How is the following code evaluated in C? -

#include <stdio.h>  int main() {     char *p="hello";     char *p1;     p1=p;     while(*p1!='\0')         ++*p1++;      printf("%s\t%s",p,p1); }

what should output be? how code evaluated? should output ifmmp or runtime error?

you invoking undefined behavior, modify string literal within main's body:

char *p = "hello"; char *p1;  p1 = p; while (*p1 != '\0')     ++*p1++; // undefined behavior

the following statement:

++*p1++;

is same as:

++(*(p1++));

it can written 2 statements:

++(*p1);  // increase *p1 1 p1++;     // increase p1 1

if want output ifmmp (i.e. every letter replaced next one), change:

char *p = "hello";

with:

char p[] = "hello";

Brant