In this lesson, you add a function to the text editor that allows you to write-protect text lines in the editor window.

Optimizing the number of flush calls simply means that you should build as few flush calls as possible into your programs. However, this implies that you must know at which points in your program synchronization is absolutely essential.

In the exercises, we therefore present the 'simple' solution first, discuss it with regard to the flush issue and make suggestions for improvement. If you are aware of the consequences of applying the "as few flush calls as possible" rule, then you can reduce their number.

In this lesson, you learn:

• In which cases errors might occur if flush calls are used wrongly
• How to reduce the number of flush calls
• How the actual parameters of control methods are handled implicitly.