[SOLVED]Segmentation fault when using pointer in Function!

Question

I'm trying to write a function in C to converts all small characters in a string to upper case characters and returns the number of changed characters;

When I run it, I got a Segmentation fault. Can somebody helps me figure out what's wrong with my code ?? Thanks a lot.

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#include <stdio.h>

int str2upper(char *s){
int count=0;
int x;

for (x=0; s[x]!= '\0';x++){

if(s[x]>='a' && s[x]<='z'){
s[x]=s[x] -32;
count++;
}

}
return count;
}

int main()
{
printf("------------------------\n");

printf("%d", str2upper("aBCd") );
}

Answer 1

In main function:

char s[] = "aBcD";
printf("%d\n", str2upper(s));

You are passing a C-string literal, which is a constant char* (read-only memory address). Pass a char array which is readable & writable to the function.

Answer 2

Thank you. It works now! :D