_CP_data is equivalent to the data string BASIC statement.
int _CP_data(CPSTR* string)
This function returns -1 if an error occurs. The error code is contained in _CP_errno.
/* Copies the "xx" item in the md to item "yy". */
CPSTR * s = _CP_mkstr("copy md xx");
CPSTR * t = _CP_mkstr("yy");
CPSTR * c = _CP_str_null;
CPSTR * r = _CP_str_null;
_CP_data(t);
_CP_execute(_CP_EXECUTE,s,&c,&r);