Components of an ABAP Program

An ABAP program is more than just source text. The following components
belong to an ABAP program:
Source text
Contains the ABAP statements.
Program attributes
Contains (among other things) technical settings for program execution.
Screens
Screens consist of the actual screen contents and the associated flow logic.
Selection screens and lists are special kinds of screens, whose layout and
flow logic are designed exclusively using ABAP statements.
User interface
The user interface consists of all the individual user interface elements; It
is made up of titles and GUI statuses. In turn, GUI status is a collection
of function key settings and menus.
Text elements
Text elements are language-specific. They include selection texts, list
headers, and text symbols. All short texts and long texts can be translated.
Documentation
The documentation is also language-specific. You should always formulate
documentation from the user's perspective. If you want to document the
programming techniques you have used, use comments in the program code
instead.
Variants
Variants store predefined input fields on program selection screens.