arrays - Pointer and String Outputs in C -

i trying understand why following piece of code produces output of bcd123 123.

void f(char *p) {     *p += 1; }  int main() {     int i;     char a[] = "abc" "123";     char *p = a;      (i = 0; < 3; i++)         f(p++);      printf("%s ", a);      printf("%s ", p);      return 0; } 

void f(char *p) {     *p += 1; } 

adds 1 character passed in. 'a' + 1 = 'b' etc. in ascii table http://www.asciitable.com/

part 2

   char a[] = "abc" "123"; // same     char a[] = "abc123";       (i = 0; < 3; i++)             f(p++); <<<<===== moves p along string 3 places (once each loop)          printf("%s ", a);          printf("%s ", p);  <<< p points @ 4th char