fixed pezy#17

ch04/README.md

@@ -359,7 +359,7 @@ char cval; int ival; unsigned int ui; float fval; double dval;
 identify the implicit type conversions, if any, taking place:
 ```cpp
 cval = 'a' + 3; // 'a' promoted to int, then the result of ('a' + 3)(int) converted to char.
-fval = ui - ival * 1.0; // ival promoted to double, ui also promoted to double. then that double converted to float.
+fval = ui - ival * 1.0; // ival converted to double , ui also converted to double. then that double converted(by truncation) to float.
 dval = ui * fval; // ui promoted to float. then that float converted to double.
 cval = ival + fval + dval;  // ival converted to float, then that float and fval converted to double. At last, that double converted to char(by truncation).
 ```