Difference between fixed focus and auto focus?

what is difference between fixed focus and auto focus and which is better?

Thanks for the advice Phonehacker, this Forum is so helpful on a variety of subjects, and the users are so patient, that's why I enjoy it so much   My diet is now perfectly organised and my larder is full of Brown Bread and Red Wine 
If I have helped at all, a click on the White Star is always appreciated :
you can also help others by marking 'accept as solution' 

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  • Difference between reversing journal and Auto reversal journal in HFM

    What is the difference between Auto reversing journal and Auto reversal journal in HFM?

    Hi Dev,
    The below link might be helpful:
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    Refer to page 173
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    Charles Babu J

  • Should I spend the $280.00 to have Canon fix my 70D auto-focusing issue?

    Should I spend the $280.00 to have Canon fix my 70D auto-focusing issue? Or just return back to my very much trusted Rebels?
    Solved!
    Go to Solution.

    MelekalsCanon wrote:
    Very much appreciate your taking time to send a response. As a new user I wasn't sure if anyone would bother. Allow me to add a little more to my first post. I fit in that niche between amateur and a person with clients. For over 10 years I have covered events for a non-profit agency capturing the look and feel of 20+ events per year and was given permission to purchase a few cameras over the year. My decision from the beginning was to use the Canon Rebel. Images were spot on and only once did I have an issue with one of them (after shooting outside events in 105 degree temps for 3 days).
    So, when I retired a year ago it was for me a pretty simple choice to get a Canon for myself - especially since at that time the 70D was on the cover of magazines and was very highly touted. I also did a lot of desktop publishing and photo editing which helped me realize I wanted the best sensor, sharpness, resolution and lens I could afford - the 70D. My post was actually a result of reading many online responses including your very informative replies about the 70D focusing issues. My biggest concern is that I will spend several hundred dollars and maybe, just maybe get back a camera which captures better focused images, but still not as sharp as the lower end Rebels I was using. I had hoped to purchase my first "L" lens and really get excited - not repair the most expensive camera I've bought to date.
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    Let me clarify that I don't own a 70D, so anything I say about it is from watching what others have said, mainly in this forum. But it is disconcerting to see so much complaint about a camera that's supposed to have an innovative focusing system. One is strongly tempted to suspect that they went overboard in trying to make the camera serve both still  photographers and videographers.
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    As far as spending the $280 for the repair, I understand why it's a hard call. If I were in your shoes and were convinced that Canon understands the issue and would fix it correctly and permanently, I guess I'd go for it. If you don't think they do, but fell that you need something a cut above the Rebels, this may be a good time to buy a leftover or refurbished 7D. Even though I now have a 5D3, I still use my 7D's a fair amount and have been very happy with them. And the 7D2 has gotten such a favorable reception that's it's almost bound to make more 7D's available at a decent price.
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  • Difference between Preffered Vendor and Normal/Fixed Vendor

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  • What is the difference between Fixed Costed, Costed and Distributed?

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    Check under heading 'Costing' on HRMS guide, link is here
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  • Difference between Fixed order qty and Fixed Lot multiplier

    Hi All,
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    Hi,
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  • What is the difference between jsp :include and server side include

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  • Difference between a Search and a Retrieve web service?

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  • Difference between Smart Forms and Adobe Form

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    Best Regards
    Srikanth

    Hi,
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    Regards,
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  • Difference between EDN-DB and EDN-JMS implementation

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  • What's the Difference between Time Capsule and OS X Server?

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    Did i do something to cast your anger upon me o mighty Camelot, backed up bypterobyte?
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  • What is the difference between 'Shopping cart' and 'Team cart'

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  • Difference between Data-centric and Document-centric use

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    Message was edited by:
    Marco Gralike

  • Differences between Procedural ABAP and OOPs ABAP

    Hi Friends,
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    Thanks and Regards
    Vijaya

    Hi
    Core ABAP (procedural) works with Event driven, subroutine driven one
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    see the doc
    ABAP is one of many application-specific fourth-generation languages (4GLs) first developed in the 1980s. It was originally the report language for SAP R/2, a platform that enabled large corporations to build mainframe business applications for materials management and financial and management accounting. ABAP used to be an abbreviation of Allgemeiner Berichtsaufbereitungsprozessor, the German meaning of "generic report preparation processor", but was later renamed to Advanced Business Application Programming. ABAP was one of the first languages to include the concept of Logical Databases (LDBs), which provides a high level of abstraction from the basic database level.
    The ABAP programming language was originally used by SAP developers to develop the SAP R/3 platform. It was also intended to be used by SAP customers to enhance SAP applications – customers can develop custom reports and interfaces with ABAP programming. The language is fairly easy to learn for programmers but it is not a tool for direct use by non-programmers. Good programming skills, including knowledge of relational database design and preferably also of object-oriented concepts, are required to create ABAP programs.
    ABAP remains the language for creating programs for the client-server R/3 system, which SAP first released in 1992. As computer hardware evolved through the 1990s, more and more of SAP's applications and systems were written in ABAP. By 2001, all but the most basic functions were written in ABAP. In 1999, SAP released an object-oriented extension to ABAP called ABAP Objects, along with R/3 release 4.6.
    SAP's most recent development platform, NetWeaver, supports both ABAP and Java.
    Implementation
    Where does the ABAP Program Run?
    All ABAP programs reside inside the SAP database. They are not stored in separate external files like Java or C++ programs. In the database all ABAP code exists in two forms: source code, which can be viewed and edited with the ABAP workbench, and "compiled" code ("generated" code is the more correct technical term), which is loaded and interpreted by the ABAP runtime system. Code generation happens implicitly when a unit of ABAP code is first invoked. If the source code is changed later or if one of the data objects accessed by the program has changed (e.g. fields were added to a database table), then the code is automatically regenerated.
    ABAP programs run in the SAP application server, under control of the runtime system, which is part of the SAP kernel. The runtime system is responsible for processing ABAP statements, controlling the flow logic of screens and responding to events (such as a user clicking on a screen button). A key component of the ABAP runtime system is the Database Interface, which turns database-independent ABAP statements ("Open SQL") into statements understood by the underlying DBMS ("Native SQL"). The database interface handles all the communication with the relational database on behalf of ABAP programs; it also contains extra features such as buffering of frequently accessed data in the local memory of the application server.
    Basis
    Basis sits between ABAP/4 and Operating system.Basis is like an operating system for R/3. It sits between the ABAP/4 code and the computer's operating system. SAP likes to call it middleware because it sits in the middle, between ABAP/4 and the operating system. Basis sits between ABAP/4 and the operating system. ABAP/4 cannot run directly on an operating system. It requires a set of programs (collectively called Basis) to load, interpret, and buffer its input and output. Basis, in some respects, is like the Windows environment. Windows starts up, and while running it provides an environment in which Windows programs can run. Without Windows, programs written for the Windows environment cannot run. Basis is to ABAP/4 programs as Windows is to Windows programs. Basis provides the runtime environment for ABAP/4 programs. Without Basis, ABAP/4 programs cannot run. When the operator starts up R/3, you can think of him as starting up Basis. Basis is a collection of R/3 system programs that present you with an interface. Using this interface the user can start ABAP/4 programs. To install Basis, an installer runs the program r3inst at the command-prompt level of the operating system. Like most installs, this creates a directory structure and copies a set of executables into it. These executables taken together as a unit form Basis.
    To start up the R/3 system, the operator enters the startsap command. The Basis executables start up and stay running, accepting requests from the user to run ABAP/4 programs.
    ABAP/4 programs run within the protective Basis environment; they are not executables that run on the operating system. Instead, Basis reads ABAP/4 code and interprets it into operating system instructions. ABAP/4 programs do not access operating system functions directly. Instead, they use Basis functions to perform file I/O and display data in windows. This level of isolation from the operating system enables ABAP/4 programs to be ported without modification to any system that supports R/3. This buffering is built right into the ABAP/4 language itself and is actually totally transparent to the programmer.
    Basis makes ABAP/4 programs portable. The platforms that R/3 can run on are shown in Table. For example, if you write an ABAP/4 program on Digital UNIX with an Informix database and an OSF/Motif interface, that same program should run without modification on a Windows NT machine with an Oracle database and a Windows 95 interface. Or, it could run on an AS/400 with a DB2 database using OS/2 as the front-end.
    SAP also provides a suite of tools for administering the Basis system. These tools perform tasks such as system performance monitoring, configuration, and system maintenance. To access the Basis administration tools from the main menu, choose the path Tools->Administration.
    Platforms and Databases Supported by R/3
    Operating Systems Supported Hardware Supported Front-Ends Supported Databases
    AIX SINIX IBM SNI SUN Win 3.1/95/NT DB2 for AIX
    SOLARIS HP-UX Digital HP OSF/Motif Informix-Online
    Digital-UNIX Bull OS/2 Oracle 7.1
    Windows NT AT&T Compaq Win 3.1/95/NT Oracle 7.1
    Bull/Zenith OSF/Motif SQL Server 6.0
    HP (Intel) SNI OS/2 ADABAS D
    OS/400 AS/400 Win95 OS/2 DB2/400
    SAP Systems and Landscapes
    All SAP data exists and all SAP software runs in the context of an SAP system. A system consists of a central relational database and one or more application servers ("instances") accessing the data and programs in this database. A SAP system contains at least one instance but may contain more, mostly for reasons of sizing and performance. In a system with multiple instances, load balancing mechanisms ensure that the load is spread evenly over the available application servers.
    Installations of the Web Application Server (landscapes) typically consist of three systems: one for development, one for testing and quality assurance, and one for production. The landscape may contain more systems, e.g. separate systems for unit testing and pre-production testing, or it may contain fewer, e.g. only development and production, without separate QA; nevertheless three is the most common configuration. ABAP programs are created and undergo first testing in the development system. Afterwards they are distributed to the other systems in the landscape. These actions take place under control of the Change and Transport System (CTS), which is responsible for concurrency control (e.g. preventing two developers from changing the same code at the same time), version management and deployment of programs on the QA and production systems.
    The Web Application Server consists of three layers: the database layer, the application layer and the presentation layer. These layers may run on the same or on different physical machines. The database layer contains the relational database and the database software. The application layer contains the instance or instances of the system. All application processes, including the business transactions and the ABAP development, run on the application layer. The presentation layer handles the interaction with users of the system. Online access to ABAP application servers can go via a proprietary graphical interface, the SAPGUI, or via a Web browser.
    Transactions
    We call an execution of an ABAP program using a transaction code a transaction. There are dialog, report, parameter, variant, and as of release 6.10, OO transactions. A transaction is started by entering the transaction code in the input field on the standard toolbar, or by means of the ABAP statements CALL TRANSACTION or LEAVE TO TRANSACTION. Transaction codes can also be linked to screen elements or menu entries. Selecting such an element will start the transaction.
    A transaction code is simply a twenty-character name connected with a Dynpro, another transaction code, or, as of release 6.10, a method of an ABAP program. Transaction codes linked with Dynpros are possible for executable programs, module pools, and function groups. Parameter transactions and variant transactions are linked with other transaction codes. Transaction codes that are linked with methods are allowed for all program types that can contain methods. Transaction codes are maintained in transaction SE93.
    So, a transaction is nothing more than the SAP way of program execution—but why is it called “transaction”? ABAP is a language for business applications and the most important features of business applications were and still are are transactions. Since in the early days of SAP, the execution of a program often meant the same thing as carrying out a business transaction, the terms transaction and transaction code were chosen for program execution. But never mix up the technical meaning of a transaction with business transactions. For business transactions, it is the term LUW (Logical Unit of Work) that counts. And during one transaction (program execution), there can be many different LUW’s.
    Let’s have a look at the different kind of transactions:
    Dialog Transaction
    These are the most common kind of transactions. The transaction code of a dialog transaction is linked to a Dynpro of an ABAP program. When the transaction is called, the respective program is loaded and the Dynpro is called. Therefore, a dialog transaction calls a Dynpro sequence rather than a program. Only during the execution of the Dynpro flow logic are the dialog modules of the ABAP program itself are called. The program flow can differ from execution to execution. You can even assign different dialog transaction codes to one program.
    Parameter Transaction
    In the definition of a parameter transaction code, a dialog transaction is linked with parameters. When you call a parameter transaction, the input fields of the initial Dynpro screen of the dialog transaction are filled with parameters. The display of the initial screen can be inhibited by specifying all mandatory input fields as parameters of the transaction.
    Variant Transaction
    In the definition of a variant transaction code, a dialog transaction is linked with a transaction variant. When a variant transaction is accessed, the dialog transaction is called and executed with the transaction variant. In transaction variants, you can assign default values to the input fields on several Dynpro screens in a transaction, change the attributes of screen elements, and hide entire screens. Transaction variants are maintained in transaction SHD0.
    Report Transaction
    A report transaction is the transaction code wrapping for starting the reporting process. The transaction code of a report transaction must be linked with the selection screen of an executable program. When you execute a report transaction, the runtime environment internally executes the ABAP statement SUBMIT—more to come on that.
    OO Transaction
    A new kind of transaction as of release 6.10. The transaction code of an OO transaction is linked with a method of a local or global class. When the transaction is called, the corresponding program is loaded, for instance methods an object of the class is generated and the method is executed.
    Types of ABAP programs
    In ABAP, there are two different types of programs:
    Report programs(Executable pools)
    A Sample ReportReport programs AKA Executable pools follow a relatively simple programming model whereby a user optionally enters a set of parameters (e.g. a selection over a subset of data) and the program then uses the input parameters to produce a report in the form of an interactive list. The output from the report program is interactive because it is not a passive display; instead it enables the user, through ABAP language constructs, to obtain a more detailed view on specific data records via drill-down functions, or to invoke further processing through menu commands, for instance to sort the data in a different way or to filter the data according to selection criteria. This method of presenting reports has great advantages for users who must deal with large quantities of information and must also have the ability to examine this information in highly flexible ways, without being constrained by the rigid formatting or unmanageable size of "listing-like" reports. The ease with which such interactive reports can be developed is one of the most striking features of the ABAP language.
    The term "report" is somewhat misleading in the sense that it is also possible to create report programs that modify the data in the underlying database instead of simply reading it.
    A customized screen created using Screen Painter,which is one of the tool available in ABAP workbench(T-code = SE51).
    Online programs
    Online programs (also called module pools) do not produce lists. These programs define more complex patterns of user interaction using a collection of screens. The term “screen” refers to the actual, physical image that the users sees. Each screen also has a “flow logic”; this refers to the ABAP code invoked by the screens, i.e. the logic that initializes screens, responds to a user’s requests and controls the sequence between the screens of a module pool. Each screen has its own Flow Logic, which is divided into a "PBO" (Process Before Output) and "PAI" (Process After Input) section. In SAP documentation the term “dynpro” (dynamic program) refers to the combination of the screen and its Flow Logic.
    Online programs are not invoked directly by their name, but are associated with a transaction code. Users can then invoke them through customizable, role-dependent, transaction menus.
    Apart from reports and online programs, it is also possible to develop sharable code units such as class libraries, function libraries and subroutine pools.
    Subroutine Pools
    Subroutine pools, as the name implies, were created to contain selections of subroutines that can be called externally from other programs. Before release 6.10, this was the only way subroutine pools could be used. But besides subroutines, subroutine pools can also contain local classes and interfaces. As of release 6.10, you can connect transaction codes to methods. Therefore, you can now also call subroutine pools via transaction codes. This is the closest to a Java program you can get in ABAP: a subroutine pool with a class containing a method – say – main connected to a transaction code!
    Type Pools
    Type pools are the precursors to general type definitions in the ABAP Dictionary. Before release 4.0, only elementary data types and flat structures could be defined in the ABAP Dictionary. All other types that should’ve been generally available had to be defined with TYPES in type pools. As of release 4.0, type pools were only necessary for constants. As of release 6.40, constants can be declared in the public sections of global classes and type pools can be replaced by global classes.
    Class Pools
    Class pools serve as containers for exactly one global class. Besides the global class, they can contain global types and local classes/interfaces to be used in the global class. A class pool is loaded into memory by using one of its components. For example, a public method can be called from any ABAP program or via a transaction code connected to the method. You maintain class pools in the class builder.
    Interface Pools
    Interface pools serve as containers for exactly one global interface—nothing more and nothing less. You use an interface pool by implementing its interface in classes and by creating reference variables with the type of its interface. You maintain interface pools in the class builder.
    ABAP Workbench
    The ABAP Workbench contains different tools for editing Repository objects. These tools provide you with a wide range of assistance that covers the entire software development cycle. The most important tools for creating and editing Repository objects are:
    ABAP Editor for writing and editing program code
    ABAP Dictionary for processing database table definitions and retrieving global types
    Menu Painter for designing the user interface (menu bar, standard toolbar, application toolbar, function key assignment)
    Screen Painter for designing screens (dynamic programs) for user dialogs
    Function Builder for displaying and processing function modules (routines with defined interfaces that are available throughout the system)
    Class Builder for displaying and processing ABAP Objects classes
    The ABAP Dictionary
    Enforces data integrity
    Manages data definitions without redundancy
    Is tightly integrated with the rest of the ABAP/4 Development Workbench.
    Enforcing data integrity is the process of ensuring that data entered into the system is logical, complete, and consistent. When data integrity rules are defined in the ABAP/4 Dictionary, the system automatically prevents the entry of invalid data. Defining the data integrity rules at the dictionary level means they only have to be defined once, rather than in each program that accesses that data.
    The following are examples of data lacking integrity:
    A date field with a month value of 13
    An order assigned to a customer number that doesn’t exist
    An order not assigned to a customer
    Managing data definitions without redundancy is the process of linking similar information to the same data definition. For example, a customer database is likely to contain a customer’s ID number in several places. The ABAP Dictionary provides the capability of defining the characteristics of a customer ID number in only one place. That central definition then can be used for each instance of a customer ID number.
    The ABAP Dictionary’s integration with the rest of the development environment enables ABAP programs to automatically recognize the names and characteristics of dictionary objects.
    Additionally, the system provides easy navigation between development objects and dictionary definitions. For example, as a programmer, you can double-click on the name of a dictionary object in your program code, and the system will take you directly to the definition of that object in the ABAP/4 Dictionary.
    When a dictionary object is changed, a program that references the changed object will automatically reference the new version the next time the program runs. Because ABAP is interpreted, it is not necessary to recompile programs that reference changed dictionary objects.
    ABAP Syntax
    The syntax of the ABAP programming language consists of the following elements:
    Statements
    An ABAP program consists of individual ABAP statements. Each statement begins with a keyword and ends with a period.
    "Hello World" PROGRAM
    WRITE 'Hello World'.
    This example contains two statements, one on each line. The keywords are PROGRAM and WRITE. The program displays a list on the screen. In this case, the list consists of the line "My First Program".
    The keyword determines the category of the statement. For an overview of the different categories, refer to ABAP Statements.
    Formatting ABAP Statements
    ABAP has no format restrictions. You can enter statements in any format, so a statement can be indented, you can write several statements on one line, or spread a single statement over several lines.
    You must separate words within a statement with at least one space. The system also interprets the end of line marker as a space.
    The program fragment
    PROGRAM TEST.
    WRITE 'This is a statement'.
    could also be written as follows:
    PROGRAM TEST. WRITE 'This is a statement'.
    or as follows:
    PROGRAM
    TEST.
    WRITE
    'This is a statement'.
    Use this free formatting to make your programs easier to understand.
    Special Case: Text Literals
    Text literals are sequences of alphanumeric characters in the program code that are enclosed in quotation marks. If a text literal in an ABAP statement extends across more than one line, the following difficulties can occur:
    All spaces between the quotation marks are interpreted as belonging to the text literal. Letters in text literals in a line that is not concluded with quotation marks are interpreted by the editor as uppercase. If you want to enter text literals that do not fit into a single line, you can use the ‘&’ character to combine a succession of text literals into a single one.
    The program fragment
    PROGRAM TEST.
    WRITE 'This
    is
    a statement'.
    inserts all spaces between the quotation marks into the literal, and converts the letters to uppercase.
    This program fragment
    PROGRAM TEST.
    WRITE 'This' &
    ' is ' &
    'a statement'.
    combines three text literals into one.
    Chained Statements
    The ABAP programming language allows you to concatenate consecutive statements with an identical first part into a chain statement.
    To concatenate a sequence of separate statements, write the identical part only once and place a colon ( after it. After the colon, write the remaining parts of the individual statements, separating them with commas. Ensure that you place a period (.) after the last part to inform the system where the chain ends.
    Statement sequence:
    WRITE SPFLI-CITYFROM.
    WRITE SPFLI-CITYTO.
    WRITE SPFLI-AIRPTO.
    Chain statement:
    WRITE: SPFLI-CITYFROM, SPFLI-CITYTO, SPFLI-AIRPTO.
    In the chain, a colon separates the beginning of the statement from the variable parts. After the colon or commas, you can insert any number of spaces.
    You could, for example, write the same statement like this:
    WRITE: SPFLI-CITYFROM,
    SPFLI-CITYTO,
    SPFLI-AIRPTO.
    In a chain statement, the first part (before the colon) is not limited to the keyword of the statements.
    Statement sequence:
    SUM = SUM + 1.
    SUM = SUM + 2.
    SUM = SUM + 3.
    SUM = SUM + 4.
    Chain statement:
    SUM = SUM + : 1, 2, 3, 4.
    Comments
    Comments are texts that you can write between the statements of your ABAP program to explain their purpose to a reader. Comments are distinguished by the preceding signs * (at the beginning of a line) and " (at any position in a line). If you want the entire line to be a comment, enter an asterisk (*) at the beginning of the line. The system then ignores the entire line when it generates the program. If you want part of a line to be a comment, enter a double quotation mark (") before the comment. The system interprets comments indicated by double quotation marks as spaces.
    PROGRAM SAPMTEST *
    WRITTEN BY KARL BYTE, 06/27/1995 *
    LAST CHANGED BY RITA DIGIT, 10/01/1995 *
    TASK: DEMONSTRATION *
    PROGRAM SAPMTEST.
    DECLARATIONS *
    DATA: FLAG " GLOBAL FLAG
    NUMBER TYPE I " COUNTER
    PROCESSING BLOCKS *
    Advantages of ABAP over Contemporary languages
    ABAP OBJECTS
    Object orientation in ABAP is an extension of the ABAP language that makes available the advantages of object-oriented programming, such as encapsulation, interfaces, and inheritance. This helps to simplify applications and make them more controllable.
    ABAP Objects is fully compatible with the existing language, so you can use existing statements and modularization units in programs that use ABAP Objects, and can also use ABAP Objects in existing ABAP programs.
    ABAP Statements – an Overview
    The first element of an ABAP statement is the ABAP keyword. This determines the category of the statement. The different statement categories are as follows:
    Declarative Statements
    These statements define data types or declare data objects which are used by the other statements in a program or routine. The collected declarative statements in a program or routine make up its declaration part.
    Examples of declarative keywords:
    TYPES, DATA, TABLES
    Modularization Statements
    These statements define the processing blocks in an ABAP program.
    The modularization keywords can be further divided into:
    · Defining keywords
    You use statements containing these keywords to define subroutines, function modules, dialog modules and methods. You conclude these processing blocks using the END statements.
    Examples of definitive keywords:
    METHOD ... ENDMETHOD, FUNCTION ... ENDFUNCTION, MODULE ... ENDMODULE.
    · Event keywords
    You use statements containing these keywords to define event blocks. There are no special statements to conclude processing blocks - they end when the next processing block is introduced.
    Examples of event key words:
    AT SELECTION SCREEN, START-OF-SELECTION, AT USER-COMMAND
    Control Statements
    You use these statements to control the flow of an ABAP program within a processing block according to certain conditions.
    Examples of control keywords:
    IF, WHILE, CASE
    Call Statements
    You use these statements to call processing blocks that you have already defined using modularization statements. The blocks you call can either be in the same ABAP program or in a different program.
    Examples of call keywords:
    CALL METHOD, CALL TRANSACTION, SUBMIT, LEAVE TO
    Operational Statements These keywords process the data that you have defined using declarative statements.
    Examples of operational keywords:
    MOVE, ADD
    Unique Concept of Internal Table in ABAP
    Internal tables provide a means of taking data from a fixed structure and storing it in working memory in ABAP. The data is stored line by line in memory, and each line has the same structure. In ABAP, internal tables fulfill the function of arrays. Since they are dynamic data objects, they save the programmer the task of dynamic memory management in his or her programs. You should use internal tables whenever you want to process a dataset with a fixed structure within a program. A particularly important use for internal tables is for storing and formatting data from a database table within a program. They are also a good way of including very complicated data structures in an ABAP program.
    Like all elements in the ABAP type concept, internal tables can exist both as data types and as data objects A data type is the abstract description of an internal table, either in a program or centrally in the ABAP Dictionary, that you use to create a concrete data object. The data type is also an attribute of an existing data object.
    Internal Tables as Data Types
    Internal tables and structures are the two structured data types in ABAP. The data type of an internal table is fully specified by its line type, key, and table type.
    Line type
    The line type of an internal table can be any data type. The data type of an internal table is normally a structure. Each component of the structure is a column in the internal table. However, the line type may also be elementary or another internal table.
    Key
    The key identifies table rows. There are two kinds of key for internal tables - the standard key and a user-defined key. You can specify whether the key should be UNIQUE or NON-UNIQUE. Internal tables with a unique key cannot contain duplicate entries. The uniqueness depends on the table access method.
    If a table has a structured line type, its default key consists of all of its non-numerical columns that are not references or themselves internal tables. If a table has an elementary line type, the default key is the entire line. The default key of an internal table whose line type is an internal table, the default key is empty.
    The user-defined key can contain any columns of the internal table that are not references or themselves internal tables. Internal tables with a user-defined key are called key tables. When you define the key, the sequence of the key fields is significant. You should remember this, for example, if you intend to sort the table according to the key.
    Table type
    The table type determines how ABAP will access individual table entries. Internal tables can be divided into three types:
    Standard tables have an internal linear index. From a particular size upwards, the indexes of internal tables are administered as trees. In this case, the index administration overhead increases in logarithmic and not linear relation to the number of lines. The system can access records either by using the table index or the key. The response time for key access is proportional to the number of entries in the table. The key of a standard table is always non-unique. You cannot specify a unique key. This means that standard tables can always be filled very quickly, since the system does not have to check whether there are already existing entries.
    Sorted tables are always saved sorted by the key. They also have an internal index. The system can access records either by using the table index or the key. The response time for key access is logarithmically proportional to the number of table entries, since the system uses a binary search. The key of a sorted table can be either unique or non-unique. When you define the table, you must specify whether the key is to be unique or not. Standard tables and sorted tables are known generically as index tables.
    Hashed tables have no linear index. You can only access a hashed table using its key. The response time is independent of the number of table entries, and is constant, since the system access the table entries using a hash algorithm. The key of a hashed table must be unique. When you define the table, you must specify the key as UNIQUE.
    Generic Internal Tables
    Unlike other local data types in programs, you do not have to specify the data type of an internal table fully. Instead, you can specify a generic construction, that is, the key or key and line type of an internal table data type may remain unspecified. You can use generic internal tables to specify the types of field symbols and the interface parameters of procedures . You cannot use them to declare data objects.
    Internal Tables as Dynamic Data Objects
    Data objects that are defined either with the data type of an internal table, or directly as an internal table, are always fully defined in respect of their line type, key and access method. However, the number of lines is not fixed. Thus internal tables are dynamic data objects, since they can contain any number of lines of a particular type. The only restriction on the number of lines an internal table may contain are the limits of your system installation. The maximum memory that can be occupied by an internal table (including its internal administration) is 2 gigabytes. A more realistic figure is up to 500 megabytes. An additional restriction for hashed tables is that they may not contain more than 2 million entries. The line types of internal tables can be any ABAP data types - elementary, structured, or internal tables. The individual lines of an internal table are called table lines or table entries. Each component of a structured line is called a column in the internal table.
    Choosing a Table Type
    The table type (and particularly the access method) that you will use depends on how the typical internal table operations will be most frequently executed.
    Standard tables
    This is the most appropriate type if you are going to address the individual table entries using the index. Index access is the quickest possible access. You should fill a standard table by appending lines (ABAP APPEND statement), and read, modify and delete entries by specifying the index (INDEX option with the relevant ABAP command). The access time for a standard table increases in a linear relationship with the number of table entries. If you need key access, standard tables are particularly useful if you can fill and process the table in separate steps. For example, you could fill the table by appending entries, and then sort it. If you use the binary search option with key access, the response time is logarithmically proportional to the number of table entries.
    Sorted tables
    This is the most appropriate type if you need a table which is sorted as you fill it. You fill sorted tables using the INSERT statement. Entries are inserted according to the sort sequence defined through the table key. Any illegal entries are recognized as soon as you try to add them to the table. The response time for key access is logarithmically proportional to the number of table entries, since the system always uses a binary search. Sorted tables are particularly useful for partially sequential processing in a LOOP if you specify the beginning of the table key in the WHERE condition.
    Hashed tables
    This is the most appropriate type for any table where the main operation is key access. You cannot access a hashed table using its index. The response time for key access remains constant, regardless of the number of table entries. Like database tables, hashed tables always have a unique key. Hashed tables are useful if you want to construct and use an internal table which resembles a database table or for processing large amounts of data.
    Advanced Topics
    Batch Input: Concepts
    Processing Sessions
    The above figure shows how a batch input session works.A batch input session is a set of one or more calls to transactions along with the data to be processed by the transactions. The system normally executes the transactions in a session non-interactively, allowing rapid entry of bulk data into an R/3 System.
    A session records transactions and data in a special format that can be interpreted by the R/3 System. When the System reads a session, it uses the data in the session to simulate on-line entry of transactions and data. The System can call transactions and enter data using most of the facilities that are available to interactive users.
    For example, the data that a session enters into transaction screens is subject to the same consistency checking as in normal interactive operation. Further, batch input sessions are subject to the user-based authorization checking that is performed by the system.
    Advantages of ABAP over Contemporary languages
    ABAP Objects offers a number of advantages, even if you want to continue using procedural programming. If you want to use new ABAP features, you have to use object-oriented interfaces anyway.
    Sharing Data: With ABAP shared objects, you can aggregate data once at a central location and the different users and programs can then access this data without the need for copying.
    Exception Handling: With the class-based exception concept of ABAP, you can define a special control flow for a specific error situation and provide the user with information about the error.
    Developing Persistency: For permanent storage of data in ABAP, you use relational database tables by means of database-independent Open SQL, which is integrated in ABAP. However, you can also store selected objects transparently or access the integrated database or other databases using proprietary SQL.
    Connectivity and Interoperability: The Exchange Infrastructure and Web services are the means by which developers can implement a service-oriented architecture. With Web services, you can provide and consume services independently of implementation or protocol. Furthermore, you can do so within NetWeaver and in the communication with other systems. With the features of the Exchange Infrastructure, you can enable, manage, and adapt integration scenarios between systems.
    Making Enhancements: With the Enhancement Framework, you can enhance programs, function modules, and global classes without modification as well as replace existing code. The Switch Framework enables you activate only specific development objects or enhancements in a system.
    Considerable Aspects
    It follows a list of aspects to be considered during development. The list of course is not complete.
    Dynpro persistence
    When implementing dynpros one has to care for himself to read out and persist the necessary fields. Recently it happened to me that I forgot to include a field into the UPDATE-clause which is an error not so easy to uncover if you have other problems to be solved in the same package. Here, tool-support or built-in mechanisms would help.
    The developer could help himself out by creating something like a document containing a cookbook or guide in which parts of a dynpro logic one has to care about persistence. With that at hand, it would be quite easy finding those bugs in short time. Maybe a report scanning for the definition of the dynpro fields to be persisted could scan the code automatically, too.
    Memory Cache
    It should be common-sense that avoiding select-statements onto the database helps reducing the server load. For that the programmer either can resort to function modules if available. This maybe is the case for important tables. Or the programmer needs to implement his own logic using internal tables. Here, the standard software package could provide the developer with a tool or a mechanism auto-generating memory cached tables resp. function modules implementing this.
    Sometimes buffering of database tables could be used, if applicable. But that would require an effort in customizing the system and could drain down system performance overall, especially if a table is involved that has a central role.
    Interfaces
    It should be noticed that some function modules available have an incomplete interface. That means, the interface does not include all parameters evaluated by the logic of the function module. For example, global variables from within the function group could be read out, which cannot be influenced by the general caller. Or memory parameters are used internally to feed the logic with further information.
    One workaround here would be copying the relevant parts of the logic to a newly created function module and then adapt it to the own context. This sometimes is possible, maybe if the copied code is not too lengthy and only a few or no calls to other logic is part of it.
    A modification of the SAP code could be considered, if the modification itself is unavoidable (or another solution would be not justifiable by estimated effort to spend on it) and if the location of the modification seems quite safe against future upgrades or hot fixes. The latter is something that could be evaluated by contacting the SAP hotline or working with OSS message (searching thru existing one, perhaps open a new one).
    Example
    'From SAP NetWeaver:'
    set an exclusive lock at level object-type & object-id
    IF NOT lf_bapi_error = true.
    IF ( NOT istourhd-doc_type IS INITIAL ) AND
    ( NOT istourhd-doc_id IS INITIAL )
    CALL FUNCTION 'ENQUEUE_/DSD/E_HH_RAREF'
    EXPORTING
    obj_typ = istourhd-doc_type
    obj_id = istourhd-doc_id
    EXCEPTIONS
    foreign_lock = 1
    system_failure = 2
    OTHERS = 3.
    IF sy-subrc <> 0.
    terminate processing...
    lf_bapi_error = true.—
    ...and add message to return table
    PERFORM set_msg_to_bapiret2
    USING sy-msgid gc_abort sy-msgno
    sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4
    gc_istourhd gc_enqueue_refdoc space
    CHANGING lt_return.
    ENDIF.
    ENDIF.
    ENDIF. " bapi error
    Example Report(Type - ALV(Advanced List Viewer))
    REPORT Z_ALV_SIMPLE_EXAMPLE_WITH_ITAB .
    *Simple example to use ALV and to define the ALV data in an internal
    *table
    *data definition
    tables:
    marav. "Table MARA and table MAKT
    Data to be displayed in ALV
    Using the following syntax, REUSE_ALV_FIELDCATALOG_MERGE can auto-
    matically determine the fieldstructure from this source program
    Data:
    begin of imat occurs 100,
    matnr like marav-matnr, "Material number
    maktx like marav-maktx, "Material short text
    matkl like marav-matkl, "Material group (so you can test to make
    " intermediate sums)
    ntgew like marav-ntgew, "Net weight, numeric field (so you can test to
    "make sums)
    gewei like marav-gewei, "weight unit (just to be complete)
    end of imat.
    Other data needed
    field to store report name
    data i_repid like sy-repid.
    field to check table length
    data i_lines like sy-tabix.
    Data for ALV display
    TYPE-POOLS: SLIS.
    data int_fcat type SLIS_T_FIELDCAT_ALV.
    select-options:
    s_matnr for marav-matnr matchcode object MAT1.
    start-of-selection.
    read data into table imat
    select * from marav
    into corresponding fields of table imat
    where
    matnr in s_matnr.
    Check if material was found
    clear i_lines.
    describe table imat lines i_lines.
    if i_lines lt 1.
    Using hardcoded write here for easy upload
    write: /
    'No materials found.'.
    exit.
    endif.
    end-of-selection.
    To use ALV, we need a DDIC-structure or a thing called Fieldcatalogue.
    The fieldcatalouge can be generated by FUNCTION
    'REUSE_ALV_FIELDCATALOG_MERGE' from an internal table from any
    report source, including this report.
    Store report name
    i_repid = sy-repid.
    Create Fieldcatalogue from internal table
    CALL FUNCTION 'REUSE_ALV_FIELDCATALOG_MERGE'
    EXPORTING
    I_PROGRAM_NAME = i_repid
    I_INTERNAL_TABNAME = 'IMAT' "capital letters!
    I_INCLNAME = i_repid
    CHANGING
    CT_FIELDCAT = int_fcat
    EXCEPTIONS
    INCONSISTENT_INTERFACE = 1
    PROGRAM_ERROR = 2
    OTHERS = 3.
    *explanations:
    I_PROGRAM_NAME is the program which calls this function
    I_INTERNAL_TABNAME is the name of the internal table which you want
    to display in ALV
    I_INCLNAME is the ABAP-source where the internal table is defined
    (DATA....)
    CT_FIELDCAT contains the Fieldcatalouge that we need later for
    ALV display
    IF SY-SUBRC <> 0.
    write: /
    'Returncode',
    sy-subrc,
    'from FUNCTION REUSE_ALV_FIELDCATALOG_MERGE'.
    ENDIF.
    *This was the fieldcatlogue
    Call for ALV list display
    CALL FUNCTION 'REUSE_ALV_LIST_DISPLAY'
    EXPORTING
    I_CALLBACK_PROGRAM = i_repid
    IT_FIELDCAT = int_fcat
    TABLES
    T_OUTTAB = imat
    EXCEPTIONS
    PROGRAM_ERROR = 1
    OTHERS = 2.
    *explanations:
    I_CALLBACK_PROGRAM is the program which calls this function
    IT_FIELDCAT (just made by REUSE_ALV_FIELDCATALOG_MERGE) contains
    now the data definition needed for display
    I_SAVE allows the user to save his own layouts
    T_OUTTAB contains the data to be displayed in ALV
    IF SY-SUBRC <> 0.
    write: /
    'Returncode',
    sy-subrc,
    'from FUNCTION REUSE_ALV_LIST_DISPLAY'.
    ENDIF.
    OOPs ABAP uses Classes and Interfaces which uses Methods and events.
    If you have Java skills it is advantage for you.
    There are Local classes as well as Global Classes.
    Local classes we can work in SE38 straight away.
    But mostly it is better to use the Global classes.
    Global Classes or Interfaces are to be created in SE24.
    SAP already given some predefined classes and Interfaces.
    This OOPS concepts very useful for writing BADI's also.
    So first create a class in SE 24.
    Define attributes, Methods for that class.
    Define parameters for that Method.
    You can define event handlers also to handle the messages.
    After creation in each method write the code.
    Methods are similar to ABAP PERFORM -FORM statements.
    After the creation of CLass and methods come to SE38 and create the program.
    In the program create a object type ref to that class and with the help of that Object call the methods of that Class and display the data.
    Regards
    Anji

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