr[7] = "abcdefg";
printf("%s\n",label);
printf("%s",arr);
====output==========
abcdefgh
abcdefgÅ
Why Å is appended at the end of the string arr? I am running C code in Turbo C ++.
views:
179answers:
4
+14
A:
printf expects NUL-terminated strings. Increase the size of your char arrays by one to make space for the terminating NUL character (it is added automatically by the = "..." initializer).
If you don't NUL-terminate your strings, printf will keep reading until it finds a NUL character, so you will get a more or less random result.
Heinzi
2009-11-02 06:43:14
Here's a tutorial on the theory behind this: http://www.cplusplus.com/doc/tutorial/ntcs/
Heinzi
2009-11-02 06:44:25
Or, you could use empty brackets, e.g. 'char label[]', to allow the compiler to correctly size the arrays for you.
Paul Baker
2009-11-02 06:48:15
Or drop the explicit sizes and let the compiler do the counting; computers are good at counting!
Jonathan Leffler
2009-11-02 06:48:56
But why it is showing output "abcdefgh" when giving array length 8 and assigning "abcdefgh" to the char array label? the difference between arr and label is that I have set the length 7 and assigned "abcdefg" to arr and the length 8 and assigned "abcdefgh" to label. both are similar respect to length(7,8) and no. of characters(7,8)?
Himadri
2009-11-02 08:10:30
It's a conincidence that it works. Apparently, in memory right behind array label, there is a NUL character, so printf stops. See Amits answer for what it could look like on a different machine.
Heinzi
2009-11-02 08:28:39
+4
A:
Your string is not null terminated, so printf is running into junk data. You need to use the '\0' at the end of the string.
Myles
2009-11-02 06:44:15
+2
A:
Using GCC (on Linux), it prints more garbage:
abcdefgh°ÃÕÄÕ¿UTÞÄÕ¿UTÞ·
abcdefgabcdefgh°ÃÕÄÕ¿UTÞÄÕ¿UTÞ·
This is because, you are printing two character arrays as strings (using %s).
This works fine:
char label[9] = "abcdefgh\0"; char arr[8] = "abcdefg\0";
printf("%s\n",label); printf("%s",arr);
However, you need not mention the "\0" explicitly. Just make sure the array size is large enough, i.e 1 more than the number of characters in your strings.
Amit
2009-11-02 06:46:59
+5
A:
Your variables label and arr are not strings. They are arrays of characters.
To be strings (and for you to be able to pass them to functions declared in <string.h>) they need a NUL terminator in the space reserved for them.
Definition of "string" from the Standard
7.1.1 Definitions of terms
1 A string is a contiguous sequence of characters terminated by and including
the first null character. The term multibyte string is sometimes used
instead to emphasize special processing given to multibyte characters
contained in the string or to avoid confusion with a wide string. A pointer
to a string is a pointer to its initial (lowest addressed) character. The
length of a string is the number of bytes preceding the null character and
the value of a string is the sequence of the values of the contained
characters, in order.
pmg
2009-11-02 07:48:11