Modulepool Program (Transaction Program)

GENERAL INTRODUCTION TO TRANSACTION

        Transaction, in R/3 system is an operation that lets the user make necessary changes to the database. The entire R/3 system is nothing but set of business transaction. The data transfer from old system to SAP R/3 database, or modifying data, or deleting data, which is not required, is done through transaction.

       For SAP system, Transaction is nothing but sequence of steps called as dialog steps and for user it is sequence of screens that appears one after the other depending upon the option he selects. The special transaction monitor called the SAP dispatcher handles the sequence of steps that takes place in any transaction. The main task of transaction is to update database table. The database table is not updated until a transaction is completed. All changes can be rolled back if the transaction has not finished.

The transaction contains two steps which are as following:

• Interactive phase: In this step, user enters the data, which needs to be inserted or deleted or modified on to the screen. There can be single screen or multiple screens depending upon the transaction. So this step can consist of single step or multiple steps. In this phase you prepare database record.

• Update phase: This phase processes the database record and updates the database table. Actual updating of database table takes place in this phase.

All the transactions are associated with transaction code. And all these codes are stored in a table TSTC.

Logical Unit of Work (LUW)

    The R/3 system is multi user system and many users access the same information at the same time, which is mainly DATA. Consider the case where one user is modifying a record, and second user is trying to delete the same record. If the second user is successful in deleting the record then the first user will face problem for modifying the record that is already deleted. The avoid such situation, R/3 system has provided Logical Unit of Work, which is defined as a locking mechanism to protect transaction integrity. Of course, there are other measures, which ensures data integrity like check table i.e. foreign key relationship. Within SAP system there are three types of transaction and may be distinguished as:

• Database transaction known as LUW. It can be defined as a period in which operation requested must be performed as a unit, i.e. all or nothing operation. At the end of LUW, either of the database changes are committed or rolled back.

• Update transaction or SAP LUW. One SAP LUW can have several databases LUW. So a set of a database is either committed or rolled back. The special ABAP/4 command COMMIT WORK, marks the end of a SAP LUW.

• ABAP/4 transaction. Is made up of a set of related task combined under one transaction code. ABAP/4 transactions are for programming environment, in which ABAP/4 transaction functions like one complete object containing screens, menus and transaction codes.

     R/3 system has provided in built locking mechanism, which defines the Logical Unit of Work. Also user can set his own locking mechanism. The LUW starts when a lock entry in the system table is created, and it ends when the lock is released.

     To provide the user the facility to communicate with the table in order to modify or delete or insert data, R/3 has provided tool called SCREEN PAINTER. This tool allows you to design screen, process screen through program and update the database table. SAP has provided one and only one way to update the database table, i.e. transaction. Though you can update database table by using open SQL statement through program, SAP usually doesn’t recommend this kind of updating. Many standard transactions are available to update standard table but if the need arises, the developer should be able to develop new transaction, which allows the updating of database tables. This can be achieved by using various components of screen painter.

Following are the few concepts and steps for creating entire new transaction.

Dynpro concept

A dynpro refers to the screen + flow logic. With screen painter you can develop screen and flow logic. The relationship between screen, flow logic, and program can be shown as follows:

Dynpro, as figure indicates consist of screen and flow logic and places exactly one call to module pool program. A transaction consists of many screens and for each screen flow logic is attached. When the transaction is executed, the screen places a call to flow logic and flow logic in turn places a call to module pool program.

·                     A module program is usual ABAP/4 program that consist of modules and data declaration.

·                     ABAP/4 is an event driven language. In module pool program too, events get triggered and these events are handled in flow logic. Flow logic editor is subset of ABAP/4 editor. The system automatically displays the two important events for the flow logic.

·                     Screen is the important component of dynpro and can be created, designed by screen painter.

        Screen Painter

A screen painter can be started by

Development workbench  Screen Painter

Or SE51 transaction code.

       Using Screen painter

           The process of creating a dynpro includes the creation and definition of all the needed screen components.

           The steps involved in creating the dynpro are as follows:

• Create screen and attributes by using screen attribute screen.

• Select and place the needed fields within the screen by using dict/program fields.

• Establish the field attributes to which the screen belongs by using field list.

• Define the flow logic respect to the transaction to which it belongs by using flow logic.

Creating a new Screen

Steps involved are as follows:


• Enter the name of program and number of the screen

• Click on Create

• On “screen attribute” screen enter short description

• Enter screen type. Normally, you select NORMAL option for usual R/3 screen. Other options available are SUBSCREEN & MODAL DIALOG BOX. Modal dialog box is used to establish independent and interactive dialog box while subscreen is screen within screen.

• Next attribute to be passed is NEXT SCREEN. Here you need to specify the next screen number, which must be processed after the current one.

Designing of Screen

Screen can be designed by using FULL SCREEN EDITOR. You can go to full screen editor.

From screen attribute screen

By pressing full screen editor pushbutton

Or From initial screen of screen painter.
There are two modes available with full screen editor.
• Graphical mode. The graphical mode works similarly to typical window application.

• Alphanumeric mode (rarely used).

Elements of screen

  • Text – Standard text or field labels.

• Entry - display field.

• Radiobutton – All radiobutton must be associated with one group.

• Checkbox – Normally used for YES/NO operations.

• Pushbutton – Used for activating particular function.

• Boxes – grouping together many screen elements.

• Subscreens – This is a screen area in which you can display another screen.

• Table controls – This area of screen is similar to table but should be treated as a loop.

• Status - Display output fields containing icon.
All these elements are on the control bar of full screen editor and can be placed on the screen work area by clicking and placing them wherever needed.

Selecting Screen fields

Screen field can be either dictionary objects or program fields. Steps involved in the placing of fields on the screen are as follows:

Click the pushbutton Dict/program fields on the full screen editor


Or Goto  dict/prog fields.

• Enter table name.

• Click Get from dictionary.

• Select fields.

• Click copy pushbutton.

• Position the cursor where you want those fields to be placed.

To adjust various screen elements, you can use drag and drop facility for screen elements.

 

Attributes of Screen Elements

 

The entire element of a screen has some attributes, which determines their behavior.

  • General – These attributes are directly managed by the screen painter like name of the element, or text of element or column width and various things associated with the screen.

• Dictionary – These attributes are applicable to fields, which are from dictionary. Various components of dictionary can be attached to this element like search help, foreign key.

• Program.

• Display – Behavior of the element with respect to their display feature.

Attribute dialog box can be displayed by
• Clicking on the ATTRIBUTE push button on the application tool bar.

• Double clicking on the element.

Field List

 

This list displays a list of all screen elements together with their screen attributes.  One important element of Field list is OKCODE. Any pushbutton is associated with function code as in menu item in menu painter. When the user clicks the pushbutton this code is stored in OKCODE. This OKCODE is created by system without a name and is not visible on the screen. In ABAP/4 this field is work field and is nothing but an area wherein system stores the variable and is the last field of the field list and is invisible, hence user needs to give the name OKCODE. It is not mandatory to give the name OKCODE; developer can give any name to this field.

 

Screen Flow Logic

You can go to this screen either by

Initial screen of Screen painter  Flow logic

Or  From Screen attribute screen  Flow logic

When transaction is executed, the screen is displayed, user enters few fields, selects few functions. Later the screen is processed and processing of screen is done by flow logic.    The events that are associated with screen are as follows:

• Process before Output (PBO)

• Process after input (PAI)

• Process on value request (POV)

• Process on help request (POH)

The system automatically displays two very important events or modules in flow logic i.e. PAI and PBO

PBO event

This event is triggered before the screen is displayed. The processing of screen before the display of screen is done in this event. For example, filling in default values in the screen fields. 

PAI event

This event is responsible for processing of screen after the user enters the data and clicks the pushbutton. The processing of screen can include displaying another screen, or just displaying list or quitting the transaction itself and many more things. Usually it is displaying another screen. These operations can be carried out in the PAI event. OKCODE plays an important role in this operation.

POV event

Process on value request is triggered when the user clicks F4 key. You can handle this event when the user presses F4 key by writing code for the same in module pool program. Normally when the user presses F4, list of possible values is displayed.  The standard list produced by system is adequate for applications you develop yourself.  However, you can also have the option of setting up your own documentation and lists of possible values that are more detailed.

POH event

Normally when the user places the cursor on the field and presses F1 function key, the system displays its own Help for that particular field. You can add your own functionality to the Help button by writing code for the same in the POH event.

Module Pool Programming

This component though is not attached to the screen painter, plays important role in transaction. Normally, for reports, on line executable programs are written but for transaction, Module Pool Programs are written. The module pool program contains only modules to handle various events associated with screen and data declaration statements.

System divides the module pool program into several include program. These are global field, PBO modules, and PAI modules. It is entirely user’s decision whether to use these modules or write directly into main program.

Creation of Module Pool Program

You can create module pool program either through


Object browser

System automatically creates the module pool program and for these program which are created through object browser, system creates the include modules.

Or ABAP/4 editor

It is similar to normal program creation. Type of program should be given ‘M’ and is not created by system.

Communication between Dynpro and Module Program

For each screen, the system executes the flow logic, which contains corresponding events. The control is passed to Module Pool Program. Module Pool Program handles the code for these events and again passes back control to the flow logic and finally to screen. Unlike on line program, in this case, the control remains with flow logic. The switching of control between flow logic and module pool program and back is common process when user executes transaction.

Creation of a Complete Transaction

Steps involved to create a complete transaction

• Create module pool program.

• From screen painter create screens.

• Write flow logic for each screen.

• Write code for all the events in module pool program.

• Check for any error in screen and flow logic.

• Generate each and every component of screen i.e. flow logic and screen.

• Single screen can be tested using Screen Painter.

• Create transaction code through object browser.

• Generate the transaction code.

• User can execute the transaction by entering the transaction code in the command field.

Handling Function Code

  The function code or OKCODE is the last field of Field list. Function code can be handled as follows:

During the Designing of the screen, a function code is assigned to pushbutton.

• In field list, developer needs to specify OKCODE as last field.

• In module program it is a global field and can be evaluated in the PAI event.

• A function code is treated in the same way, regardless it comes from pushbutton, menu item or any other GUI element.

A complete example for transaction is shown below:

If you have a screen like the one below:

When the user clicks on the Display button, you want to display details of sflight, with corresponding carrid and connid (which is entered by the user).

Module pool program to handle this particular screen is as follows:
Program YVTEST7.


TABLES: SFLIGHT.

DATA: OKCODE (4).
MODULE INPUT1 INPUT,

CASE OKCODE.

WHEN ‘DISP’.

SELECT * FROM SFLIGHT

WHERE CARRID = SFLIGHT – CARRID AND

CONNID = SFLIGHT – CONNID.

ENDSELECT.

LEAVE TO SCREEN 200.

WHEN ‘EXIT’. LEAVE TO SCREEN 0.

ENDCASE.

ENDMODULE. “INPUT1 INPUT

MODULE USER_COMMAND_0200 INPUT.

CASE OKCODE.

WHEN ‘BACK’. LEAVE TO SCREEN 100.

ENDCASE.

ENDMODULE. “USER_COMMAND_0200 INPUT


When the user clicks on display, control is transferred to screen no. 200 on which you display sflight details & on the same screen, when user clicks on BACK button, he comes back to main screen.


Flow logic for screen 100 is as follows:

PROCESS AFTER INPUT.

MODULE INPUT.

Flow logic for screen 200
PROCESS AFTER INPUT.

USER_COMMAND_0200.


MODULES: Modules are handled in module pool program.

You need to write flow logic for screen 200 and design screen 200.

In case of transaction transfer of data from program to screen is automatic i.e. you need not transfer the data from program to screen explicitly. The fields, which you define in the screen receives the data from program and displays the same.

The Field Checks

As already mentioned Transaction is the only method, which SAP recommends to update the database tables. Data entered in the database table should be valid and correct. Data entered is validated at each and every point. ABAP/4 offers various methods to validate data and those are as follows:
• Automatic field checks

• Checks performed in the flow logic

• Checks performed in the ABAP/4 module pool program

Automatic Field Checks

  These checks are based on the field information stored in the dictionary. These checks are performed by the system automatically when the user enters the data for the screen field. System performs these checks before PAI event is triggered. Types of field checks performed by system are as follows:

• Required input

While designing the screen, for particular screen field if you click the Req. Entry checkbox, the field becomes mandatory. When the transaction is executed if user leaves this particular field blank, the system displays error message. User cannot proceed until the user enters some data.

• Proper Data Format

Each field has its own data format whether it is table field or screen field. Whenever data is entered, system checks for the proper format of the data. For example date. Each user has its own format for date, which is defined in the user master record. If the date defined in the user master record is in the format DD/MM/YYYY, if the user enters the date, say, in YY/DD/MM, the user displays the error message. System also checks for the value of month or days. For example if month entered is greater than twelve then the error message is displayed.

• Valid Value for the Field

In data dictionary two tables are related by Primary key-Foreign key relationship. Whenever the user enters the data, the system checks for the check table values. Also in Domain, if you have fixed values, then the system checks for these values.

Automatic field checks are repeated each time the user enters the data.

 

Flow Logic Validations

  Consider the case where you want user to enter only ‘LH’ and ‘SQ’ for sflight-carrid. In this case, you are restricting value of a screen field. This cannot be achieved by automatic field check. Hence there is a need of additional validation. It can be done in flow logic by using following statement:
Field --------------- Values

Syntax

PAI.

Field sflight-carrid values (‘LH’).
For multiple values

PAI.

Field sflight-carrid values (‘LH’ ‘SQ’).

Field sflight-price values (between 1000 and 2000).

In this case when the user enters the value, PAI is triggered and field is checked for that particular value. If the value entered happens to be wrong, that field is enabled for user to enter. If you have multiple Field statements in your flow logic, it is sequential execution.
Consider the following case:

PAI.

Module  assign.

  Field sflight-carrid values (‘LH’ ‘SQ’).
In ABAP/4

Module assign.

Data: carrid1 like sflight-carrid.

Carrid1 = sflight-carrid.

Endmodule.

In this case, Sflight-carrid is used in the flow logic before the field statement. The system will give invalid value or some previous value as the field sflight-carrid is used in module before it is checked i.e., field statement is after the module in which sflight-carrid is being used. The field is not available to the system unless it executes the field statement. Field statement transfers the values to the program and is done only once. If you don’t have Field statement in your flow logic, transfer of values takes place in PAI event.

Consider one more case where you have multiple field statement.

  PAI.

Field Sflight-carrid values (‘LH’).

Field Sflight-connid values (‘0400’ ‘0500’).

In this case if the user enters only carrid wrong, then this particular field is enabled and rest of the fields are disabled for user to input. Many times if the user enters wrong value for one field, then you might want to give option to user to enter all the fields, which is not possible by using Field statement only. This functionality can be achieved by Chain – endchain.

  Syntax

Chain.

Field sflight-carrid value (‘LH’).

Field sflight-connid values (between ‘200’ and ‘500’).

Endchain.

Field sflight-price values (‘100’ ‘1000’).

In this case, if the user enters wrong value only for carrid, both the fields i.e. carrid and connid are enabled as they are grouped together in the Chain statement. The field price will be disabled for input. Usually, logically related fields are grouped together with Chain-Endchain statement.

Module Pool Program Validations

Checking fields ABAP/4 program includes
• Field statement in flow logic.

• Module statement in ABAP/4 module pool Program.

Syntax

PAI.

Field sflight-carrid module .

This module can be handled in the main program i.e. module pool program.

In ABAP/4 program

Module Check.

Select single * from sflight where carrid = sflight-carrid.

If sy-subrc ne 0.

Message e001.

Endif.

In this case, field sflight-carrid is checked in the table for its existence.

Dynamically Calling the Screens

About Displaying Next Screen

Transaction is a sequence of screens, which are displayed one after the other. The next screen displayed depends upon the attributes of first screen. In attributes you need to give Next Screen number i.e. if next screen displayed should be 200 screen, then this number should be given in next Screen attributes. These are static attributes of the screen. By default, if nothing is specified in the program, the system branches out to the screen number, which is specified in the attribute screen.
But this doesn’t happen always. If you have many pushbuttons on the screen like the one in the following case:

In this case, if user selects MARA pushbutton, then fields from Mara table are displayed. When the user clicks on the MARD, then the fields from MARD table are displayed. Depending upon users selection, the screen is branched out and this has to be done during runtime. This functionality can be achieved by dynamically calling the screen in module pool program.

  The screen can branch out to new screen depending upon user selection. Following command in module pool program can do this:

• SET SCREEM

• CALL SCREEN

• LEAVE TO SCREEN

All these commands override the specifications given in the attributes. This overriding is temporary. The values stored in the attribute are not changed.

Set Screen

  Syntax
Set screen .

In module pool program

Case okcode.

When ‘DISP’.

Set screen 200.

When ‘LIST’.

Set screen 300.

Endcase.
In this case, the entire processing of current screen takes place and then the system branches out to next screen. If you want to branch out to the next screen without processing the current screen, LEAVE SCREEN should be used along with the SET SCREEN.
For Example:

Case okcode..

         When ‘DISP’.

                Set screen 200.

                Leave Screen.

       When ‘LIST’.


             Set screen 300.

             Leave Screen.

Endcase.

When SET SCREEN is used, control cannot be transferred to the main screen or previous screen, unless you write code for the same.

Call Screen

  Usually used for pop up screens. Many times, there is a need for user to enter additional information or secondary information on another screen or pop up screen. Once the user enters the data, he should be able to go back to main screen or to the screen where he started. This is not possible by using SET SCREEN. CALL SCREEN achieves this functionality.
Syntax

Call Screen 200.

Will simply call a screen number 200 from a main screen. Once the screen is displayed the user can enter all the data and return to the main screen by clicking BACK button.
To call screen as pop up screen the syntax is

Call screen starting at

Ending at .
In this case window will be popped as window and user can close it by using BACK button.

Leave to screen

  To SET a new screen without processing current screen, you need to use the following two statements together:
SET SCREEN 200.

LEAVE SCREEN.

Or a Single statement

LEAVE TO SCREEN 200.

Table Controls

  A table can be created in transaction. These tables when designed on the screen are called as SCREEN TABLES. These screen tables are of two types viz.

• Table controls

• Step loops

Though these are tables when code is written to handle them, the tables are treated as loops.

Features of Table Controls

  • Data is displayed in the form of table when many records match the criteria.

• Table control gives user the feeling of an actual table.

• You can scroll through the table vertically and horizontally.

• You can select rows and columns

• Resize the width of a column

• You can have separator lines in between rows and columns

• Automatic resizing of the table when the user resizes the window.


In general table control includes all the features of an actual table and user gets the feeling that he is actually working with table. You can update information in table control and it can be updated in the database table by writing code for it.
Steps associated for creating complete screen table are as follows:

• Declaration of table control in module pool program.

• Designing of table control on the screen.

• Passing data to table in flow logic.

Declaring of Table Control in the Module Pool Program

Syntax

Controls TCI type Tableview using screen


When you use table control in a screen you must declare the structure in module pool program. Important fields of tableview are as follows:
• Lines – number of displayable rows in a table.

• Top_line – the row of table where the screen displays start.

• Current_line – The row currently being processed inside a loop.

When you process the table control in flow logic depending upon where you want to start display of rows, you need to use these variables

Designing Table Control on Screen

• To design table control on the screen, you need to click on Table in control bar and place it on the screen. You can adjust the length and width of table control.

• Name the table control. (Here you need to use same name which you have used for declaration of table control in module pool program)

• From dictionary object, select table fields and place them in the table control.

Passing data to table Control

  As already mentioned, table controls are tables but are treated like loops. Usually transfer of data from program to screen is automatic. But in case of table control, transfer of data is not automatic. You need to explicitly transfer the data to table control. ABAP/4 provides loop statement, which is associated with flow logic to transfer the data. Because table control is treated like a loop, data from where it is transferred should be a loop. You cannot transfer the data by only select statement; you need to put the data into internal table. ABAP/4 provides the LOOP statement, which is associated with the flow logic and allows you to loop through the table control and internal tables. In between LOOP-ENDLOOP, you can use most of the flow logic keywords like field values. Module etc.
You need to code a LOOP statement in both PBO and PAI event of the screen. With LOOP statement, you can transfer the data from program to table control and vice versa. That is, if user updates the value in the table control, you can update database table with its value. And this can be done in PAI event. So even if you are not updating database table through the table control, you need to put the LOOP statement in the PAI event also.

 Syntax

PBO.

LOOP AT with control cursor

PAI.

Loop at itab.

Proper usage of Table Control is as follows:

In flow logic.

PBO.


LOOP AT ITAB WITH CONTROL TC1 CURSOR TC1-TOP_LINE.

MODULE ASSIGN.

ENDLOOP.
PAI.

LOOP AT ITAB.

ENDLOOP.

Considering, we have following fields in table control and the screen looks like this:

 

In module pool program

  CONTROL TC1 Type tableview using screen 200.

Module assign.

   Sflight – carrid = itab – carrid.

   Sflight - connid= itab - connid.

   Sflight - fldate= itab – fldate.

Endmodule.

The transfer of the data from program to table control takes place in steps and these steps are as follows:

• With LOOP AT statement the first row is picked up and placed in the header of the internal table.

• Whatever statements you have in between LOOP-ENDLOOP are executed. In this case, you have Module statement. In Module statement, value of internal table is assigned to table control field.

• The row in internal table is transferred to the first line of the table control as stated in the LOOP AT statement.

• The system encounters the ENDLOOP statement and Control is passed to the next line of the internal table.

• In the same way, all the records of the internal table are passed to the table control.

STEP LOOPS

Step Loops are type of screen table as already mentioned. Step loops are repeated blocks of field in a screen. Each block contains one or more fields and these blocks are repeated. Step loops aren’t like actual table. You can scroll vertically but not horizontally. Three steps are associated with creation of step loops:
• Creation of step loops on screen, which includes declaring fields on the screen and then defining the step, loops for these fields.

• Passing data to the step loop is exactly similar to the passing of data to table controls.

• In step loop, you don’t need to define the step loop as such in the module pool program but the cursor needs to be defined in the program.

Types of Step Loops

• Static – Static Step Loop (SSL) have fixed size that cannot be changed during the runtime. If user resizes the window, the size of the static step loop is not changed.

• Dynamic – Dynamic Step Loop (DSL) is variable in size. When the user resizes the window, the system increases or decreases the number of the step loop blocks.
You can have only one dynamic step loop and can have as many static loops in your transaction.

Programming with the Static and dynamic step loop is exactly same.  For the system or for the user it doesn’t make any difference whether it is static or dynamic step loop.  Only attribute, which you fix during designing of the step loop, is type attribute for step loop F for fixed i.e static and V for variable i.e. dynamic.

  Writing code for Step Loop in the flow logic.

PBO.

    Loop at itab cursor cl.

    Module set.

    Endloop.

PAI.

   Loop at itab.

   Endloop.

* Empty loop is must for both table control and step loop

LOOP AT statement for step loops and Table controls is similar. Loop At statement transfers the data to screen table. You need to have the Module to assign the values for the screen table.
In module pool program you need to define the cursor.

Date: CL TYPE i.

* Cursor parameter tells which line of step loop display should start.

“Module Set” in module pool program assigns the values to step loop fields, which is similar to table controls.

Branching to List Processing

Switching To List Mode

  You can display a list within a transaction.

You can produce a list from module pool program by using the command

Leave to List-Processing.
This statement switches the system from dialog mode to list mode. And from this point onwards until you return to dialog mode, you can use all the normal report statement like write, select or any other event

Returning back from LIST mode

  You can return back to dialog mode by clicking the BACK button.

You can have your GUI status and write code for the same. You can include the command LEAVE LIST-PROCESSING. When the system reaches this command, it leaves the list mode and returns to the dialog mode.

Help & Value Request

  In any transaction, When the user presses F1 or ? on a field, System provides the help facility for that particular field. In dialog program, when F1 is pressed, help provided by R3 system is sourced from data element documentation. If this documentation is not present for that particular field or if user needs to display additional information for that particular field, then user defined help can be provided through PROCESS ON HELP REQUEST.
In ABVP/4 help can be provided to the user by:
Data element documentation: The F1 help can be enhanced, by adding an additional text for the data element in ABAP/4 dictionary.

It can be done with the help of following steps:

Place cursor on the screen field,

GOTO  DOCUMENTATION  DATA ELEMENT DOCUMENT

You can now extend the existing help.

USING THE PROCESS ON HELP-REQUEST.

If you don’t have this event in a program, then the documentation of the field in the ABAP/4 dictionary is taken into consideration. If this event exits in the program then it is executed.

Process on HELP-REQUEST event

  This event is triggered when user presses F1 on a screen field. You need to handle this event in flow-logic by specifying the fields and attaching the module to it.
Syntax

PROCESS ON HELP –REQUEST.

FIELD SFLIGHT-CARRID MODULE HELP-FOR-CARRID.

In module pool program

MODULE HELP.

Write : `This is field is from sflight table’

Write : / ‘It is of four Character’.

ENDMODULE.

Value Request

When the user presses F1 on this particular field, then this message will be displayed on the screen.  Whenever the user presses F4 on the screen field list of possible values, particular fields are displayed. If the standard value-help is inadequate or if you want to display additional fields or with different combination of fields, developer can program this in PROCESS ON VALUE-REQUEST event in the flow-logic and subsequent module in the module pool program. When the user presses F4, list of possible values are displayed either from matchcode objects or check table or help view or domain. Each one of them is explained briefly.

Check Table: If a check table is assigned to the table field and if the user presses F4 for that particular field, then all the key fields are displayed.

Domain Values: The values defined in the domain are displayed. These values are set in domain when the domain is created in the dictionary.

Help views:  In cases where the check table is not sufficient, you can create a help view with this check table, which gives additional information like explanatory text for the fields of the check table.

Changing The Screen During Runtime

The attributes are assigned to the screen field when the screen is designed in full screen editor. Such kind of assignment is static, which means that these attributes are fixed. But many times the need to change the attributes of the screen arises. And this has to be done during runtime.

Need To Change Screen

There can be a requirement in the transaction that, certain fields on the screen

Appear only in certain conditions.

Are in Change/display mode according to user inputs

Become mandatory subject to specific inputs.

Changes its format depending upon certain conditions.

Modifying the screen

At the runtime, attributes for each screen field is stored in system defined internal table, with header line, called as SCREEN TABLE. It contains name of field and its attributes. This tab le can be modified during the runtime i.e. through module pool program.