Note: you can always invoke Code completion using Ctrl + Space.

Another example includes the following situation:
If you have defined several string variables and several integer variables in your unit, when you start a command like "Form1.Caption:=" and hit Ctrl + Space, a list of arguments that are valid for the assignment is displayed. The list will contain (among others) string variables which you have defined, but not the integer ones.

When the code completion list is displayed, you can hold down the Ctrl key and click on any identifier in the list to browse to its declaration (if you have the sources of Borland Delphi units, you can see "inside" Delphi). Also, in the Code editor, if you hover the mouse pointer over the identifier, a hint window tells where it is declared. You can press Ctrl, point to the identifier in the code and click to move to its declaration.

"Unable to invoke Code Completion due to errors in source code"?
Uops, the code completion does not work! Now what?
The message 'Unable to invoke Code Completion' usually indicates some type of syntax error in your code. It can also indicate that you have not defined the method you are working in. Almost always the problem does exist but you might try recompiling the entire project to see if syntax errors do exist.

Code Templates

Another great example includes pressing Ctrl+J on a blank line, typing f, and double-clicking the selected function declaration - the function skeleton code will be inserted automatically at the current cursor position.

Code Parameters

Tooltip symbol insight, Tooltip expression evaluation
Great debugging tool. To test expression evaluation while the program is running "under" IDE, you stop the compiler (enter debug), and you can view the value of a variable by pointing to it with your cursor.
Symbol insight feature displays declaration information for any identifier by passing the mouse over it in the Code editor.

Class Completion

...
 public
  property MyProp : integer read fProp write SetProp;  CTRL + SHIFT + C
...

When complete hit Ctrl + Shift + C, Delphi automatically adds private read and write specifiers to the declarations, then adds skeleton code in the implementation section. This is what gets added by Delphi:

...
 private
  fProp: integer;
  procedure SetProp(const Value: integer)
...
 //implementation
...
procedure TForm1.SetProp(const Value: integer);
begin
  fProp := Value;
end;

Code Insight Settings

Note that all the Code Insight tools have lot more usage ways. The list can be found on Delphi Help under "Code Insight" when you click Help in the above dialog.

Some exercises for you...

   To the next chapter: A Beginner's Guide to Delphi Programming
This is the end of the thirteenth chapter, in the next chapter, we'll deal with ... well I don't know yet...

If you need any kind of help at this point, please post to the Delphi Programming Forum where all the questions are answered and beginners are treated as experts.