Why strcmp equals zero

I followed Hammer's tutorial on Comparing Strings, but one thing I don't understand.

Code:

---


if(strcmp(foo, bar) == 0)
  puts("Strings equal");
else
 puts("Strings not equal");

---

Why compare these strings to zero. I know that in boolean 0 is false and 1 is true. I have to say that these tutorials are very good for beginners.

Thanks.

string comparison starts with the first character and goes on till a character differs or one of the strings gets completed
coonsider strcmp(s1,s2)
if strcmp(s1,s2) == 0 => s1==s2
if strcmp(s1,s2) <0 => s1<s2
ifstrcmp(s1,s2) > 0 => s1>s2

oh and the value strcmp returns is the diff. betwn. the value of the corres. characters of the strings. //pls. verify this

Somehow I got the code for this (and many other c functions)

-edit-
Ok, they're all the source code for C functions....in C. Some of the functions are written in assembly, but I don't feel like finding the one's I've seen. It's just nice to see how they did the actual functions written out.

anyways

Code:

---

   
    /***
    *strcmp - compare two strings, returning less than, equal to, or greater than
    *
    *Purpose:
    *          STRCMP compares two strings and returns an integer
    *          to indicate whether the first is less than the second, the two are
    *          equal, or whether the first is greater than the second.
    *
    *          Comparison is done byte by byte on an UNSIGNED basis, which is to
    *          say that Null (0) is less than any other character (1-255).
    *
    *Entry:
    *          const char * src - string for left-hand side of comparison
    *          const char * dst - string for right-hand side of comparison
    *
    *Exit:
    *          returns -1 if src <  dst
    *          returns  0 if src == dst
    *          returns +1 if src >  dst
    *
    *Exceptions:
    *
    *******************************************************************************/
   
    int __cdecl strcmp (
                    const char * src,
                    const char * dst
                    )
    {
                    int ret = 0 ;
   
                while( ! (ret = *(unsigned char *)src - *(unsigned char *)dst) && *dst)
                                    ++src, ++dst;
   
                    if ( ret < 0 )
                                    ret = -1 ;
                    else if ( ret > 0 )
                                    ret = 1 ;
   
                    return( ret );
    }

---

To reiterate what alvarorahul said:

strcmp() compares the strings one character at a time. If the characters match it goes on to the next character. Once it finds a difference it subtracts the character from string2 from the character from string1.

So given:

Code:

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char s1[] = "My name is Bob";
char s2[] = "My name is Billy";

---

It will compare "My name is B" from both strings and then read o from s1 and i from s2 and then returns the value of o-i. If the value returned is < 0 then s1 is less than s2, if the value returned is > 0 then s1 is greater then s2. So by default (only range left) 0 means they are the same.

strcmp is really helpful in sorting algorithms.