c - Why does my code print the whole string multiple times rather than 1 time? -

i'm new c. i'm having trouble understanding fundamental materials in reading input , pointers. want use nextchar() function read , print each character of string enter in command line. try typing "hello"..it displays "hello" 6 times. can tell me why happens? how can fix it? thank time!

#include <stdio.h> #include <assert.h> char nextchar(char* ptr) {     static int = -1;     char c;     ++i;     c = *(s+i);     if ( c == '\0' )         return '\0';     else         return c; }  void display(char* ptr) {     assert(ptr != 0);          {         printf("%s", ptr);      } while (nextchar(ptr)); }   int main(int argc, const char * argv[]) {     char* ptr=argv[1];      display(ptr);     return 0; } 

the nextchar function reduced:

char nextchar(char* ptr) {     static int = 0;     i++;     return (*(ptr+i)); } 

and display to

void display(char* ptr) {     assert(ptr != 0);     char c = *ptr;          {         printf("%c", c);      } while (c = nextchar(ptr)); }