#include <stdio.h>

char *string;


int main(void)
{
printf("Enter a string: ");
scanf("%sn",string);
putchar(*string);

int i;
for (i=0; i<3;i++)
{
  string--;
}
putchar(*string);

}

char string[1024];

putchar(string[i]);

char *str = string;

for (i = 0; i < 3; i++)
    str++;

putchar(*str);

str += 3;

putchar(*(str+3));

if (scanf("%1023s", string) != 1)
    ...something went wrong — probably EOF without any data...