What does the symbol mean in a string-literal?
up vote
47
down vote
favorite
Consider following code:
char str = "Hello";
What is the length of str array, and with how much 0s it is ending?
c++ c string escaping string-literals
|
show 7 more comments
up vote
47
down vote
favorite
Consider following code:
char str = "Hello";
What is the length of str array, and with how much 0s it is ending?
c++ c string escaping string-literals
3
@CodyGray: Why have you removed the C++ tag? This has changed the correctness of some of the answers and subsequent comments?
– CB Bailey
Jan 17 '11 at 9:20
3
@CodyGray: C strings are still often used in C++. As for answers not being correct, that was my point; I downvoted an incorrect answer and you magically made it correct thus invalidating my downvote.
– CB Bailey
Jan 17 '11 at 9:27
2
@Charles Bailey I am mainly using C++, but of course I want to know is there any difference between C and C++ . That's why I add C++ tag.
– UmmaGumma
Jan 17 '11 at 9:38
2
@Ashot: Next time, please add that to your question. It's difficult to infer things like that from tags, and I'm really bad at reading people's minds. @Charles: Ultimately, I suppose, my aim was to reduce ambiguity. It seems you're arguing my side when you say the correctness of answers hinges on the tags in use. Like I said, feel free to rollback my edits if you disagree.
– Cody Gray♦
Jan 17 '11 at 9:41
3
@CodyGray: At one particular point in the cycle of edits an answer suggested that something likechar a[2] = "OK";
was OK. I immediately downvoted but as I was writing my comment I double checked the tags and noted that the question was now only about C.
– CB Bailey
Jan 17 '11 at 9:52
|
show 7 more comments
up vote
47
down vote
favorite
up vote
47
down vote
favorite
Consider following code:
char str = "Hello";
What is the length of str array, and with how much 0s it is ending?
c++ c string escaping string-literals
Consider following code:
char str = "Hello";
What is the length of str array, and with how much 0s it is ending?
c++ c string escaping string-literals
c++ c string escaping string-literals
edited Nov 10 at 18:53
Deduplicator
33.7k64787
33.7k64787
asked Jan 17 '11 at 9:02
UmmaGumma
4,14512341
4,14512341
3
@CodyGray: Why have you removed the C++ tag? This has changed the correctness of some of the answers and subsequent comments?
– CB Bailey
Jan 17 '11 at 9:20
3
@CodyGray: C strings are still often used in C++. As for answers not being correct, that was my point; I downvoted an incorrect answer and you magically made it correct thus invalidating my downvote.
– CB Bailey
Jan 17 '11 at 9:27
2
@Charles Bailey I am mainly using C++, but of course I want to know is there any difference between C and C++ . That's why I add C++ tag.
– UmmaGumma
Jan 17 '11 at 9:38
2
@Ashot: Next time, please add that to your question. It's difficult to infer things like that from tags, and I'm really bad at reading people's minds. @Charles: Ultimately, I suppose, my aim was to reduce ambiguity. It seems you're arguing my side when you say the correctness of answers hinges on the tags in use. Like I said, feel free to rollback my edits if you disagree.
– Cody Gray♦
Jan 17 '11 at 9:41
3
@CodyGray: At one particular point in the cycle of edits an answer suggested that something likechar a[2] = "OK";
was OK. I immediately downvoted but as I was writing my comment I double checked the tags and noted that the question was now only about C.
– CB Bailey
Jan 17 '11 at 9:52
|
show 7 more comments
3
@CodyGray: Why have you removed the C++ tag? This has changed the correctness of some of the answers and subsequent comments?
– CB Bailey
Jan 17 '11 at 9:20
3
@CodyGray: C strings are still often used in C++. As for answers not being correct, that was my point; I downvoted an incorrect answer and you magically made it correct thus invalidating my downvote.
– CB Bailey
Jan 17 '11 at 9:27
2
@Charles Bailey I am mainly using C++, but of course I want to know is there any difference between C and C++ . That's why I add C++ tag.
– UmmaGumma
Jan 17 '11 at 9:38
2
@Ashot: Next time, please add that to your question. It's difficult to infer things like that from tags, and I'm really bad at reading people's minds. @Charles: Ultimately, I suppose, my aim was to reduce ambiguity. It seems you're arguing my side when you say the correctness of answers hinges on the tags in use. Like I said, feel free to rollback my edits if you disagree.
– Cody Gray♦
Jan 17 '11 at 9:41
3
@CodyGray: At one particular point in the cycle of edits an answer suggested that something likechar a[2] = "OK";
was OK. I immediately downvoted but as I was writing my comment I double checked the tags and noted that the question was now only about C.
– CB Bailey
Jan 17 '11 at 9:52
3
3
@CodyGray: Why have you removed the C++ tag? This has changed the correctness of some of the answers and subsequent comments?
– CB Bailey
Jan 17 '11 at 9:20
@CodyGray: Why have you removed the C++ tag? This has changed the correctness of some of the answers and subsequent comments?
– CB Bailey
Jan 17 '11 at 9:20
3
3
@CodyGray: C strings are still often used in C++. As for answers not being correct, that was my point; I downvoted an incorrect answer and you magically made it correct thus invalidating my downvote.
– CB Bailey
Jan 17 '11 at 9:27
@CodyGray: C strings are still often used in C++. As for answers not being correct, that was my point; I downvoted an incorrect answer and you magically made it correct thus invalidating my downvote.
– CB Bailey
Jan 17 '11 at 9:27
2
2
@Charles Bailey I am mainly using C++, but of course I want to know is there any difference between C and C++ . That's why I add C++ tag.
– UmmaGumma
Jan 17 '11 at 9:38
@Charles Bailey I am mainly using C++, but of course I want to know is there any difference between C and C++ . That's why I add C++ tag.
– UmmaGumma
Jan 17 '11 at 9:38
2
2
@Ashot: Next time, please add that to your question. It's difficult to infer things like that from tags, and I'm really bad at reading people's minds. @Charles: Ultimately, I suppose, my aim was to reduce ambiguity. It seems you're arguing my side when you say the correctness of answers hinges on the tags in use. Like I said, feel free to rollback my edits if you disagree.
– Cody Gray♦
Jan 17 '11 at 9:41
@Ashot: Next time, please add that to your question. It's difficult to infer things like that from tags, and I'm really bad at reading people's minds. @Charles: Ultimately, I suppose, my aim was to reduce ambiguity. It seems you're arguing my side when you say the correctness of answers hinges on the tags in use. Like I said, feel free to rollback my edits if you disagree.
– Cody Gray♦
Jan 17 '11 at 9:41
3
3
@CodyGray: At one particular point in the cycle of edits an answer suggested that something like
char a[2] = "OK";
was OK. I immediately downvoted but as I was writing my comment I double checked the tags and noted that the question was now only about C.– CB Bailey
Jan 17 '11 at 9:52
@CodyGray: At one particular point in the cycle of edits an answer suggested that something like
char a[2] = "OK";
was OK. I immediately downvoted but as I was writing my comment I double checked the tags and noted that the question was now only about C.– CB Bailey
Jan 17 '11 at 9:52
|
show 7 more comments
6 Answers
6
active
oldest
votes
up vote
82
down vote
accepted
sizeof str
is 7 - five bytes for the "Hello" text, plus the explicit NUL terminator, plus the implicit NUL terminator.
strlen(str)
is 5 - the five "Hello" bytes only.
The key here is that the implicit nul terminator is always added - even if the string literal just happens to end with . Of course,
strlen
just stops at the first - it can't tell the difference.
There is one exception to the implicit NUL terminator rule - if you explicitly specify the array size, the string will be truncated to fit:
char str[6] = "Hello"; // strlen(str) = 5, sizeof(str) = 6 (with one NUL)
char str[7] = "Hello"; // strlen(str) = 5, sizeof(str) = 7 (with two NULs)
char str[8] = "Hello"; // strlen(str) = 5, sizeof(str) = 8 (with three NULs per C99 6.7.8.21)
This is, however, rarely useful, and prone to miscalculating the string length and ending up with an unterminated string. It is also forbidden in C++.
5
You should add that this kind of truncation is only valid in C, not in C++.
– fredoverflow
Jan 17 '11 at 9:15
3
Yourchar [8]
example seems wrong. If the OP had usedchar str[8] = 'H', 'e', 'l', 'l', 'o', '', '' ; the remaining character's value would _not_ be undefined, it would be zero (so that you can sanely initialize, e.g.
int arr[100] = 0 ` to be all zeroes). I don't see why it would be any different for"Hello"
than it is for the long form, unless the standard explicitly makes an exception for this case (which would seem very strange to me.)
– Chris Lutz
Jan 17 '11 at 9:19
@Chris, yes, I updated it presumably while you were writing your response :)
– bdonlan
Jan 17 '11 at 9:50
1
Incidentally, the paragraph in question: If there are fewer initializers in a brace-enclosed list than there are elements or members of an aggregate, or fewer characters in a string literal used to initialize an array of known size than there are elements in the array, the remainder of the aggregate shall be initialized implicitly the same as objects that have static storage duration.
– bdonlan
Jan 17 '11 at 9:50
1
FYI, null character (also null terminator), abbreviated NUL, therefore the term "NUL terminator" is little bit confusing for me.
– V-SHY
Feb 17 '15 at 3:58
|
show 1 more comment
up vote
10
down vote
The length of the array is 7, the NUL character still counts as a character and the string is still terminated with an implicit
See this link to see a working example
Note that had you declared str
as char str[6]= "Hello";
the length would be 6 because the implicit NUL is only added if it can fit (which it can't in this example.)
§ 6.7.8/p14
An array of
character type may be initialized by a
character string literal, optionally
enclosed in braces. Sucessive
characters of the character string
literal (including the terminating
null character if there is room or if
the array is of unknown size)
initialize the elements of the array.
Examples
char str = "Hello"; /* sizeof == 7, Explicit + Implicit NUL */
char str[5]= "Hello"; /* sizeof == 5, str is "Hello" with no NUL (no longer a C-string, just an array of char). This may trigger compiler warning */
char str[6]= "Hello"; /* sizeof == 6, Explicit NUL only */
char str[7]= "Hello"; /* sizeof == 7, Explicit + Implicit NUL */
char str[8]= "Hello"; /* sizeof == 8, Explicit + two Implicit NUL */
The length of the "string" (as C functions view strings) is 5. Thesizeof
operator returns 7.
– Chris Lutz
Jan 17 '11 at 9:07
2
@ChrisLutz: The question asked was "What is the length of str array " (my emphasis) so this answer is correct.
– CB Bailey
Jan 17 '11 at 9:11
1
@Chris Ok, I'll concede that theC
vernacular has different meanings for length and size with respect to strings. In my answer I was referring to the latter.
– SiegeX
Jan 17 '11 at 9:12
add a comment |
up vote
5
down vote
Banging my usual drum solo of JUST TRY IT, here's how you can answer questions like that in the future:
$ cat junk.c
#include <stdio.h>
char* string = "Hello";
int main(int argv, char** argc)
printf("-->%s<--n", string);
$ gcc -S junk.c
$ cat junk.s
... eliding the unnecessary parts ...
.LC0:
.string "Hello"
.string ""
...
.LC1:
.string "-->%s<--n"
...
Note here how the string I used for printf is just "-->%s<---n"
while the global string is in two parts: "Hello"
and ""
. The GNU assembler also terminates strings with an implicit NUL
character, so the fact that the first string (.LC0) is in those two parts indicates that there are two NUL
s. The string is thus 7 bytes long. Generally if you really want to know what your compiler is doing with a certain hunk of code, isolate it in a dummy example like this and see what it's doing using -S
(for GNU -- MSVC has a flag too for assembler output but I don't know it off-hand). You'll learn a lot about how your code works (or fails to work as the case may be) and you'll get an answer quickly that is 100% guaranteed to match the tools and environment you're working in.
2
... unless the thing we're testing happens to be undefined behavior, in which case the answer might only be 100% guaranteed to match the tools and environment at the moment it's tested. Furthermore, if the thing we're testing is implementation-defined, then to really get the answer, we'd have to test it on all possible implementations. (And we'd also have to know it's implementation-defined, but if we already knew that, we wouldn't have had to ask.) Furthermore, to test in this way, we'll need to know the rules for GNU assembler as well as the language we're actually trying to work in.
– Rob Kennedy
Jan 17 '11 at 15:12
add a comment |
up vote
3
down vote
What is the length of str array, and with how much 0s it is ending?
Let's find out:
int main()
char str = "Hello";
int length = sizeof str / sizeof str[0];
// "sizeof array" is the bytes for the whole array (must use a real array, not
// a pointer), divide by "sizeof array[0]" (sometimes sizeof *array is used)
// to get the number of items in the array
printf("array length: %dn", length);
printf("last 3 bytes: %02x %02x %02xn",
str[length - 3], str[length - 2], str[length - 1]);
return 0;
add a comment |
up vote
3
down vote
Specifically, I want to mention one situation, by which you may confuse.
What is the difference between "" and ""?
The answer is that ""
represents in array is 0 0
and ""
is 0
.
Because ""
is still a string literal and it will also add ""
at the end of it. And ""
is empty but also add ""
.
Understanding of this will help you understand ""
deeply.
In other words, the empty-string is still null-terminated in C.
– David C. Rankin
Oct 28 '15 at 7:58
add a comment |
up vote
0
down vote
char str= "Hello";
That would be 7 bytes.
In memory it'd be:
48 65 6C 6C 6F 00 00
H e l l o
Edit:
What does the symbol mean in a C string?
It's the "end" of a string. A null character. In memory, it's actually a Zero. Usually functions that handle char arrays look for this character, as this is the end of the message. I'll put an example at the end.What is the length of str array? (Answered before the edit part)
7and with how much 0s it is ending?
You array has two "spaces" with zero; str[5]=str[6]=''=0
Extra example:
Let's assume you have a function that prints the content of that text array.
You could define it as:
char str[40];
Now, you could change the content of that array (I won't get into details on how to), so that it contains the message: "This is just a printing test"
In memory, you should have something like:
54 68 69 73 20 69 73 20 6a 75 73 74 20 61 20 70 72 69 6e 74
69 6e 67 20 74 65 73 74 00 00 00 00 00 00 00 00 00 00 00 00
So you print that char array. And then you want a new message. Let's say just "Hello"
48 65 6c 6c 6f 00 73 20 6a 75 73 74 20 61 20 70 72 69 6e 74
69 6e 67 20 74 65 73 74 00 00 00 00 00 00 00 00 00 00 00 00
Notice the 00 on str[5]. That's how the print function will know how much it actually needs to send, despite the actual longitude of the vector and the whole content.
You are not answering the original question "what does the symbol mean". Please expand your answer to address the original question.
– Michal
Nov 8 at 20:28
Other answers already mention thatstr
is an array of size 7, including the accepted answer from seven years ago. Why repeat it yet again (without adding anything new)?
– melpomene
Nov 8 at 20:37
@Michal, you do realize the original post has 3 questions, right?
– L. Lopez
Nov 10 at 18:18
@melpomene. I do apologize for that. I expanded the answer and hopefully it clarifies further and adds more, as you seem to want.
– L. Lopez
Nov 10 at 18:20
add a comment |
protected by melpomene Nov 8 at 20:35
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6 Answers
6
active
oldest
votes
6 Answers
6
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
82
down vote
accepted
sizeof str
is 7 - five bytes for the "Hello" text, plus the explicit NUL terminator, plus the implicit NUL terminator.
strlen(str)
is 5 - the five "Hello" bytes only.
The key here is that the implicit nul terminator is always added - even if the string literal just happens to end with . Of course,
strlen
just stops at the first - it can't tell the difference.
There is one exception to the implicit NUL terminator rule - if you explicitly specify the array size, the string will be truncated to fit:
char str[6] = "Hello"; // strlen(str) = 5, sizeof(str) = 6 (with one NUL)
char str[7] = "Hello"; // strlen(str) = 5, sizeof(str) = 7 (with two NULs)
char str[8] = "Hello"; // strlen(str) = 5, sizeof(str) = 8 (with three NULs per C99 6.7.8.21)
This is, however, rarely useful, and prone to miscalculating the string length and ending up with an unterminated string. It is also forbidden in C++.
5
You should add that this kind of truncation is only valid in C, not in C++.
– fredoverflow
Jan 17 '11 at 9:15
3
Yourchar [8]
example seems wrong. If the OP had usedchar str[8] = 'H', 'e', 'l', 'l', 'o', '', '' ; the remaining character's value would _not_ be undefined, it would be zero (so that you can sanely initialize, e.g.
int arr[100] = 0 ` to be all zeroes). I don't see why it would be any different for"Hello"
than it is for the long form, unless the standard explicitly makes an exception for this case (which would seem very strange to me.)
– Chris Lutz
Jan 17 '11 at 9:19
@Chris, yes, I updated it presumably while you were writing your response :)
– bdonlan
Jan 17 '11 at 9:50
1
Incidentally, the paragraph in question: If there are fewer initializers in a brace-enclosed list than there are elements or members of an aggregate, or fewer characters in a string literal used to initialize an array of known size than there are elements in the array, the remainder of the aggregate shall be initialized implicitly the same as objects that have static storage duration.
– bdonlan
Jan 17 '11 at 9:50
1
FYI, null character (also null terminator), abbreviated NUL, therefore the term "NUL terminator" is little bit confusing for me.
– V-SHY
Feb 17 '15 at 3:58
|
show 1 more comment
up vote
82
down vote
accepted
sizeof str
is 7 - five bytes for the "Hello" text, plus the explicit NUL terminator, plus the implicit NUL terminator.
strlen(str)
is 5 - the five "Hello" bytes only.
The key here is that the implicit nul terminator is always added - even if the string literal just happens to end with . Of course,
strlen
just stops at the first - it can't tell the difference.
There is one exception to the implicit NUL terminator rule - if you explicitly specify the array size, the string will be truncated to fit:
char str[6] = "Hello"; // strlen(str) = 5, sizeof(str) = 6 (with one NUL)
char str[7] = "Hello"; // strlen(str) = 5, sizeof(str) = 7 (with two NULs)
char str[8] = "Hello"; // strlen(str) = 5, sizeof(str) = 8 (with three NULs per C99 6.7.8.21)
This is, however, rarely useful, and prone to miscalculating the string length and ending up with an unterminated string. It is also forbidden in C++.
5
You should add that this kind of truncation is only valid in C, not in C++.
– fredoverflow
Jan 17 '11 at 9:15
3
Yourchar [8]
example seems wrong. If the OP had usedchar str[8] = 'H', 'e', 'l', 'l', 'o', '', '' ; the remaining character's value would _not_ be undefined, it would be zero (so that you can sanely initialize, e.g.
int arr[100] = 0 ` to be all zeroes). I don't see why it would be any different for"Hello"
than it is for the long form, unless the standard explicitly makes an exception for this case (which would seem very strange to me.)
– Chris Lutz
Jan 17 '11 at 9:19
@Chris, yes, I updated it presumably while you were writing your response :)
– bdonlan
Jan 17 '11 at 9:50
1
Incidentally, the paragraph in question: If there are fewer initializers in a brace-enclosed list than there are elements or members of an aggregate, or fewer characters in a string literal used to initialize an array of known size than there are elements in the array, the remainder of the aggregate shall be initialized implicitly the same as objects that have static storage duration.
– bdonlan
Jan 17 '11 at 9:50
1
FYI, null character (also null terminator), abbreviated NUL, therefore the term "NUL terminator" is little bit confusing for me.
– V-SHY
Feb 17 '15 at 3:58
|
show 1 more comment
up vote
82
down vote
accepted
up vote
82
down vote
accepted
sizeof str
is 7 - five bytes for the "Hello" text, plus the explicit NUL terminator, plus the implicit NUL terminator.
strlen(str)
is 5 - the five "Hello" bytes only.
The key here is that the implicit nul terminator is always added - even if the string literal just happens to end with . Of course,
strlen
just stops at the first - it can't tell the difference.
There is one exception to the implicit NUL terminator rule - if you explicitly specify the array size, the string will be truncated to fit:
char str[6] = "Hello"; // strlen(str) = 5, sizeof(str) = 6 (with one NUL)
char str[7] = "Hello"; // strlen(str) = 5, sizeof(str) = 7 (with two NULs)
char str[8] = "Hello"; // strlen(str) = 5, sizeof(str) = 8 (with three NULs per C99 6.7.8.21)
This is, however, rarely useful, and prone to miscalculating the string length and ending up with an unterminated string. It is also forbidden in C++.
sizeof str
is 7 - five bytes for the "Hello" text, plus the explicit NUL terminator, plus the implicit NUL terminator.
strlen(str)
is 5 - the five "Hello" bytes only.
The key here is that the implicit nul terminator is always added - even if the string literal just happens to end with . Of course,
strlen
just stops at the first - it can't tell the difference.
There is one exception to the implicit NUL terminator rule - if you explicitly specify the array size, the string will be truncated to fit:
char str[6] = "Hello"; // strlen(str) = 5, sizeof(str) = 6 (with one NUL)
char str[7] = "Hello"; // strlen(str) = 5, sizeof(str) = 7 (with two NULs)
char str[8] = "Hello"; // strlen(str) = 5, sizeof(str) = 8 (with three NULs per C99 6.7.8.21)
This is, however, rarely useful, and prone to miscalculating the string length and ending up with an unterminated string. It is also forbidden in C++.
edited Jan 17 '11 at 9:17
answered Jan 17 '11 at 9:05
bdonlan
172k21220297
172k21220297
5
You should add that this kind of truncation is only valid in C, not in C++.
– fredoverflow
Jan 17 '11 at 9:15
3
Yourchar [8]
example seems wrong. If the OP had usedchar str[8] = 'H', 'e', 'l', 'l', 'o', '', '' ; the remaining character's value would _not_ be undefined, it would be zero (so that you can sanely initialize, e.g.
int arr[100] = 0 ` to be all zeroes). I don't see why it would be any different for"Hello"
than it is for the long form, unless the standard explicitly makes an exception for this case (which would seem very strange to me.)
– Chris Lutz
Jan 17 '11 at 9:19
@Chris, yes, I updated it presumably while you were writing your response :)
– bdonlan
Jan 17 '11 at 9:50
1
Incidentally, the paragraph in question: If there are fewer initializers in a brace-enclosed list than there are elements or members of an aggregate, or fewer characters in a string literal used to initialize an array of known size than there are elements in the array, the remainder of the aggregate shall be initialized implicitly the same as objects that have static storage duration.
– bdonlan
Jan 17 '11 at 9:50
1
FYI, null character (also null terminator), abbreviated NUL, therefore the term "NUL terminator" is little bit confusing for me.
– V-SHY
Feb 17 '15 at 3:58
|
show 1 more comment
5
You should add that this kind of truncation is only valid in C, not in C++.
– fredoverflow
Jan 17 '11 at 9:15
3
Yourchar [8]
example seems wrong. If the OP had usedchar str[8] = 'H', 'e', 'l', 'l', 'o', '', '' ; the remaining character's value would _not_ be undefined, it would be zero (so that you can sanely initialize, e.g.
int arr[100] = 0 ` to be all zeroes). I don't see why it would be any different for"Hello"
than it is for the long form, unless the standard explicitly makes an exception for this case (which would seem very strange to me.)
– Chris Lutz
Jan 17 '11 at 9:19
@Chris, yes, I updated it presumably while you were writing your response :)
– bdonlan
Jan 17 '11 at 9:50
1
Incidentally, the paragraph in question: If there are fewer initializers in a brace-enclosed list than there are elements or members of an aggregate, or fewer characters in a string literal used to initialize an array of known size than there are elements in the array, the remainder of the aggregate shall be initialized implicitly the same as objects that have static storage duration.
– bdonlan
Jan 17 '11 at 9:50
1
FYI, null character (also null terminator), abbreviated NUL, therefore the term "NUL terminator" is little bit confusing for me.
– V-SHY
Feb 17 '15 at 3:58
5
5
You should add that this kind of truncation is only valid in C, not in C++.
– fredoverflow
Jan 17 '11 at 9:15
You should add that this kind of truncation is only valid in C, not in C++.
– fredoverflow
Jan 17 '11 at 9:15
3
3
Your
char [8]
example seems wrong. If the OP had used char str[8] = 'H', 'e', 'l', 'l', 'o', '', '' ; the remaining character's value would _not_ be undefined, it would be zero (so that you can sanely initialize, e.g.
int arr[100] = 0 ` to be all zeroes). I don't see why it would be any different for "Hello"
than it is for the long form, unless the standard explicitly makes an exception for this case (which would seem very strange to me.)– Chris Lutz
Jan 17 '11 at 9:19
Your
char [8]
example seems wrong. If the OP had used char str[8] = 'H', 'e', 'l', 'l', 'o', '', '' ; the remaining character's value would _not_ be undefined, it would be zero (so that you can sanely initialize, e.g.
int arr[100] = 0 ` to be all zeroes). I don't see why it would be any different for "Hello"
than it is for the long form, unless the standard explicitly makes an exception for this case (which would seem very strange to me.)– Chris Lutz
Jan 17 '11 at 9:19
@Chris, yes, I updated it presumably while you were writing your response :)
– bdonlan
Jan 17 '11 at 9:50
@Chris, yes, I updated it presumably while you were writing your response :)
– bdonlan
Jan 17 '11 at 9:50
1
1
Incidentally, the paragraph in question: If there are fewer initializers in a brace-enclosed list than there are elements or members of an aggregate, or fewer characters in a string literal used to initialize an array of known size than there are elements in the array, the remainder of the aggregate shall be initialized implicitly the same as objects that have static storage duration.
– bdonlan
Jan 17 '11 at 9:50
Incidentally, the paragraph in question: If there are fewer initializers in a brace-enclosed list than there are elements or members of an aggregate, or fewer characters in a string literal used to initialize an array of known size than there are elements in the array, the remainder of the aggregate shall be initialized implicitly the same as objects that have static storage duration.
– bdonlan
Jan 17 '11 at 9:50
1
1
FYI, null character (also null terminator), abbreviated NUL, therefore the term "NUL terminator" is little bit confusing for me.
– V-SHY
Feb 17 '15 at 3:58
FYI, null character (also null terminator), abbreviated NUL, therefore the term "NUL terminator" is little bit confusing for me.
– V-SHY
Feb 17 '15 at 3:58
|
show 1 more comment
up vote
10
down vote
The length of the array is 7, the NUL character still counts as a character and the string is still terminated with an implicit
See this link to see a working example
Note that had you declared str
as char str[6]= "Hello";
the length would be 6 because the implicit NUL is only added if it can fit (which it can't in this example.)
§ 6.7.8/p14
An array of
character type may be initialized by a
character string literal, optionally
enclosed in braces. Sucessive
characters of the character string
literal (including the terminating
null character if there is room or if
the array is of unknown size)
initialize the elements of the array.
Examples
char str = "Hello"; /* sizeof == 7, Explicit + Implicit NUL */
char str[5]= "Hello"; /* sizeof == 5, str is "Hello" with no NUL (no longer a C-string, just an array of char). This may trigger compiler warning */
char str[6]= "Hello"; /* sizeof == 6, Explicit NUL only */
char str[7]= "Hello"; /* sizeof == 7, Explicit + Implicit NUL */
char str[8]= "Hello"; /* sizeof == 8, Explicit + two Implicit NUL */
The length of the "string" (as C functions view strings) is 5. Thesizeof
operator returns 7.
– Chris Lutz
Jan 17 '11 at 9:07
2
@ChrisLutz: The question asked was "What is the length of str array " (my emphasis) so this answer is correct.
– CB Bailey
Jan 17 '11 at 9:11
1
@Chris Ok, I'll concede that theC
vernacular has different meanings for length and size with respect to strings. In my answer I was referring to the latter.
– SiegeX
Jan 17 '11 at 9:12
add a comment |
up vote
10
down vote
The length of the array is 7, the NUL character still counts as a character and the string is still terminated with an implicit
See this link to see a working example
Note that had you declared str
as char str[6]= "Hello";
the length would be 6 because the implicit NUL is only added if it can fit (which it can't in this example.)
§ 6.7.8/p14
An array of
character type may be initialized by a
character string literal, optionally
enclosed in braces. Sucessive
characters of the character string
literal (including the terminating
null character if there is room or if
the array is of unknown size)
initialize the elements of the array.
Examples
char str = "Hello"; /* sizeof == 7, Explicit + Implicit NUL */
char str[5]= "Hello"; /* sizeof == 5, str is "Hello" with no NUL (no longer a C-string, just an array of char). This may trigger compiler warning */
char str[6]= "Hello"; /* sizeof == 6, Explicit NUL only */
char str[7]= "Hello"; /* sizeof == 7, Explicit + Implicit NUL */
char str[8]= "Hello"; /* sizeof == 8, Explicit + two Implicit NUL */
The length of the "string" (as C functions view strings) is 5. Thesizeof
operator returns 7.
– Chris Lutz
Jan 17 '11 at 9:07
2
@ChrisLutz: The question asked was "What is the length of str array " (my emphasis) so this answer is correct.
– CB Bailey
Jan 17 '11 at 9:11
1
@Chris Ok, I'll concede that theC
vernacular has different meanings for length and size with respect to strings. In my answer I was referring to the latter.
– SiegeX
Jan 17 '11 at 9:12
add a comment |
up vote
10
down vote
up vote
10
down vote
The length of the array is 7, the NUL character still counts as a character and the string is still terminated with an implicit
See this link to see a working example
Note that had you declared str
as char str[6]= "Hello";
the length would be 6 because the implicit NUL is only added if it can fit (which it can't in this example.)
§ 6.7.8/p14
An array of
character type may be initialized by a
character string literal, optionally
enclosed in braces. Sucessive
characters of the character string
literal (including the terminating
null character if there is room or if
the array is of unknown size)
initialize the elements of the array.
Examples
char str = "Hello"; /* sizeof == 7, Explicit + Implicit NUL */
char str[5]= "Hello"; /* sizeof == 5, str is "Hello" with no NUL (no longer a C-string, just an array of char). This may trigger compiler warning */
char str[6]= "Hello"; /* sizeof == 6, Explicit NUL only */
char str[7]= "Hello"; /* sizeof == 7, Explicit + Implicit NUL */
char str[8]= "Hello"; /* sizeof == 8, Explicit + two Implicit NUL */
The length of the array is 7, the NUL character still counts as a character and the string is still terminated with an implicit
See this link to see a working example
Note that had you declared str
as char str[6]= "Hello";
the length would be 6 because the implicit NUL is only added if it can fit (which it can't in this example.)
§ 6.7.8/p14
An array of
character type may be initialized by a
character string literal, optionally
enclosed in braces. Sucessive
characters of the character string
literal (including the terminating
null character if there is room or if
the array is of unknown size)
initialize the elements of the array.
Examples
char str = "Hello"; /* sizeof == 7, Explicit + Implicit NUL */
char str[5]= "Hello"; /* sizeof == 5, str is "Hello" with no NUL (no longer a C-string, just an array of char). This may trigger compiler warning */
char str[6]= "Hello"; /* sizeof == 6, Explicit NUL only */
char str[7]= "Hello"; /* sizeof == 7, Explicit + Implicit NUL */
char str[8]= "Hello"; /* sizeof == 8, Explicit + two Implicit NUL */
edited Jan 17 '11 at 9:27
answered Jan 17 '11 at 9:03
SiegeX
89.4k17112143
89.4k17112143
The length of the "string" (as C functions view strings) is 5. Thesizeof
operator returns 7.
– Chris Lutz
Jan 17 '11 at 9:07
2
@ChrisLutz: The question asked was "What is the length of str array " (my emphasis) so this answer is correct.
– CB Bailey
Jan 17 '11 at 9:11
1
@Chris Ok, I'll concede that theC
vernacular has different meanings for length and size with respect to strings. In my answer I was referring to the latter.
– SiegeX
Jan 17 '11 at 9:12
add a comment |
The length of the "string" (as C functions view strings) is 5. Thesizeof
operator returns 7.
– Chris Lutz
Jan 17 '11 at 9:07
2
@ChrisLutz: The question asked was "What is the length of str array " (my emphasis) so this answer is correct.
– CB Bailey
Jan 17 '11 at 9:11
1
@Chris Ok, I'll concede that theC
vernacular has different meanings for length and size with respect to strings. In my answer I was referring to the latter.
– SiegeX
Jan 17 '11 at 9:12
The length of the "string" (as C functions view strings) is 5. The
sizeof
operator returns 7.– Chris Lutz
Jan 17 '11 at 9:07
The length of the "string" (as C functions view strings) is 5. The
sizeof
operator returns 7.– Chris Lutz
Jan 17 '11 at 9:07
2
2
@ChrisLutz: The question asked was "What is the length of str array " (my emphasis) so this answer is correct.
– CB Bailey
Jan 17 '11 at 9:11
@ChrisLutz: The question asked was "What is the length of str array " (my emphasis) so this answer is correct.
– CB Bailey
Jan 17 '11 at 9:11
1
1
@Chris Ok, I'll concede that the
C
vernacular has different meanings for length and size with respect to strings. In my answer I was referring to the latter.– SiegeX
Jan 17 '11 at 9:12
@Chris Ok, I'll concede that the
C
vernacular has different meanings for length and size with respect to strings. In my answer I was referring to the latter.– SiegeX
Jan 17 '11 at 9:12
add a comment |
up vote
5
down vote
Banging my usual drum solo of JUST TRY IT, here's how you can answer questions like that in the future:
$ cat junk.c
#include <stdio.h>
char* string = "Hello";
int main(int argv, char** argc)
printf("-->%s<--n", string);
$ gcc -S junk.c
$ cat junk.s
... eliding the unnecessary parts ...
.LC0:
.string "Hello"
.string ""
...
.LC1:
.string "-->%s<--n"
...
Note here how the string I used for printf is just "-->%s<---n"
while the global string is in two parts: "Hello"
and ""
. The GNU assembler also terminates strings with an implicit NUL
character, so the fact that the first string (.LC0) is in those two parts indicates that there are two NUL
s. The string is thus 7 bytes long. Generally if you really want to know what your compiler is doing with a certain hunk of code, isolate it in a dummy example like this and see what it's doing using -S
(for GNU -- MSVC has a flag too for assembler output but I don't know it off-hand). You'll learn a lot about how your code works (or fails to work as the case may be) and you'll get an answer quickly that is 100% guaranteed to match the tools and environment you're working in.
2
... unless the thing we're testing happens to be undefined behavior, in which case the answer might only be 100% guaranteed to match the tools and environment at the moment it's tested. Furthermore, if the thing we're testing is implementation-defined, then to really get the answer, we'd have to test it on all possible implementations. (And we'd also have to know it's implementation-defined, but if we already knew that, we wouldn't have had to ask.) Furthermore, to test in this way, we'll need to know the rules for GNU assembler as well as the language we're actually trying to work in.
– Rob Kennedy
Jan 17 '11 at 15:12
add a comment |
up vote
5
down vote
Banging my usual drum solo of JUST TRY IT, here's how you can answer questions like that in the future:
$ cat junk.c
#include <stdio.h>
char* string = "Hello";
int main(int argv, char** argc)
printf("-->%s<--n", string);
$ gcc -S junk.c
$ cat junk.s
... eliding the unnecessary parts ...
.LC0:
.string "Hello"
.string ""
...
.LC1:
.string "-->%s<--n"
...
Note here how the string I used for printf is just "-->%s<---n"
while the global string is in two parts: "Hello"
and ""
. The GNU assembler also terminates strings with an implicit NUL
character, so the fact that the first string (.LC0) is in those two parts indicates that there are two NUL
s. The string is thus 7 bytes long. Generally if you really want to know what your compiler is doing with a certain hunk of code, isolate it in a dummy example like this and see what it's doing using -S
(for GNU -- MSVC has a flag too for assembler output but I don't know it off-hand). You'll learn a lot about how your code works (or fails to work as the case may be) and you'll get an answer quickly that is 100% guaranteed to match the tools and environment you're working in.
2
... unless the thing we're testing happens to be undefined behavior, in which case the answer might only be 100% guaranteed to match the tools and environment at the moment it's tested. Furthermore, if the thing we're testing is implementation-defined, then to really get the answer, we'd have to test it on all possible implementations. (And we'd also have to know it's implementation-defined, but if we already knew that, we wouldn't have had to ask.) Furthermore, to test in this way, we'll need to know the rules for GNU assembler as well as the language we're actually trying to work in.
– Rob Kennedy
Jan 17 '11 at 15:12
add a comment |
up vote
5
down vote
up vote
5
down vote
Banging my usual drum solo of JUST TRY IT, here's how you can answer questions like that in the future:
$ cat junk.c
#include <stdio.h>
char* string = "Hello";
int main(int argv, char** argc)
printf("-->%s<--n", string);
$ gcc -S junk.c
$ cat junk.s
... eliding the unnecessary parts ...
.LC0:
.string "Hello"
.string ""
...
.LC1:
.string "-->%s<--n"
...
Note here how the string I used for printf is just "-->%s<---n"
while the global string is in two parts: "Hello"
and ""
. The GNU assembler also terminates strings with an implicit NUL
character, so the fact that the first string (.LC0) is in those two parts indicates that there are two NUL
s. The string is thus 7 bytes long. Generally if you really want to know what your compiler is doing with a certain hunk of code, isolate it in a dummy example like this and see what it's doing using -S
(for GNU -- MSVC has a flag too for assembler output but I don't know it off-hand). You'll learn a lot about how your code works (or fails to work as the case may be) and you'll get an answer quickly that is 100% guaranteed to match the tools and environment you're working in.
Banging my usual drum solo of JUST TRY IT, here's how you can answer questions like that in the future:
$ cat junk.c
#include <stdio.h>
char* string = "Hello";
int main(int argv, char** argc)
printf("-->%s<--n", string);
$ gcc -S junk.c
$ cat junk.s
... eliding the unnecessary parts ...
.LC0:
.string "Hello"
.string ""
...
.LC1:
.string "-->%s<--n"
...
Note here how the string I used for printf is just "-->%s<---n"
while the global string is in two parts: "Hello"
and ""
. The GNU assembler also terminates strings with an implicit NUL
character, so the fact that the first string (.LC0) is in those two parts indicates that there are two NUL
s. The string is thus 7 bytes long. Generally if you really want to know what your compiler is doing with a certain hunk of code, isolate it in a dummy example like this and see what it's doing using -S
(for GNU -- MSVC has a flag too for assembler output but I don't know it off-hand). You'll learn a lot about how your code works (or fails to work as the case may be) and you'll get an answer quickly that is 100% guaranteed to match the tools and environment you're working in.
answered Jan 17 '11 at 9:21
JUST MY correct OPINION
28.1k146694
28.1k146694
2
... unless the thing we're testing happens to be undefined behavior, in which case the answer might only be 100% guaranteed to match the tools and environment at the moment it's tested. Furthermore, if the thing we're testing is implementation-defined, then to really get the answer, we'd have to test it on all possible implementations. (And we'd also have to know it's implementation-defined, but if we already knew that, we wouldn't have had to ask.) Furthermore, to test in this way, we'll need to know the rules for GNU assembler as well as the language we're actually trying to work in.
– Rob Kennedy
Jan 17 '11 at 15:12
add a comment |
2
... unless the thing we're testing happens to be undefined behavior, in which case the answer might only be 100% guaranteed to match the tools and environment at the moment it's tested. Furthermore, if the thing we're testing is implementation-defined, then to really get the answer, we'd have to test it on all possible implementations. (And we'd also have to know it's implementation-defined, but if we already knew that, we wouldn't have had to ask.) Furthermore, to test in this way, we'll need to know the rules for GNU assembler as well as the language we're actually trying to work in.
– Rob Kennedy
Jan 17 '11 at 15:12
2
2
... unless the thing we're testing happens to be undefined behavior, in which case the answer might only be 100% guaranteed to match the tools and environment at the moment it's tested. Furthermore, if the thing we're testing is implementation-defined, then to really get the answer, we'd have to test it on all possible implementations. (And we'd also have to know it's implementation-defined, but if we already knew that, we wouldn't have had to ask.) Furthermore, to test in this way, we'll need to know the rules for GNU assembler as well as the language we're actually trying to work in.
– Rob Kennedy
Jan 17 '11 at 15:12
... unless the thing we're testing happens to be undefined behavior, in which case the answer might only be 100% guaranteed to match the tools and environment at the moment it's tested. Furthermore, if the thing we're testing is implementation-defined, then to really get the answer, we'd have to test it on all possible implementations. (And we'd also have to know it's implementation-defined, but if we already knew that, we wouldn't have had to ask.) Furthermore, to test in this way, we'll need to know the rules for GNU assembler as well as the language we're actually trying to work in.
– Rob Kennedy
Jan 17 '11 at 15:12
add a comment |
up vote
3
down vote
What is the length of str array, and with how much 0s it is ending?
Let's find out:
int main()
char str = "Hello";
int length = sizeof str / sizeof str[0];
// "sizeof array" is the bytes for the whole array (must use a real array, not
// a pointer), divide by "sizeof array[0]" (sometimes sizeof *array is used)
// to get the number of items in the array
printf("array length: %dn", length);
printf("last 3 bytes: %02x %02x %02xn",
str[length - 3], str[length - 2], str[length - 1]);
return 0;
add a comment |
up vote
3
down vote
What is the length of str array, and with how much 0s it is ending?
Let's find out:
int main()
char str = "Hello";
int length = sizeof str / sizeof str[0];
// "sizeof array" is the bytes for the whole array (must use a real array, not
// a pointer), divide by "sizeof array[0]" (sometimes sizeof *array is used)
// to get the number of items in the array
printf("array length: %dn", length);
printf("last 3 bytes: %02x %02x %02xn",
str[length - 3], str[length - 2], str[length - 1]);
return 0;
add a comment |
up vote
3
down vote
up vote
3
down vote
What is the length of str array, and with how much 0s it is ending?
Let's find out:
int main()
char str = "Hello";
int length = sizeof str / sizeof str[0];
// "sizeof array" is the bytes for the whole array (must use a real array, not
// a pointer), divide by "sizeof array[0]" (sometimes sizeof *array is used)
// to get the number of items in the array
printf("array length: %dn", length);
printf("last 3 bytes: %02x %02x %02xn",
str[length - 3], str[length - 2], str[length - 1]);
return 0;
What is the length of str array, and with how much 0s it is ending?
Let's find out:
int main()
char str = "Hello";
int length = sizeof str / sizeof str[0];
// "sizeof array" is the bytes for the whole array (must use a real array, not
// a pointer), divide by "sizeof array[0]" (sometimes sizeof *array is used)
// to get the number of items in the array
printf("array length: %dn", length);
printf("last 3 bytes: %02x %02x %02xn",
str[length - 3], str[length - 2], str[length - 1]);
return 0;
answered Jan 17 '11 at 9:48
Fred Nurk
11.6k32957
11.6k32957
add a comment |
add a comment |
up vote
3
down vote
Specifically, I want to mention one situation, by which you may confuse.
What is the difference between "" and ""?
The answer is that ""
represents in array is 0 0
and ""
is 0
.
Because ""
is still a string literal and it will also add ""
at the end of it. And ""
is empty but also add ""
.
Understanding of this will help you understand ""
deeply.
In other words, the empty-string is still null-terminated in C.
– David C. Rankin
Oct 28 '15 at 7:58
add a comment |
up vote
3
down vote
Specifically, I want to mention one situation, by which you may confuse.
What is the difference between "" and ""?
The answer is that ""
represents in array is 0 0
and ""
is 0
.
Because ""
is still a string literal and it will also add ""
at the end of it. And ""
is empty but also add ""
.
Understanding of this will help you understand ""
deeply.
In other words, the empty-string is still null-terminated in C.
– David C. Rankin
Oct 28 '15 at 7:58
add a comment |
up vote
3
down vote
up vote
3
down vote
Specifically, I want to mention one situation, by which you may confuse.
What is the difference between "" and ""?
The answer is that ""
represents in array is 0 0
and ""
is 0
.
Because ""
is still a string literal and it will also add ""
at the end of it. And ""
is empty but also add ""
.
Understanding of this will help you understand ""
deeply.
Specifically, I want to mention one situation, by which you may confuse.
What is the difference between "" and ""?
The answer is that ""
represents in array is 0 0
and ""
is 0
.
Because ""
is still a string literal and it will also add ""
at the end of it. And ""
is empty but also add ""
.
Understanding of this will help you understand ""
deeply.
edited Jul 4 '17 at 7:39
answered Oct 28 '15 at 7:13
YongHao Hu
1,384815
1,384815
In other words, the empty-string is still null-terminated in C.
– David C. Rankin
Oct 28 '15 at 7:58
add a comment |
In other words, the empty-string is still null-terminated in C.
– David C. Rankin
Oct 28 '15 at 7:58
In other words, the empty-string is still null-terminated in C.
– David C. Rankin
Oct 28 '15 at 7:58
In other words, the empty-string is still null-terminated in C.
– David C. Rankin
Oct 28 '15 at 7:58
add a comment |
up vote
0
down vote
char str= "Hello";
That would be 7 bytes.
In memory it'd be:
48 65 6C 6C 6F 00 00
H e l l o
Edit:
What does the symbol mean in a C string?
It's the "end" of a string. A null character. In memory, it's actually a Zero. Usually functions that handle char arrays look for this character, as this is the end of the message. I'll put an example at the end.What is the length of str array? (Answered before the edit part)
7and with how much 0s it is ending?
You array has two "spaces" with zero; str[5]=str[6]=''=0
Extra example:
Let's assume you have a function that prints the content of that text array.
You could define it as:
char str[40];
Now, you could change the content of that array (I won't get into details on how to), so that it contains the message: "This is just a printing test"
In memory, you should have something like:
54 68 69 73 20 69 73 20 6a 75 73 74 20 61 20 70 72 69 6e 74
69 6e 67 20 74 65 73 74 00 00 00 00 00 00 00 00 00 00 00 00
So you print that char array. And then you want a new message. Let's say just "Hello"
48 65 6c 6c 6f 00 73 20 6a 75 73 74 20 61 20 70 72 69 6e 74
69 6e 67 20 74 65 73 74 00 00 00 00 00 00 00 00 00 00 00 00
Notice the 00 on str[5]. That's how the print function will know how much it actually needs to send, despite the actual longitude of the vector and the whole content.
You are not answering the original question "what does the symbol mean". Please expand your answer to address the original question.
– Michal
Nov 8 at 20:28
Other answers already mention thatstr
is an array of size 7, including the accepted answer from seven years ago. Why repeat it yet again (without adding anything new)?
– melpomene
Nov 8 at 20:37
@Michal, you do realize the original post has 3 questions, right?
– L. Lopez
Nov 10 at 18:18
@melpomene. I do apologize for that. I expanded the answer and hopefully it clarifies further and adds more, as you seem to want.
– L. Lopez
Nov 10 at 18:20
add a comment |
up vote
0
down vote
char str= "Hello";
That would be 7 bytes.
In memory it'd be:
48 65 6C 6C 6F 00 00
H e l l o
Edit:
What does the symbol mean in a C string?
It's the "end" of a string. A null character. In memory, it's actually a Zero. Usually functions that handle char arrays look for this character, as this is the end of the message. I'll put an example at the end.What is the length of str array? (Answered before the edit part)
7and with how much 0s it is ending?
You array has two "spaces" with zero; str[5]=str[6]=''=0
Extra example:
Let's assume you have a function that prints the content of that text array.
You could define it as:
char str[40];
Now, you could change the content of that array (I won't get into details on how to), so that it contains the message: "This is just a printing test"
In memory, you should have something like:
54 68 69 73 20 69 73 20 6a 75 73 74 20 61 20 70 72 69 6e 74
69 6e 67 20 74 65 73 74 00 00 00 00 00 00 00 00 00 00 00 00
So you print that char array. And then you want a new message. Let's say just "Hello"
48 65 6c 6c 6f 00 73 20 6a 75 73 74 20 61 20 70 72 69 6e 74
69 6e 67 20 74 65 73 74 00 00 00 00 00 00 00 00 00 00 00 00
Notice the 00 on str[5]. That's how the print function will know how much it actually needs to send, despite the actual longitude of the vector and the whole content.
You are not answering the original question "what does the symbol mean". Please expand your answer to address the original question.
– Michal
Nov 8 at 20:28
Other answers already mention thatstr
is an array of size 7, including the accepted answer from seven years ago. Why repeat it yet again (without adding anything new)?
– melpomene
Nov 8 at 20:37
@Michal, you do realize the original post has 3 questions, right?
– L. Lopez
Nov 10 at 18:18
@melpomene. I do apologize for that. I expanded the answer and hopefully it clarifies further and adds more, as you seem to want.
– L. Lopez
Nov 10 at 18:20
add a comment |
up vote
0
down vote
up vote
0
down vote
char str= "Hello";
That would be 7 bytes.
In memory it'd be:
48 65 6C 6C 6F 00 00
H e l l o
Edit:
What does the symbol mean in a C string?
It's the "end" of a string. A null character. In memory, it's actually a Zero. Usually functions that handle char arrays look for this character, as this is the end of the message. I'll put an example at the end.What is the length of str array? (Answered before the edit part)
7and with how much 0s it is ending?
You array has two "spaces" with zero; str[5]=str[6]=''=0
Extra example:
Let's assume you have a function that prints the content of that text array.
You could define it as:
char str[40];
Now, you could change the content of that array (I won't get into details on how to), so that it contains the message: "This is just a printing test"
In memory, you should have something like:
54 68 69 73 20 69 73 20 6a 75 73 74 20 61 20 70 72 69 6e 74
69 6e 67 20 74 65 73 74 00 00 00 00 00 00 00 00 00 00 00 00
So you print that char array. And then you want a new message. Let's say just "Hello"
48 65 6c 6c 6f 00 73 20 6a 75 73 74 20 61 20 70 72 69 6e 74
69 6e 67 20 74 65 73 74 00 00 00 00 00 00 00 00 00 00 00 00
Notice the 00 on str[5]. That's how the print function will know how much it actually needs to send, despite the actual longitude of the vector and the whole content.
char str= "Hello";
That would be 7 bytes.
In memory it'd be:
48 65 6C 6C 6F 00 00
H e l l o
Edit:
What does the symbol mean in a C string?
It's the "end" of a string. A null character. In memory, it's actually a Zero. Usually functions that handle char arrays look for this character, as this is the end of the message. I'll put an example at the end.What is the length of str array? (Answered before the edit part)
7and with how much 0s it is ending?
You array has two "spaces" with zero; str[5]=str[6]=''=0
Extra example:
Let's assume you have a function that prints the content of that text array.
You could define it as:
char str[40];
Now, you could change the content of that array (I won't get into details on how to), so that it contains the message: "This is just a printing test"
In memory, you should have something like:
54 68 69 73 20 69 73 20 6a 75 73 74 20 61 20 70 72 69 6e 74
69 6e 67 20 74 65 73 74 00 00 00 00 00 00 00 00 00 00 00 00
So you print that char array. And then you want a new message. Let's say just "Hello"
48 65 6c 6c 6f 00 73 20 6a 75 73 74 20 61 20 70 72 69 6e 74
69 6e 67 20 74 65 73 74 00 00 00 00 00 00 00 00 00 00 00 00
Notice the 00 on str[5]. That's how the print function will know how much it actually needs to send, despite the actual longitude of the vector and the whole content.
edited Nov 10 at 18:25
answered Nov 8 at 20:23
L. Lopez
11
11
You are not answering the original question "what does the symbol mean". Please expand your answer to address the original question.
– Michal
Nov 8 at 20:28
Other answers already mention thatstr
is an array of size 7, including the accepted answer from seven years ago. Why repeat it yet again (without adding anything new)?
– melpomene
Nov 8 at 20:37
@Michal, you do realize the original post has 3 questions, right?
– L. Lopez
Nov 10 at 18:18
@melpomene. I do apologize for that. I expanded the answer and hopefully it clarifies further and adds more, as you seem to want.
– L. Lopez
Nov 10 at 18:20
add a comment |
You are not answering the original question "what does the symbol mean". Please expand your answer to address the original question.
– Michal
Nov 8 at 20:28
Other answers already mention thatstr
is an array of size 7, including the accepted answer from seven years ago. Why repeat it yet again (without adding anything new)?
– melpomene
Nov 8 at 20:37
@Michal, you do realize the original post has 3 questions, right?
– L. Lopez
Nov 10 at 18:18
@melpomene. I do apologize for that. I expanded the answer and hopefully it clarifies further and adds more, as you seem to want.
– L. Lopez
Nov 10 at 18:20
You are not answering the original question "what does the symbol mean". Please expand your answer to address the original question.
– Michal
Nov 8 at 20:28
You are not answering the original question "what does the symbol mean". Please expand your answer to address the original question.
– Michal
Nov 8 at 20:28
Other answers already mention that
str
is an array of size 7, including the accepted answer from seven years ago. Why repeat it yet again (without adding anything new)?– melpomene
Nov 8 at 20:37
Other answers already mention that
str
is an array of size 7, including the accepted answer from seven years ago. Why repeat it yet again (without adding anything new)?– melpomene
Nov 8 at 20:37
@Michal, you do realize the original post has 3 questions, right?
– L. Lopez
Nov 10 at 18:18
@Michal, you do realize the original post has 3 questions, right?
– L. Lopez
Nov 10 at 18:18
@melpomene. I do apologize for that. I expanded the answer and hopefully it clarifies further and adds more, as you seem to want.
– L. Lopez
Nov 10 at 18:20
@melpomene. I do apologize for that. I expanded the answer and hopefully it clarifies further and adds more, as you seem to want.
– L. Lopez
Nov 10 at 18:20
add a comment |
protected by melpomene Nov 8 at 20:35
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3
@CodyGray: Why have you removed the C++ tag? This has changed the correctness of some of the answers and subsequent comments?
– CB Bailey
Jan 17 '11 at 9:20
3
@CodyGray: C strings are still often used in C++. As for answers not being correct, that was my point; I downvoted an incorrect answer and you magically made it correct thus invalidating my downvote.
– CB Bailey
Jan 17 '11 at 9:27
2
@Charles Bailey I am mainly using C++, but of course I want to know is there any difference between C and C++ . That's why I add C++ tag.
– UmmaGumma
Jan 17 '11 at 9:38
2
@Ashot: Next time, please add that to your question. It's difficult to infer things like that from tags, and I'm really bad at reading people's minds. @Charles: Ultimately, I suppose, my aim was to reduce ambiguity. It seems you're arguing my side when you say the correctness of answers hinges on the tags in use. Like I said, feel free to rollback my edits if you disagree.
– Cody Gray♦
Jan 17 '11 at 9:41
3
@CodyGray: At one particular point in the cycle of edits an answer suggested that something like
char a[2] = "OK";
was OK. I immediately downvoted but as I was writing my comment I double checked the tags and noted that the question was now only about C.– CB Bailey
Jan 17 '11 at 9:52