Answer: you should use the Remove function.
Here is C example to remove first three characters from a string with C?
void chopN(char *str, size_t n)
{ assert(n != 0 && str != 0);
size_t len = strlen(str);
if (n > len)
return; // Or: n = len;
memmove(str, str+n, len - n + 1);