how to use comments in ABAP programming

Comments

Among your ABAP codes you can add comments by using two methods :
One is starting the line with an asterisk (*). The asterisk which is placed at the beginning of the line will indicate that all of the contens of the line are comment in content.
Second method is using double quotation mark (") in any place of a line. Double quotation mark will indicate that following content is comment.

You must start all your ABAP programs either with PROGRAM or REPORT statement.
REPORT should be used for ABAP reports programs whose output is a list.
PROGRAM can be used for all or for general ABAP programs.

All your ABAP programs should be assigned to a package. But you can define your ABAP programs as local or private objects instead of assigning them to a package.
Assigning to packages is requirement for SAPs Correction and Transport System.
While creating a ABAP program application, title and type attributes are must.

Below is a very simple ABAP report code which is showing variable declaration and value assigment to variables in the ABAP program.
Also you can see how variables are displayed in ABAP programming.