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Overview
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SAP R/3 logon Screen....................................................................6 Logging Off..................................................................................8 Using Transaction Code.................................................................8 Getting help in the R/3 system.....................................................10 Working with R/3 user sessions...................................................11 R/3 ARCHITECTURE
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Client / Server architecture..........................................................12 Three tier architecture of R/3.......................................................13 ABAP/4 DEVELOPMENT WORKBENCH
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DATA DICTIONARY
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About Data Dictionary.................................................................16 Advantages................................................................................16 Tables in ABAP/4 dictionary.........................................................19 Creation of table.........................................................................20 Creating Domain.........................................................................20 Creating Data Element................................................................20 GENERAL INTRODUCTION TO ABAP/4
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Characteristics of the ABAP/4 programming languages.................23 REPORTS....................................................................................23 DIALOG PROGRAMS.....................................................................24 2
ABAP BASICS DATA TYPES AND DATA OBJECTS
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Data Types.................................................................................26 Data Objects............................................................................... 27 Kinds of Data Objects..................................................................27 Parameters................................................................................. 29 WRITE STATEMENT
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Formatting output......................................................................32 Formatting options for all data types...........................................33 Formatting options for numeric fields..........................................33 BRANCHES
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Branching with IF statement........................................................35 Branching with CASE statement...................................................36 LOOPING
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Looping with DO statement.........................................................37 Looping with WHILE Statement....................................................37 TRANSLATE command.................................................................40 Insert statement.........................................................................46 Update statement.......................................................................47 Delete statement........................................................................47
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ABAP BASICS
Some Facts about SAP After the Internet, SAP R/3 is one of the hottest topics in the computer industry and the company that developed it. It is targeted to most industries, manufacturing, retail, oil & gas, pharmaceutical, banking, insurance, telecommunication, Transport, chemical and so on. All major hardware Vendors were fully engaged to partner with SAP: AT&T, BULL, Compaq, IBM, Sun have supported and certified R/3 platform. SAP has list of major consultants all over the world like Anderson Consulting, Price Waterhouse – Cooper & Lybrand, Ernst & Young, KPMG and many more. The company behind R/3 is SAP AG, founded by four former IBM employees in 1972. The company’s headquarters are in Walldorf, a small German town. The company name, SAP stands for SYSTEMS, APPLICATIONS and PRODUCTS in data processing. In 1992 R/3 was introduced and in 1995 SAP AG was ranked fifth among independent software vendors. One of the reasons for SAP’s success is that since it is a standard package, it can be configured in multiple areas and adapted to specific need of a company. Today, more than 21,600 customers in over 120 countries run more than 69,700 installations of SAP® software. With subsidiaries in more than 50 countries, the company is listed on several exchanges, including the Frankfurt stock exchange and NYSE under the symbol “SAP”. SAP has two main products in the business software market, Mainframe system R/2 and Clientserver R/3. Both are targeted to business application solutions. Here R indicates REAL TIME. R/2 is SAP AG mainframe software that runs on IBM, Siemens and other compatible equipment. This type of solution cannot be open, but with ALE technology, R/2 can be linked with R/3 system and share data. This system is mainly targeted at enterprises with data-intensive and centralized industries. R/3 is the product that has really placed SAP AG as the leader in the country. This complex Client/server system is core of our course. The global acceptance of R/3 is not only because it caters all complex needs of business but also this international acceptance is because of R/3’s international applicability. For SAP this does not mean having software available in different languages, but also covering currency, taxes, Legal practice concerning HR, Import/export regulations. SAP also values its customers and it is shown by the comprehensive set of quality services put by SAP to help customers during the process of implementing and supporting the R/3 systems. These services include product information; training, installation and upgrade service like:
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ABAP BASICS OSS: Online Service System is one of the primary sources of service and support provided by SAP. With OSS, customers can search the SAP information database and find solutions for errors and problems with R/3 systems. You can also submit your problems to SAP. Consulting Service: with remote consulting service customer receives immediate and updated technical support and answers to their questions. Maintenance service: This is the basic and most common type of support for customers in technical support and answers to their questions. Information Service: These are the various information sources for receiving detailed information about the R/3 system, marketing brochures, system documentation, training information and many more things. Preventive services: The primary one is the Early Watch Service, which ensures successful and efficient installation of the R/3 system in all phases. This service makes regular/performance checks and analyzes the system to identify potential problems, help system managers and SAP administrators to tune the system. Soon after the Early Watch session, SAP sends the customer a report with the result of the analysis and recommendations for avoiding potential problems such as database becoming full. So overall SAP R/3 is an open client/server software system, designed to manage business information needs of an entire enterprise. The whole dataflow of SAP R/3 works in an integrated way, which means the data needs to be entered just once and the system automatically updates other logically related data.
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ABAP BASICS WORKING WITH R/3 system The SAP R/3 presentation interface behaves very similarly to any other typical window application and is also known as SAPGUI. The first screen that you come across in R/3 system is SAP logon screen.
SAP R/3 logon Screen This is the first screen that appears when you use SAP logon utility. It has four fields: the client, the user, the password and the language.
Client: Here you enter the client number. The client is group of users who has similar rights. It can be group of users in a business entity or a whole business entity or a whole company. ♦ User: The name of the SAP user identification. Users of the SAP system are client-specific, which means that user belonging to one client is valid to only the particular client. ♦ Password: It is the password that has been assigned by the system administrator. ♦ Language: SAP R/3 system supports multinational language on the same system at the same time, which is very useful for multinational companies with different branches in several countries and possibly using different languages. After entering all the fields press ENTER key and system will take you to MAIN MENU screen.
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ABAP BASICS User might get different screens when he logs on, depending upon default settings of the user master record i.e., if user is DEVELOPER then the screen which he often works on is editor screen and he can go directly to this screen, if system administrator sets this screen for the user. Main features of any R/3 window are as follows: ♦ R/3 standard window elements behave exactly the same, as any other standard window application would, like minimizing a screen, setting the active window etc. ♦ From TOP to BOTTOM, R/3 window can contain typical elements such as check boxes, push buttons, input fields and following elements: ♦ Menu bar is the first element of the every R/3 window. It contains the menu item corresponding to the particular R/3 application. The two menu options SYSTEM and HELP are always present in every R/3 window. SYSTEM menu option contains all utilities and functions, and is available to user at all the times. The HELP menu contains all the available options for the different types and methods of obtaining online help in the system. ♦ Standard tool bar. The second R/3 window element is present in every R/3 window. It is nothing but a collection of icons, which perform common functions like saving the object, exit etc. The various icons on std. Tool bar are as follows (from left to right): Enter Command Field Save Back Exit Cancel Print Find Find Next First Page Previous Page Next Page Last Page Help All icons in R/3 window application support FOCUS property. It means, if you place cursor over an icon, the system will show the function of the icon. ♦ Application tool bar: The next part of the screen contains icons most commonly used in that particular task or transaction. ♦ Status bar is the bottom line of the screen and usually shows errors or information messages to the user. It also includes other information such as system id, session number, client, server name and the response time. In between application tool bar and status bar you have working area, which is different for different screens.
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ABAP BASICS
Logging Off User can log off the R/3 system from any screen. There are three ways of logging off the R/3 system, which are as follows:
♦ From the Menu bar choose SYSTEM → LOG OFF. In this case, you get the log off dialog box, which informs the user that any data not saved will be lost if continuing with the log off procedure. ♦ Use/NEX transaction code in the command field. This is dangerous, since it does not ask if you want to save the data. ♦ Clicking on the EXIT button on the R/3 initial screen.
Using Transaction Code The R/3 system provides an alternative and efficient way of selecting menu options for moving around the tasks and functions of the SAP system by using transaction code directly in the command field. When moving with transaction, you can go to any part of the system by merely typing a transaction code in the command field, provided you have authorization for that. That transaction code is the four-character code associated with any task. By typing the transaction code and pressing ENTER key, the system takes you directly to the initial screen for transaction. Whenever any transaction code is entered in the command field, it gets stored in the buffer memory. If you click on drop down arrow, system displays list of transaction code already entered and you can select from this list or enter new one. There are almost (12094) twelve thousand and ninety four transactions in SAP. For every task, transaction code is associated and it can be found by ♦ SYSTEM → STATUS Status window is popped up which contains the transaction code in the trans field. ♦ Through DYNAMIC MENU. It gives the list of tasks. If you click on the top line of the application areas and pressing the search and search next button will give you the transaction code. /N will take you to initial screen of R/3
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ABAP BASICS
Important transaction codes, which you will be using often, are: Editors • SE37 • SE38 • SE41 • SE51 • SE71
Function Builder ABAP/4 Editor Menu Painter Screen Painter Form Painter
Getting help in the R/3 system R/3 includes many possibilities to get online help for almost every element of the system, users can get help for entire application, for specific function, for definitions of various terms used in SAP, i.e., Glossary, messages, screens, fields etc. You obtain HELP by using any of the following options: ♦ Help function from the R/3 window, which is compulsory menu item of every R/3 window. ♦ ? Icon of standard tool bar. ♦ F1 function key. The SAP system provides help on most fields that appear on the R/3 system. To get help on particular field, position the cursor over it and press help button or F1 function key. Another way in which R/3 system provides help is when system displays error messages in the status bar. Double clicking on the status bar shows additional information about the message.
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ABAP BASICS
Working with R/3 user sessions A very important feature provided by SAP. In R/3 system you can work with more than one task at any given point of time, by means of opening sessions. You can call sessions as independent R/3 window where you can perform other tasks. By default, a user can open SIX sessions simultaneously and can work or move around with all sessions at the same time. Sessions can be closed at any time, without having to log off the system. User can create new sessions from anywhere as CREATE SESSION comes under SYSTEM menu which is available in every R/3 window. SYSTEM → CREATE SESSION Or /O in command field This will open a new session or window and will place it in front of all other windows.
To move among sessions ♦ Just mouse click on any part of the R/3 window to make that session active. ♦ Combination of ALT + TAB key.
R/3 Architecture The overall R/3 system includes the following components: Business Applications
Basis System Or Middle Layer
Operating System
Data Base
Network
The UPPER layer, the functional layer contains the different business application. The integration of all application depends upon basis system. Applications are developed in ABAP/4 Lang. (Advanced Business Application – the 4th generation language) The R/3 basis software is the set of programs and tools, which interfaces with the operating, system, the underlying database, protocols and the presentation interface. This layer enables all 11
ABAP BASICS the application to work exactly the same way no matter what operating system or database, the system is installed on. It is an independent layer and ensures the integration of all modules. Besides all these specific jobs, BASIS system also contains following components and thus provides more additional features. ♦ ABAP/4 development workbench, which in turn includes many features like repository, data dictionary, workbench organizer, which will be discussed in later part of the topics. ♦ ABAP/4 language, system administrative tools, all these components are used to control, tune the R/3 system. ♦ Spool system manages the formatting of data for printing and passing it to the host spool system. ♦ For background execution. Mail system you can send and receive mail from the outside world (Internet). ♦ Communication interface to external system from R/3 system: Manages communication at the OS level (TCP/IP), at the database level & between applications too. (RFC, EDI, and ALE) ♦ Database interface – This component supports different Relational databases from different vendors. The main task of database interface is to convert the SQL request from the SAP development environment to the database’s own SQL environment. ♦ Background processing with this facility you can submit your program BASIS system contains the layered components that facilitate the development of client/server architecture.
Client / Server architecture Client/Server architecture is mainly a software concept that includes a set of service providers and service requesters. The set of computers acts as service providers and is called as server. The sets of software component, which act as service requester, are called as client. In the client/server architecture, the database acts like a library clerk retrieving books from the shelf. The user programs have to request database for the data instead of searching for the data themselves. This way there is no risk of the users putting the data out of order. If the desired data is in use, the database makes the user wait until it is free. The major advantage of the client/server architecture is that the server is available for a number of clients and there is distribution of work between the clients and the server. The user directs the request to the client; the client in turn understands the user’s request and redirects the request to the server. The server retrieves the data, gives it to client. You can have client and server on the same machine or on different machines. Each client has a corresponding process inside the server. 12
ABAP BASICS
One of the most used client/server configurations with the R/3 system is the 3 tiered architecture, which separates a system’s computer into 3 functional groups:
Three tier architecture of R/3 Database Server Application Server Presentation Server (Unlike normal Client/server architecture where you have only two layers i.e., client and server.) Communication among the 3 tiers is accomplished by standard protocol services like TCP/IP or CPIC (Common Programming Interface Communication). Database Server
Application Server
Application Server
Application Server
Presentation Presentation Presentation Presentation Presentation Presentation Server Server Server Server Server Server In above case database server stores the data centrally. Basically contains database engine and associated processes. The database layers contain the database system used by all servers. Application server contains software components to run the program. It contains a SAP kernel, which can run ABAP/4 program. The presentation server is your client through which you send your request to application server. It is also called as SAP graphical user interfaces known as SAPGUI and is available in windows 3.1, Windows NT, Windows 95, and Macintosh. They all look similar whatever underlying system they are running on. The SAPGUI includes all graphical capabilities of window interface with menu bars, tool bars, focus property, and the entire mouse clicking operations.
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ABAP BASICS The R/3 system is open system in the sense that it can run on any operating system or any database and any communication technology. It means that: ♦ R/3 system can run on any operating system platform such as UNIX, NT, 95, AS/400. ♦ It supports various RDBMS such as SQL server, Oracle, Informix, DB2. ♦ Standard GUIs supported by R/3 are Windows 95, NT, Windows 3.1, and Macintosh. ♦ SAP can use standard communication protocols TCP/IP, CPIC, OSF/DCE/DME for network.
ABAP/4 Development Workbench The development environment of SAP R/3 system is fully integrated set of various development tools, data dictionary, and programming language. Full integration of all components means that changes in any part have a direct and immediate effect on all application using those components. The screen of ABAP/4 development workbench looks like
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ABAP BASICS Tools of ABAP/4 workbench For programming: ♦ ABAP/4 dictionary Defining, maintaining and storing the data dictionary of the SAP R/3 system stores all the dictionary objects including tables relationship and Help information. Transaction code for this is SE11. ♦ ABAP/4 editor Creating and maintaining the ABAP/4 program, editing function modules, logical database, and screens. Transaction code is SE38. ♦ Function library Defining and maintaining the ABAP/4 function modules. Transaction code is SE37. ♦ Screen painter Designing and maintaining the screens in transaction. Transaction Code is SE51. ♦ Menu painter Designing and maintaining the means for graphical user interface. Transaction code SE41. For Navigating: ♦ Object browser Managing and organizing the development object in a hierarchical form. Transaction code is SE80. ♦ ABAP/4 repository information Navigating and searching for the dictionary Objects, development objects and relationship objects. Transaction code SE84. ♦ Data browser Navigating in the data tables of the database. Transaction code is SE 16. For Debugging: ♦ SQL trace tracking the database calls from the system transaction and programs. Transaction code is ST05. ♦ Debugger Stopping the program and analyzing the results of the execution of every program statement. ♦ Runtime Analysis Analyzing the performance the system calls Transaction code is SE30 For Organizing: ♦ Workbench organizer controlling and keeping track of development work and team related development projects and managing versions of development objects. Transaction code is SE09. ♦ Transport system performing and managing the transport of development object across different system. Transaction code is SE01
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ABAP BASICS Data Dictionary The ABAP/4 dictionary is central workbench repository utility providing the data definition and the information relationship that are later used in all the business application within R/3 The ABAP/4 dictionary can be seen as a logical representation or a superior layer over the physical underlying database. This database must support the relational data model. This model is strictly followed by data dictionary.
About Data Dictionary A Data dictionary in computing terms is the source of information in which system data is defined. The data dictionary is the centralized and structured source of information for business applications. You can say that it is core of a well-structured development environment. The elements that make up a dictionary are known as metadata. Metadata is the term for the data whose function is to describe other data. Data in dictionary is not the actual data like emp. name or emp. address but rather a type of data whose function is to define the properties of the data such as type, length, and relationship.
Advantages Advantage of using data dictionary is avoiding inconsistencies when defining data type that will later be used in different applications. This avoids redundancies. When a type is defined in the dictionary, it is available to any program in the application. A change in the definition of a type of data in the dictionary automatically affects any other data or program, which has this data. Again, data dictionary is a fast and efficient way to answer questions such as which entries exist in a table of the database, what the structure of table is.
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ABAP BASICS Activation of dictionary objects For a dictionary object to be effective at runtime, that is, for a dictionary object to be available for use within a program, transaction, and so on, it must be in active status. For objects to become active, R/3 includes the ACTIVATION function. When a table or aggregated object is activated, it is placed at the disposal of the system as a runtime object in a way that makes it available quickly for the application program to access relevant information of new activated objects. When a dictionary object is modified, that means that the object previously existed and activated. You need to reactivate the object after modification. When mass activation is performed massively, it might take a quite a long time. Then it should be in the background system. This type of activation is known as background activation. The ABAP/4 Data dictionary is the central component of ABAP/4 repository. A Data dictionary is centralized and structured source of information for business application. The ABAP/4 dictionary is the core of the R/3 development system. It is the source of every definition, within R/3, from the very basic domain to the company data model. It is totally integrated with other tools of the development environment like screen painter, menu painter, and editor. Some of the main available functions in the ABAP/4 dictionary are as follows: ♦ Add, delete, modify, and manage the definition of the dictionary data. ♦ Preserve the data integrity. ♦ Be the central source of information e.g. from the dictionary you get the information about the defined relationship between two tables or even the directory tells whether table is active or empty. ♦ It also permits documentation of system data. In the R/3 system instead of working with original objects, you work with internal representation of objects. With this type of operation the system performance is enhanced and has the advantage that the development tools, screen interpreters always access current data. When any of the data dictionary objects are used in other parts of the development workbench for example, in program, programmer only has to enter a table name or field name. The system automatically knows all the properties and information of the field.
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ABAP BASICS
To call ABAP/4 dictionary, from the main menu, Tools → ABAP/4 workbench → data dictionary or enter transaction SE11.
Data dictionary objects: ♦ Table: is a 2D data matrix containing rows and columns. Rows contain data while column indicates fields. Table can contain 0 or multiple rows. ♦ Structure: is a skeletal view of a table. It contains the definition of columns and don’t have any contents. Structure is generally a template based on which a table is created. The basic difference between structure and table is that the structure does not exist at the underlying database system level. Structure exists as definition in the dictionary. ♦ Views: A view is an imaginary table. It contains data, which is really stored in other tables. The contents for the view are dynamically generated when called from program. ♦ Data element: is definition of the properties and type for a table field. It is an intermediate object between the object type domain and the table field. A field in R/3 system is always associated with a data element, which at the same time is related to domain.
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ABAP BASICS ♦ Domain: is formal definition of the data type from a technical point of view. It sets the attributes such as data type, length, possible value range and so on. ♦ Lock objects: These types of objects are used for locking the access to database records in table. This mechanism is used to enforce data integrity that is two users cannot update the same data at the same time. With lock objects you can lock table-field or whole table. ♦ Search Help Objects: , which gives list of possible values for either primary keys or nonprimary keys.
Tables in ABAP/4 dictionary Tables are the basic objects in R/3 application. There are almost 8000 tables in R/3 system. Following types of tables are available • • •
Transparent tables Pool tables Cluster tables
From user point of view, all tables are used to store data whatever be the type of table. There is no difference in the behavior or operation of these tables. All of them can be managed by using standard OPEN SQL. However from an administrator point of view transparent table do exists with the same structure both in the dictionary as well as in the database, exactly with the same data and fields. While other two are not transparent in the sense that they are not manageable directly using database system tools. You can access these tables in R/3 environment from the ABAP/4 dictionary. You cannot use native SQL on these tables. Pool or cluster tables are logical tables, which are arranged as records of transparent table. A table is made up of rows and columns. When the table is created, its columns are named; data type is supplied for each column. There can be only one data value in each column of each row in a table. Record or as it is called in different RDBMS is nothing but group of fields. While a column is a field of a table, a table is an indexed file. The main index is called as primary key, which can be a single field or combination of keys or fields. A primary key can be defined as a field, which indefinites a single unique record of the table. A table cannot have record with duplicate primary key. In any RDBMS, tables are related to each other. But to relate table to each other it is necessary that one of the tables contain some information of other table. Mostly tables are related to each other through primary keys. The primary key of one table, if it exists in other table then it is called foreign key. This type of database management system means that there is some redundancy of data. But using normalization procedures available can minimize it. One of the most important functions of foreign key is to ensure data integrity. For example say you have 19
ABAP BASICS EMP table, which has fields: emp. no., emp. name, dept. code, salary and you have DEPT tables, which has dept. code and dept. desc. Then in DEPT table dept. is primary key while dept. code in EMP table is foreign key. If you enter dept.code for particular employee in EMP table the dept.code should exist in DEPT table. System will check the value for dept.code in DEPT table, and if does not exist then will flash error. In this case DEPT is called check table while EMP is foreign key table.
Creation of table Steps to create a table ♦ Create domain ♦ Create data element ♦ Create actual table
Creating Domain Domain as already explained defines the technical properties of a field such as type and value range. A domain can be created from initial screen of data dictionary by clicking on create and clicking domain Radiobutton. Parameters to be passed are: Data type: Where you need to enter the data type available in SAP. Field length: Field length is the number of valid position. Value table: Name of a table to be entered. The fields referring to this domain may only assume values contained in the value table. Once the domain is created, save and activate it, so that it can be used for further objects (basic rule of dictionary).
Creating Data Element The second step of table creation is to create data element. It assigns a certain meaning to the table field, which are defined using that data element. A Data element always needs to be defined over a domain and field is always defined over a data element. This allows all fields with same technical properties to use the same data element. Parameters to be passed when creating a data element: Short text: Mandatory field. Domain: A mandatory field. If the domain does not exist, SAP can take you directly to domain definition screen. 20
ABAP BASICS Text element: You can enter description is short or long text for the field. This text is used when entering data for these fields. Save and activate. Creation of actual table Parameters to be passed for creation of table: Short description: Delivery class: Table fields: element. Data class: Size category:
Mandatory field. As per User Requirement Specify whether primary key. In this case it is mandatory to enter data Establishes the physical area of the database. Allows you to specify estimated space requirement for the table.
Further down under buffering square box, the system allows specifying whether table is going to be buffered. When a table is buffered, it is loaded into the table buffer from the application server memory and it will remain there until you switch off or reboot system. If the table is to be buffered, you need to specify the type of buffering. Full is for entire table while partial is for only those records which are being accessed. Once the table is created, it has to be generated or activated to be able to access by other objects like programs. General Introduction to ABAP/4 SAP originally developed the programming language ABAP/4 (Advanced Business Application Programming) for internal use to provide best working conditions for developers. SAP constantly improves the language to adapt to the increasing requirements of the business applications. At present, ABAP/4 is the only tool for developing applications at SAP. SAP customers use ABAP/4 for their own developments. The ABAP/4 Development Workbench contains all tools you need to create and maintain ABAP/4 programs. ABAP/4 programs are not complied but generated. During generation, the system creates a so-called runtime object from the source code and the program attributes. When you start the program, the system executes the runtime object. ABAP/4, a fourth generation language, contains all usual control structures and modularizing concepts for structured programming. The three parts of the ABAP/4 language are:
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ABAP BASICS Structure and execution of ABAP/4 programs Basic language elements Programming reports Programming dialogs Structure and execution of ABAP/4 programs are essentially different from entirely sequential programming languages such as FORTRAN, PASCAL, or C. ABAP/4 instead shares certain similarities with modular, event-orient programming languages such as Visual Basic or JAVA. The two most important statements concerning structure and execution are: An ABAP/4 program has a modular structure. For execution, you need a special runtime environment. This means, that ABAP/4 source texts always consist of a collection of program modules (one single module in the easiest case) or the sequential set of statements. The individual program modules consist of sequential elements. The set of statements of a program module is also called processing block. The runtime environment is responsible for calling the individual program modules one after the other. The runtime environment is the ABAP/4 processor, which can communicate with the list processor or the dialog processor, depending on the program type. Program flow within the individual processing blocks is sequential, as you know it from other sequential programming languages (for example, FORTRAN, PASCAL and C). Within the processing blocks, you can use the general control statements for the program flow, such as IF, DOES, WHILE, ABAP/4 does not contain GOTO elements. We mainly use programs that consist of a single processing block only and, therefore, behave most likely like programs of other sequential programming languages. For programming applications, the entirely sequential concept is not sufficient. SAP distinguishes between two general types of application programs: Reports: You use reports to read databases and represent the results in lists. Reports are collections of processing blocks that the system calls depending on events. Dialog programs: You can dialog programs to execute transactions, which usually read and change databases. Dialog programs are collections of processing blocks (so-called module pools) that are called by a screen flow logic. The third part of the User’s Guide describes dialog programming in detail. Reports can call dialog programs and vice versa.
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ABAP BASICS In its easiest version, an ABAP/4 program contains one single sequential piece of coding and, thus, one single processing block. Characteristics of the ABAP/4 programming languages ♦ Declarative elements for declaring data of different type and structures. ♦ Operational elements for manipulating data. ♦ Control elements to control processing flow. ♦ ABAP/4 is multi-lingual. Text elements such as titles, headings, and text body are stored separately, independent of the program codes. Thus, you can change, translate, and maintain text elements without having no adapt the coding. ♦ ABAP/4 supports business-related data types and operations. You can execute calculations using special data and time fields. The system automatically executes all necessary type conversions. ♦ ABAP/4 provides a number of functions for processing character strings. ♦ ABAP/4 allows you to define and call subroutines. You can even call subroutines of other programs. There are different ways of how to pass parameters to and from the Subroutines. ♦ ABAP/4 contains a special type of subroutine, called function module. Function modules are stored and maintained in a central library. They have clearly defined data interfaces to the calling program. You can test function modules in a stand-alone mode independent of the calling program. ♦ ABAP/4 contains an SQL subset called OPEN SQL. OPEN SQL allows you to read and change database tables independent of the underlying database system. ♦ ABAP/4 allows you to define and process internal tables that exist only for the execution period of the program. Internal tables efficiently support the usage of database tables and allow you to implement complex data structures in a program. ♦ ABAP/4 allows you to store data not only in databases but also as sequential files on application and presentation servers.
REPORTS ♦ Reports are ABAP/4 programs. ♦ You use reports to evaluation data from database tables. The results of such an evaluation can be displayed on the screen or printed form. ♦ Reports are stand-alone programs. ♦ The user can execute reports directly via the program name, for example, by choosing System ® Utilities ® Reporting. ♦ A report program contains a collection of processing blocks for different events that are always triggered externally. In a report, you can react on events by programming the corresponding processing blocks or ignore the events by not writing the corresponding processing blocks. A report itself never creates events. 23
ABAP BASICS ♦ Reports can use logical databases or select statements defined by developer. ♦ For each application, SAP supplies logical databases. Or you can easily create logical database yourself. ♦ Event control of a report corresponds to a certain scheme: When a report is executed, the ABAP/4 processor creates together with the logical database used (if any) a sequence of certain events for which you can program processing blocks. The chronology of the events is (more or less) Steps involved in creating a Report: 1. Processing the selection screen After starting a report, the selection screen allows the user to enter limits or control values for further report processing. The report can contain several processing blocks for events during selection screen processing, for example, for checking the input values. 2. Reading the database After selection screen processing come the events for reading the database. Either the report reads data from relational databases it using the corresponding ABAP/4 statements (open SQL) or leaves this task to a logical database. In the latter case, the logical database creates a sequence of events to allow the report to copy the data. 3. Evaluating data and creating lists During or after reading the database the report creates the output list. During list creation, several events allow you to layout the output list (for example, layout the page header). 4. Outputting a list The last part of the processing sequence controlled by the ABAP/4 processor is the list output on the screen or printer. When displaying the list on the screen, user can trigger other reports, that are interactive and are event driven. For example, by clicking the mouse. By programming processing blocks for these events, you change a normal report to a so-called Interactive report. If a report does not contain event keywords, the entire coding of the report belongs to a single processing block, which is called by a standard event. This standard event is triggered directly after processing the selection screen.
DIALOG PROGRAMS ♦ You use dialog programs to execute transactions. The users of dialog programs in dialog sessions read and change database tables. Apart from the actual data processing (Open SQL), update and enqueue concepts are of great importance when programming dialogs. ♦ Dialog programs are not stand- alone
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ABAP BASICS ♦ To execute dialog programs, they must be linked to at least one screen that itself is linked to a transaction code. The transaction code determines the initial screen with which the dialog session starts. ♦ Dialog programs are controlled by screen flow logic ♦ The actual ABAP/4 dialog program is a so-called module pool. A module pool contains a collection of dialog modules that are called by the screen flow logic. ♦ To each module pool, at least one, but usually several screens are allocated. Each screen has flow logic. The flow logic consists of PBO (process Before output) and PAI (process After Input) blocks. This flow logic does not use the ABAP/4 programming language and the ABAP/4 Editor tool, but a special statement set and the Screen Painter tool, which you also use to layout screens. The flow logic mainly contains the chronologically ordered calls of the modules in the corresponding module pool. ♦ The collection of PBO flow logic, screen, and PAI flow logic is called Dynamic program (Dynpro). A module pool must have at least one dynpro. Each screen of a dialog session thus is the visible part of a dynpro, to which also the flow logic belongs. The processing logic of a dialog session is stored in the corresponding module pool in the form of ABAP/4 modules. ♦ The ABAP/4 modules in the module pool are separated into PBO and PAI modules. The PBO or PAI blocks of the flow logic of each dynpro of a module pool can call each PBO or PAI module of this module pool. ♦ You can use ABAP/4 statements in the processing logic of the module pool to control the chronology of the different dynpros. After starting a dialog session via the transaction code, which is firmly connected to a dynpro of the module pool, the screen flow logic passes user entries to the processing logic in the ABAP/4 module pool. The processing logic processes the user entries (database accesses) and, if required, defines the appropriate subsequent screens.
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ABAP BASICS Data Types and Data Objects Data types and data objects are essential components of the ABAP/4 type concepts. Both can be declared and maintained by user. Unlike other programming languages in ABAP/4 you can create DATA TYPES independently. Data Types ♦ Are pure descriptions ♦ No memory is associated with data types. ♦ Describes the technical properties of data objects. Structure and definition classify data types. Can be of: 1. Elementary or structured 2. Predefined or user defined
ELEMENTARY
STRUCTURED
Predefined
User-defined
C, D, F, I, N, P, T, X
Based upon elementary Data types.
You can use directly
E.g., TYPES: number types I. Can’t allocate memory to types.
Predefined types are TABLES
User defined structured types are Field String and internal tables.
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ABAP BASICS Data Objects ♦ Data objects are units created during runtime. ♦ Data object cannot exist without data type. ♦ Occupies memory space. Kinds of Data Objects 1.
INTERNAL DATA OBJECTS
♦ Literal A literal has a fixed value. Ex WRITE: “WORK HARD” ♦ Variables DATA statement is used to create variables Ex DATA: NUM TYPE I NUM is a variable declared by DATA statement. Any variable, which you use in program, need to be declared before you use it and can be done by DATA statement. Here variable is declared by referring to existing data type. Variable can also be declared by referring existing data object. Ex. We have already declared NUM by DATA statement. DATA: PRICE LIKE NUM. Here variable is declared by using LIKE parameter, which tells system that price has all the attributes of data object NUM i.e., PRICE is also of type I. The main difference between TYPE and LIKE parameter when defining or declaring the object is that TYPE is used to refer existing DATA TYPE (elementary or structured or user defined) while LIKE is used to declare data objects with reference to existing DATA OBJECTS. ♦ Constant Constant is a data object, which contains fixed value through out the program. Constant can be declared in program by using CONSTANT statement. Ex. CONSTANT: INT TYPE I VALUE 15. 27
ABAP BASICS
In program value of INT cannot be changed. If you give a statement like INT = 20. In this case system will give error. 2.
EXTERNAL DATA OBJECTS Are defined in tables i.e., in ABAP/4 dictionary. You can access this data from table. TABLES: SFLIGHT DATA: SEATS LIKE SFLIGHT-SEATSMAX.
3.
SYSTEM-DEFINED DATA OBJECTS SPACE & SYSTEM VARIABLES like sy-uname, sy-datum, & sy-repid.
4.
SPECIAL DATA OBJECTS PARAMETERS: are variable, which can accept value from user. SELECTIONS CRITERIA: are special internal tables to accept value range from user.
Need for Data types: Consider the following example. DATA: fname(20), mname(20), lname(20), add1(20), add2(20), add3(20). If you have DATA statement like above, and if you need to change the length of all the fields say from 20 to 25, then you need to change all the fields i.e., going through each and every statement. But consider the following case where TYPES has been used. TYPES:str(20) DATA:fname type str, 28
ABAP BASICS Mname type str, Lname type str, Add1 type str, Add2 type str, Add3 type str. In this case if you need to change the length of all fields from 20 to 25. Then just change the length of STR and change will be reflected for all the fields. If you define all the types in TYPE-POOL i.e., global definition of all the types, you can use these types anywhere and in any program.
Parameters Parameter statement is used to accept input from user. PARAMETER statement is used when you want user to enter data and depending upon what he enters you need to take action. The parameter statement declares the variable and also allows system to accept data into that variable. Syntax. Parameters: num type I. Here parameter statement declares the variable and creates the selection screen on which user enters the data i.e., in this case num is declared of type I and user can enter any number. Entered value is stored in the same variable and can be used in program. Data: m type I Parameters: num type I M = num – 5 Write: / ‘The number is’, m. You can define default values with parameter statement for example Parameter: num type I default 12. In this case when selection screen is displayed the default value is displayed. User can either use same value or overwrite the value. Parameter of type character and length = 1, can be displayed as Checkbox and Radiobutton. Parameter: C1 as Checkbox, C2 as Checkbox. Parameter: R1 Radiobutton group g1, R2 Radiobutton group g1. When parameter is defined as Radiobutton, it needs to be attached to one group. Only one Radiobutton of one group can be clicked.
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ABAP BASICS Every parameter can be associated with language dependent text that is displayed on the selection screen. This can be done with the help of text elements.
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ABAP BASICS WRITE Statement The basic APAB/4 statement for outputting data on the screen is WRITE. Syntax: WRITE