ABAP / 4 INTERVIEW QUESTIONS WITH ANSWERS

1) What is SAP R/3?



Ans SAP R/3 refers to Systems Application and Product for data processing Real-time having a 3 tier architecture i.e. Presentation layer, Application layer and Database layer.



2) What are the programming standards followed?



3) What are the contents in technical specifications?



Ans There are five contents in Technical Settings: Data Class, Size Category, Buffering Permission, Buffering Type and Logging.



4) What is an instance?



Ans When you call a function module, an instance of its function group plus its data, is loaded into the memory area of the internal session. An ABAP program can load several instances by calling function modules from different function groups.



5) How to take care of performance in ABAP Development?



6) What is Function group? Difference between function group and function module?



Ans Function Groups act as containers for Function Modules that logically belong together.



Function Groups



1) These cannot be defined in a Function Module.



2) It cannot be called.



3) They are containers for Function Module.







Function Modules







1) These must be defined in a Function Group.



2) It can be called from any program.



3) They are not containers for Function Group.







7) What is the difference between 'Select single * ' and 'Select upto 1 rows'?



Ans ‘Select single *’ – The result of the selection should be a single entry. If it is not possible to identify a unique entry, the system uses the first line of the selection. For e.g.







DATA : ITAB TYPE ZREKHA_EMP.







SELECT SINGLE * FROM ZREKHA_EMP INTO ITAB



WHERE EMPNO = ‘00101’ AND DEPTNO = ‘0010’.







WRITE : / ITAB-EMPNO, ITAB-EMPNAME,ITAB-DEPTNO.







Select upto 1 rows -







8) What Function does data dictionary perform?



Ans Central information repository for application and system data. The ABAP Dictionary contains data definitions (metadata) that allow you to describe all of the data structures in the system (like tables, views, and data types) in one place. This eliminates redundancy.



9) Difference between domain and data element? What are aggregate object?



Ans Domain - Specifies the technical attributes of a data element - its data type, length, possible values, and appearance on the screen. Each data element has an underlying domain. A single domain can be the basis for several data elements. Domains are objects in the ABAP Dictionary.



Data Element - Describes the business function of a table field. Its technical attributes are based on a domain, and its business function is described by its field labels and documentation.



Aggregate Object – Views, Match Code and Lock objects are called aggregate objects because they are formed from several related table.



10) What is view? Different types of view. Explain?



Ans View - A view is a virtual table containing fields from one or more tables. A virtual table that does not contain any data, but instead provides an application-oriented view of one or more ABAP Dictionary tables.



Different Types of View:



1) Maintenance



2) Database – It is on more than two tables.



3) Projection – It is only on one table.



4) Help



11) Can u print decimals in type N? What is difference between float and packed data type?



Ans No, we cannot print decimals in type N because decimal places are not permitted with N



data type.



Float Data Type: It cannot be declared in Parameters.



Packed Number: It can be declared in Parameters. For e.g.



PARAMETERS : A(4) TYPE P DECIMALS 2,



B(4) TYPE P DECIMALS 2.



DATA : C(4) TYPE P DECIMALS 2.



C = A + B.



WRITE : / ‘THE SUM IS’ , C.







12) What is step-loop? Explain all the steps?



Ans A step loop is a repeated series of field-blocks in a screen. Each block can contain one or more fields, and can extend over more than one line on the screen.



Step loops as structures in a screen do not have individual names. The screen can contain more than one step-loop, but if so, you must program the LOOP...ENDLOOPs in the flow logic accordingly. The ordering of the LOOP...ENDLOOPs must exactly parallel the order of the step loops in the screen. The ordering tells the system which loop processing to apply to which loop. Step loops in a screen are ordered primarily by screen row, and secondarily by screen column.



Transaction TZ61 (development class SDWA) implements a step loop version of the table you saw in transaction TZ60.



Static and Dynamic Step Loops



Step loops fall into two classes: static and dynamic. Static step loops have a fixed size that cannot be changed at runtime. Dynamic step loops are variable in size. If the user re-sizes the window, the system automatically increases or decreases the number of step loop blocks displayed. In any given screen, you can define any number of static step loops, but only a single dynamic one.



You specify the class for a step loop in the Screen Painter. Each loop in a screen has the attributes Looptype (fixed=static, variable=dynamic) and Loopcount. If a loop is fixed, the Loopcount tells the number of loop-blocks displayed for the loop. This number can never change.



Programming with static and dynamic step loops is essentially the same. You can use both the LOOP and LOOP AT statements for both types.



Looping in a Step Loop



When you use LOOP AT with a step loop, the system automatically displays the step loop with vertical scroll bars. The scroll bars, and the updated (scrolled) table display, are managed by the system.



Use the following additional parameters if desired:



* FROM and TO

* CURSOR















13) What is the initial value and maximum length of all data type?



Ans







Data Type





Initial field length





Valid field length





Initial value





Meaning

Numeric types



I





4





4





0





Integer (whole number)



F





8





8





0





Floating point number



P





8





1 – 16





0





Packed number

Character types



C





1





1 – 65535





' … '





Text field (alphanumeric characters)



D





8





8





'00000000'





Date field (Format: YYYYMMDD)



N





1





1 – 65535





'0 … 0'





Numeric text field (numeric characters)



T





6





6





'000000'





Time field (format: HHMMSS)

Hexadecimal type



X





1





1 – 65535





X'0 … 0'





Hexadecimal field







14) What are the ways to find out the tables used in the program?



Ans



















15) Can you have two detail lists from the basic list at the same time?



If yes how and if no why?



Ans



















16) What are the different functions used in sap script? What are the parameters used in each Function?



Ans There are three different functions used in SAP Script:







1) OPEN_FORM



2) WRITE_FORM



3) CLOSE_FORM







Parameters in Each Function:







1) OPEN_FORM –



Exporting



Form



Language



2) WRITE_FORM –



Exporting



Element



Window



3) CLOSE_FORM



17) What is sequence of event triggered in report?



Ans There are 6 events in report:







1) Initialization



2) At Selection-Screen



3) Start-of-Selection



4) Get



5) Get Late



6) End-of-Selection



7) Top-of-Page



8) End-of-Page



9) At Line Selection



10) At User Command



11) At PF (nn)







18) What are standard layouts sets in the SAP Script?



Ans There are four standard layouts in the SAP Script:







1) Header



2) Logo



3) Main Window



4) Footer







19) What function module upload data from application server?



Ans



















20) What are the various types of selection screen event?



Ans SELECTION-SCREEN BEGIN OF BLOCK ABC WITH FRAME TITLE T01.





SELECTION-SCREEN BEGIN OF SCREEN 500 AS WINDOW.







CALL SELECTION-SCREEN 500 STARTING AT 10 10.





21) What do you know about a client?



Ans



















22) What are the system fields? Explain?



Ans The ABAP system fields are active in all ABAP programs. They are filled by the runtime environment, and you can query their values in a program to find out particular states of the system. Although they are variables, you should not assign your own values to them, since this may overwrite information that is important for the normal running of the program. However, there are some isolated cases in which you may need to overwrite a system variable. For example, by assigning a new value to the field SY-LSIND, you can control navigation within details lists.







23) What is SAP Script? What is the purpose of SAP Script? Difference between



SAP Script and Report?



Ans SAP Script – It is the integrated text management system of the SAP R/3 System. Two types – PC Editor & Line Editor.







Reports - It is the way to display data fetched from database table onto screen or directly output it to a printer. Two types – Classical and Interactive.







24) What is the use of occurs in internal table? Can u change occurs value in program?



Ans Use of Occurs - If you use the OCCURS parameter, the value of the INITIAL SIZE of the table is returned to the variable







Data : Begin of ITAB occurs 0,







End of ITAB.







Occurs or Initial Size – to specify the initial amount of memory that should be assigned to the table.







Yes, we can change the occurs value in program but output remains the same.







25) Difference between SY-TABIX and SY-INDEX? Where it is used?



Can u check SY-SUBRC after perform?



Ans SY-TABIX - Current line of an internal table. SY-TABIX is set by the statements below, but only for index tables. The field is either not set or is set to 0 for hashed tables.



* APPEND sets SY-TABIX to the index of the last line of the table, that is, it contains the overall number of entries in the table.



* COLLECT sets SY-TABIX to the index of the existing or inserted line in the table. If the table has the type HASHED TABLE, SY-TABIX is set to 0.



* LOOP AT sets SY-TABIX to the index of the current line at the beginning of each loop lass. At the end of the loop, SY-TABIX is reset to the value that it had before entering the loop. It is set to 0 if the table has the type HASHED TABLE.



* READ TABLE sets SY-TABIX to the index of the table line read. If you use a binary search, and the system does not find a line, SY-TABIX contains the total number of lines, or one more than the total number of lines. SY-INDEX is undefined if a linear search fails to return an entry.



* SEARCH FOR sets SY-TABIX to the index of the table line in which the search string is found.



SY_INDEX - In a DO or WHILE loop, SY-INDEX contains the number of loop passes including the current pass.















26) Difference between UPLOAD and WS_UPLOAD?



Ans UPLOAD - File transfer with dialog from presentation server file to internal table. Data which is available in a file on the presentation server is transferred in an internal table. ASCII & Binary files can be transferred.







WS_UPLOAD - To read data from the presentation server into an internal table without a user dialog, use the function module WS_UPLOAD. The most important parameters are listed below.





Parameters Function

CODEPAGE Only for upload under DOS: Value IBM

FILENAME Filename

FILETYPE File type







27) Why did u switch to SAP?



Ans







28) What is a Logical Database?



Ans Logical Databases are special ABAP programs that retrieve data and make it available to application programs.







Use of LDB – is used to read data from database tables by linking them to executable ABAP programs.







29) What are the events used for Logical Database?



Ans Two Events –







1) GET - This is the most important event for executable programs that use a logical database. It occurs when the logical database has read a line from the node and made it available to the program in the work area declared using the statement NODES . The depth to which the logical database is read is determined by the GET statements







2) PUT - The PUT statement directs the program flow according to the structure of



the logical database.







30) What is the difference between Get and Get Late?



Ans GET - After the logical database has read an entry from the node .







GET LATE - After all of the nodes of the logical database have been processed that are below in the database hierarchy.







31) What are the data types of Internal Tables?



Ans There are three types:







1) Line



2) Key



3) Table











32) What are the events used in ABAP in the order of execution?



Ans Events are:







1. INITIALIZATION



2. AT SELECTION-SCREEN



3. AT SELECTION-SCREEN ON



4. START-OF-SELECTION



5. TOP-OF-PAGE



6. TOP-OF-PAGE DURING LINE SELECTION



7. END-OF-PAGE



8. END-OF-SELECTION



9. AT USER-COMMAND



10. AT LINE-SELECTION



11. AT PF



12. GET



13. GET LATE.



14. AT User Command







33) What are Interactive Reports?



Ans An output list which displays just the basic details & allow user to interact, so that a new list is populated based on user-selection. With interactive list, the user can actively control data retrieval and display during the session.







34) What are the commands used for interactive reports?



Ans Top-of-Page during line-selection







35) What are the system fields u have worked with? Explain?



Ans I had worked with the following (30) system fields:







1) SY-DBSYS - Central Database



2) SY-HOST - Server



3) SY-OPSYS - Operating System



4) SY-SAPRL - SAP Release



5) SY-SYSID - System Name



6) SY-LANGU - User Logon Language



7) SY-MANDT - Client



8) SY-UNAME - Logon User Name



9) SY-DATLO - Local Date



10) SY-DATUM - Server Date



11) SY-TIMLO - Local Time



12) SY-UZEIT - Server Time



13) SY-DYNNR - Screen Number



14) SY-REPID - Current ABAP program



15) SY-TCODE - Transaction Code



16) SY-ULINE - Horizontal Line



17) SY-VLINE - Vertical Line



18) SY-INDEX - Number of current loop Pass



19) SY-TABIX - Current line of internal table



20) SY-DBCNT - Number of table entries processed



21) SY-SUBRC - Return Code



22) SY-UCOMM - Function Code



23) SY-LINCT - Page Length of list



24) SY-LINNO - Current Line



25) SY-PAGNO - Current Page Number



26) SY-LSIND - Index of List



27) SY-MSGID - Message Class



28) SY-MSGNO - Message Number



29) SY-MSGTY - Message Type



30) SY-SPONO - Spool number during printing







36) What is the difference between Primary key and Unique Key?



Ans Primary Key – It can accepts 0 value and cannot be NULL.



Unique Key – It can be NULL.







37) What is the transaction code for Table maintenance?



Ans SM30







38) If u are using Logical Databases how will u modify the selection-screen elements?



Ans Select-options : dname for deptt-dname.







39) What is an RFC?



Ans Remote Function Call











40) If u are using RFC and passing values to a remote system how does it work?



Ans







41) What are the events in Screen Programming?



Ans There are two events in Screen Programming:







1. PBO (Process Before Output) – Before the screen is displayed, the PBO event is processed.

2. PAI (Process After Input) – When the user interacts with the screen, the PAI event is processed.

3. POH (Process On Help) - are triggered when the user requests field help (F1). You can program the appropriate coding in the corresponding event blocks. At the end of processing, the system carries on processing the current screen.

4. POV (Process On Value) - are triggered when the user requests possible values help (F4). You can program the appropriate coding in the corresponding event blocks. At the end of processing, the system carries on processing the current screen.











42) What is the significance of HIDE?



Ans Its stores the click value and display the related record in the secondary list.







43) Where do u code the HIDE statement?



Ans In a LOOP statement







44) Types of BDC's?



Ans There are two types of BDC’s:







1) Transaction Method



2) Session Method







45) Advantages & Disadvantages of different types of BDC's?



Ans Transaction Method:







1) It is faster than session method.



2) While executing, it starts from starting.







Session Method:







1) It is slower than transaction method.



2) While executing, it does not start from starting.







46) What are the events used in Interactive Reports.



Ans There are three events of Interactive Reports:







I. At PF(nn)



II. At line-selection



III. At user-command







47) What is an RDBMS?



Ans RDBMS – Relational Database Management System. It helps to create relationship between two or more table.







48) What standards u use to follow while coding ABAP programs?



Ans















49) What will you code in START-OF-SELECTION & END-OF-SELECTON & why?



Ans START-OF-SELECTION







SELECT * FROM DEPTT INTO CORRESPONDING FIELDS OF ITAB



WHERE DEPTNO IN DEPTNO.



APPEND ITAB.



ENDSELECT.







LOOP AT ITAB.



WRITE : / 10 ITAB-DEPTNO.



HIDE : ITAB-DEPTNO.



ENDLOOP.







END-OF-SELECTION







50) What are joins and different types joins?



Ans There are four types of Joins:







1) Self Join



2) Inner Join



3) Outer Join



4) Equi Join







51) Which is the default join?



Ans















52) How do u display a data in a Detail List?



Ans By using two statements:







1) Top-of-page during line-selection



2) At line-selection







53) What are the types of windows in SAP Script?



Ans There are five Standard Layouts in SAP Script:







1) Page



2) Window



3) Page Window



4) Paragraph Format



5) Character Format







54) What are the function modules used in a SAP Script driver program?



Ans There are three functions used in SAP Script:







1) OPEN_FORM



2) WRITE_FORM



3) CLOSE_FORM











55) What are Extracts?



Ans Extracts are dynamic sequential datasets in which different lines can have different structures. We can access the individual records in an extract dataset using a LOOP.







56) How would u go about improving the performance of a Program, which selects data from MSEG & MKPF?



Ans



















57) How does System work in case of an Interactive Report?



Ans



















58) What is LUW?



Ans Logical Unit of Work



















59) Different types of LUWs. What r they?



Ans Two types of LUW are:







1) DB LUW - A database LUW is the mechanism used by the database to ensure that its data is always consistent. A database LUW is an inseparable sequence of database operations that ends with a database commit. The database LUW is either fully executed by the database system or not at all. Once a database LUW has been successfully executed, the database will be in a consistent state. If an error occurs within a database LUW, all of the database changes since the beginning of the database LUW are reversed. This leaves the database in the state it had before the transaction started.



2) SAP LUW - A logical unit consisting of dialog steps, whose changes are written to the database in a single database LUW is called an SAP LUW. Unlike a database LUW, an SAP LUW can span several dialog steps, and be executed using a series of different work processes.







60) What is First event triggered in program?



Ans



















61) What are various Joins? What is right outer join?



Ans















62) How do u find out whether a file exits on the presentation server?



Ans eps_get_directory_listing for directory















63) Systems fields used for Interactive Lists AND Lists



Ans Interactive System Fields: SY-LSIND, SY-CPAGE, SY-LILLI, SY-LISEL, SY-LISTI,



SY-LSTAT, SY-STACO, SY-STARO







Lists: SY-COLNO, SY-LINCT, SY-LINNO, SY-LINSZ, SY-PAGNO,



SY-TVAR0…..SY-TVAR9, SY-WTITL







64) Logo in SAP Script?



Ans RSTXLDMC OR







Steps for making and inserting Logo in SAP Script:







First Procedure:







1) Draw the picture



2) Save it



3) /nSE78



4) Write name & Choose Color



5) Click on Import



6) Browse picture



7) Enter







Second Procedure







1) /nSE71



2) Insert



3) Graphics



4) Click on stored on document server



5) Execute



6) Choose name of BMAP







65) What are the difference between call screen and leave screen?



Ans Call Screen: Calling a single screen is a special case of embedding a screen sequence. If you want to prevent the called screen from covering the current screen completely, you can use the CALL SCREEN statement with the STARTING AT and ENDING AT







CALL SCREEN 1000.







CALL SCREEN 1000 STARTING AT 10 10 ENDING AT 20 20.







LEAVE SCREEN statement ends the current screen and calls the subsequent screen.



LEAVE SCREEN.



LEAVE TO SCREEN 2000.



66) If internal table used in for all entries in empty then what happens



Ans No, records will be displayed.







67) If I forgot some command in SAP Script e.g.: suppress zero display - How to do find it?



Ans Suppressing of entire screens is possible with this command. This command allows us to perform screen processing “in the background”. Suppressing screens is useful when we are branching to list-mode from a transaction dialog step.







68) How to write a BDC - how do u go about it?



Ans Steps for writing BDC







1) /nSE38



2) Declare Tables, Data (for ITAB) and Data (for BDCITAB)



3) Call function ‘Upload’.



4) Write code for the First Screen, Radio Button, Filename, Change Button, Second Screen, Utilities (Create Entries), Third Screen and Save.



5) Call transaction ‘SE11’ using BDCITAB mode ‘A’.



6) Save, Check Errors, Activate and Execute.



















69) What is Performance tuning?



Ans



















70) Define Documentation.



Ans



















71) Brief about Testing of programs.



Ans



















72) How do u move on to the next screen in interactive reporting?



Ans Write code of the following:







1) Top-of-Page during line-selection



2) At line-selection







73) Create any functions? How to go about it?



Ans Steps for creating the Functions:







First Procedure:







1) /nSE37



2) Goto



3) Function Group (FG)



4) Create Group



5) Name of FG (ZREKHA_FG)



6) Short Text



7) Save



8) Local Object







Second Procedure







1) Environment



2) Inactive Object



3) Function Group (ZREKHA_FG)



4) Activate



5) Back







Third Procedure







1) Name of Function Module (ZREKHA_FM)



2) Create



3) Write FG Name (ZREKHA_FG)



4) Short Text



5) Save







Fourth Step:







Call function ‘ZREKHA_FM’.







74) Advanced topics?



Ans



















75) Function modules used in F4 help.



Ans There are two types of function modules used in F4 help:







1) F4IF_FIELD_VALUE_REQUEST



2) F4IF_INT_TABLE_VALUE_REQUEST







76) Work most on which module: Name a few tables.



Ans Sales & Distribution Module







1) Sales Document: Item Data – VBAP



2) Sales Document: Partner – VBPA



3) Sales Document: Header Data – VBAK



4) Sales Document Flow – VBFA



5) Sales Document: Delivery Item Data - LIPS



6) Customer Master – KNA1



7) Material Data – MARA



8) Conditions (Transaction Data) - KONV







77) System Table used



Ans



1) Sales Document: Item Data – VBAP



2) Sales Document: Partner – VBPA



3) Sales Document: Header Data – VBAK



4) Sales Document Flow – VBFA



5) Sales Document: Delivery Item Data - LIPS



6) Customer Master – KNA1



7) Material Data – MARA



8) Conditions (Transaction Data) - KONV











78) From a table how do u find whether a material is used in another material BOM?



Ans



























79) What is read line?



Ans READ LINE and READ CURRENT LINE – These statements are used to read data from the lines of existing list levels. These statements are closely connected to the HIDE technique.







80) How u used logical database? How is data transferred to program? Corresponding statement in LDB.



Ans



















81) How do u suppress fields on selection screen generated by LDB?



Ans



















82) Can there be more than 1 main window in SAP Script?



Ans No, there cannot be more than 1 main window in SAP Script because in WRITE_FORM, it asks for the parameter Window that will create the problem.







WRITE_FORM –



Exporting



Element



Window







83) Global and local data in function modules.



Ans



















84) What are the differences between SAP memory and ABAP memory?



Ans ABAP Memory is a memory area in the internal session (roll area) of an ABAP program. Data within this area is retained within a sequence of program calls, allowing you to pass data between programs that call one another. It is also possible to pass data between sessions using SAP Memory.



SAP Memory is a memory area to which all sessions within a SAPgui have access. You can use SAP memory either to pass data from one program to another within a session (as with ABAP memory) or to pass data from one session to another.



85) What are differences between At selection-screen and At selection-screen output?



Ans AT SELECTION-SCREEN event is triggered in the PAI of the selection screen once the ABAP runtime environment has passed all of the input data from the selection screen to the ABAP program.



AT SELECTION-SCREEN OUTPUT - This event block allows you to modify the selection screen directly before it is displayed.



86) What are the events?



Ans



















87) What is get cursor field?



Ans GET CURSOR statement transfers the name of the screen element on which the cursor is positioned during a user action into the variable .



GET CURSOR FIELD [OFFSET ] [LINE ] [VALUE ] LENGTH ].



88) What is the inside concept in select-options?



Ans Select-options specify are displayed on the selection screen for the user to enter values.







Different Properties of Select-options:







1) Visible Length



2) Matchcode Object



3) Memory ID



4) Lowercase



5) Obligatory



6) No Display



7) Modify ID







89) What is the difference between occurs 1 and occurs 2?



Ans



















90) What is the difference between Free and Refresh?



Ans Free - You can use FREE to initialize an internal table and release its memory space without first using the REFRESH or CLEAR statement. Like REFRESH, FREE works on the table body, not on the table work area. After a FREE statement, you can address the internal table again. It still occupies the amount of memory required for its header (currently 256 bytes). When you refill the table, the system has to allocate new memory space to the lines.







Refresh - This always applies to the body of the table. As with the CLEAR statement, the memory used by the table before you initialized it remains allocated. To release the memory space, use the statement







91) What are elements?



Ans



















92) Can we have more than one selection-screen and how?



Ans Yes, we can have more than one selection screen.







Selection-screen begin of block honey with frame title text-101.



Select-options : deptno for zrekha_deptt-deptno.



Selection-screen end of block honey.







Selection-screen begin of block honey1 with frame title text-102.



Select-options : dname for zrekha_deptt-dname.



Selection-screen end of block honey1.







93) How to declare select-option as a parameter?



Ans SELECT-OPTIONS: specify are displayed on the selection screen for the user to enter values.







Parameters: dname like dept-dname.







Select-options: dname for dept-dname.







94) How can u write programmatically value help to a field without using search help and



match codes?



Ans By using two types of function modules to be called in SAP Script:







1) HELP_OBJECT_SHOW_FOR_FIELD



2) HELP_OBJECT_SHOW







95) What are the differences between SE01, SE09 and SE10?



Ans SE01 - Correction & Transport Organizer



SE09 - Workbench Organizer



SE10 - Customizing Organizer







96) How to set destination?



Ans



























97) What are the function module types?



Ans



















98) What are tables?



Ans Tables : ZREKHA_EMP.







It creates a structure – the table work area in a program for the database tables, views or structure ZREKHA_EMP. The table work area has the same name as the object for which we created it. ZREKHA_EMP must be declared in the ABAP dictionary. The name and sequence of fields in the table work area ZREKHA_EMP corresponds exactly to the sequence of fields in the database table, view definition in the ABAP dictionary.







99) What are client-dependant tables and independent tables?



Ans



















100) How to distinguish client-dependant tables from independent tables?



Ans



















101) What is the use of Table maintenance allowed?



Ans Mark the Table maintenance allowed flag if users with the corresponding authorization may change the data in the table using the Data Browser (Transaction SE16). If the data in the table should only be maintained with programs or with the table view maintenance transaction (Transaction SM30), you should not set the flag.







102) How to define Selection Screen?



Ans Parameters, Select-options & Selection-Screen







103) What are the check tables and value tables?



Ans Check Table: The ABAP Dictionary allows you to define relationships between tables using foreign keys . A dependent table is called a foreign key table, and the referenced table is called the check table. Each key field of the check table corresponds to a field in the foreign key table. These fields are called foreign key fields. One of the foreign key fields is designated as the check field for checking the validity of values. The key fields of the check table can serve as input help for the check field.



Value Table: Prior to Release 4.0, it was possible to use the value table of a domain to provide input help. This is no longer possible, primarily because unexpected results could occur if the value table had more than one key field. It was not possible to restrict the other key fields, which meant that the environment of the field was not considered, as is normal with check tables.



In cases where this kind of value help was appropriate, you can reconstruct it by creating a search help for the data elements that use the domain in question, and using the value table as the selection method.



Check table will be at field level checking.



Value table will be at domain level checking ex: scarr table is check table for carrid.



104) What is the difference between tables and structures?



Ans Tables:



1) Data is permanently stored in tables in the database.



2) Database tables are generated from them.



















Structure:



1) It contains data temporarily during program run-time.



2) No Database tables are generated from it.







105) How to declare one internal table without header line without using structures?



Ans No, we cannot declare internal table without header line and without structure because it gives error “ITAB cannot be a table, a reference, a string or contain any of these object”.







Code with Header without Structure







TABLES : ZREKHA_EMP.



DATA : ITAB LIKE ZREKHA_EMP OCCURS 0 WITH HEADER LINE.







SELECT * FROM ZREKHA_EMP INTO CORRESPONDING FIELDS OF ITAB.



APPEND ITAB.



ENDSELECT.







LOOP AT ITAB.



WRITE : / ITAB-EMPNO, ITAB-EMPNAME,ITAB-DEPTNO.



ENDLOOP.







Code without Header with Structure







TABLES : ZREKHA_EMP.







DATA : BEGIN OF ITAB OCCURS 0,



EMPNO LIKE XREKHA_EMP-EMPNO,



EMPNAME LIKE XREKHA_EMP-EMPNAME,



DEPTNO LIKE XREKHA_EMP-DEPTNO,



END OF ITAB.







SELECT * FROM ZREKHA_EMP INTO CORRESPONDING FIELDS OF ITAB.



APPEND ITAB.



ENDSELECT.







LOOP AT ITAB.



WRITE : / ITAB-EMPNO, ITAB-EMPNAME,ITAB-DEPTNO.



ENDLOOP.







106) What are lock objects?



Ans Reason for Setting Lock: Suppose a travel agent want to book a flight. The customer wants to fly to a particular city with a certain airline on a certain day. The booking must only be possible if there are still free places on the flight. To avoid the possibility of overbooking, the database entry corresponding to the flight must be locked against access from other transactions. This ensures that one user can find out the number of free places, make the booking, and change the number of free places without the data being changed in the meantime by another transaction.



The R/3 System synchronizes simultaneous access of several users to the same data records with a lock mechanism. When interactive transactions are programmed, locks are set and released by calling function modules (see Function Modules for Lock Requests). These function modules are automatically generated from the definition of lock objects in the ABAP Dictionary.



Two types of Lock: Shared and Exclusive







107) What are datasets? What are the different syntaxes?



Ans The sequential files (ON APPLICATION SERVER) are called datasets. They are used for file handling in SAP.







OPEN DATASET [DATASET NAME] FOR [OUTPUT / INPUT / APPENDING]



IN [BINARY / TEXT] MODE



AT POSITION [POSITION]



MESSAGE [FIELD]







READ DATASET [DATASET NAME] INTO [FIELD]







DELETE DATASET [DATASET NAME]







CLOSE DATASET [DATASET NAME]







TRANSFER [FIELD] TO [DATASET NAME]







108) What are the events we use in dialog programming and explain them?



Ans There are two events in Dialog Programming i.e. screen:







1. PBO (Process Before Output) – Before the screen is displayed, the PBO event is processed.

2. PAI (Process After Input) – When the user interacts with the screen, the PAI event is processed.

3. POH (Process On Help) - are triggered when the user requests field help (F1). You can program the appropriate coding in the corresponding event blocks. At the end of processing, the system carries on processing the current screen.

4. POV (Process On Value) - are triggered when the user requests possible values help (F4). You can program the appropriate coding in the corresponding event blocks. At the end of processing, the system carries on processing the current screen.











109) What is the difference between OPEN_FORM and CLOSE_FORM?



Ans OPEN_FORM – This module opens layout set printing. This function must be called up before we can work with other layout set function like WRITE_FORM.







WRITE_FORM – Output text element in form window. The specified element of the layout set window entered is output. The element must be defined in the layout set.







CLOSE_FORM – End layout set printing. Form printing started with OPEN_FORM is completed. Possible closing operations on the form last opened are carried out. Form printing must be completed by this function module. If this is not carried out, nothing is printed or displayed on the screen.











110) What are the page windows? How many main windows will be there in a page window?



Ans Page Window: In this window, we define the margins for left, width, upper and height for the layout of Header, Logo, Main, & Footer.















111) What are control events in a loop?



Ans Control level processing is allowed within a LOOP over an internal table. This means that we can divide sequences of entries into groups based on the contents of certain fields.



AT .



ENDAT.



You can react to the following control level changes:

Meaning

FIRST First line of the internal table

LAST Last line of the internal table

NEW Beginning of a group of lines with the same contents in the field and in the fields left of

END Of End of a group of lines with the same contents in the field and in the fields left of







112) How to debugg a script?



Ans Go to SE71, give layout set name, go to utilities select debugger mode on.







113) How many maximum sessions can be open in SAPgui?



Ans There are maximum 6 sessions open in SAPgui.







114) SAP Scripts and ABAP programs are client dependent or not? Why?



Ans







115) What are System Variable?



Ans System variables have been predefined by SAP. We can use these variables in formulas or, for example, to pass on certain pieces of information to a function module. How the function called by the function module behaves depends on the type of information passed on.



At present, we can use the following system variables:

System Variable Use Meaning

SY_MODE In function modules Current mode of the PI sheet

SY_TEST In function modules Status of the PI sheet (test or active)

SY_ROW In function modules Current table line

SY_VALUE or X Generally Refers to the immediately preceding input value







116) Is it compulsory to use all the events in Reports?



Ans



















117) What is the difference between sum and collect?



Ans Sum: You can only use this statement within a LOOP. If you use SUM in an AT - ENDAT block, the system calculates totals for the numeric fields of all lines in the current line group and writes them to the corresponding fields in the work area. If you use the SUM statement outside an AT - ENDAT block (single entry processing), the system calculates totals for the numeric fields of all lines of the internal table in each loop pass and writes them to the corresponding fields of the work area. It therefore only makes sense to use the SUM statement in AT...ENDAT blocks.



If the table contains a nested table, you cannot use the SUM statement. Neither can you use it if you are using a field symbol instead of a work area in the LOOP statement.



Collect:







118) What are session method and call transaction method and explain about them?



Ans Session method – Use the BDC_OPEN_GROUP to create a session. Once we have created a session, then we can insert the batch input data into it with BDC_INSERT. Use the BDC_INSERT to add a transaction to a batch input session. We specify the transaction that is to be started in the call to BDC_INSERT. We must provide a BDCDATA structure that contains all the data required to process the transaction completely. Use the BDC_CLOSE_GROUP to close a session after we have inserted all of our batch input data into it. Once a session is closed, it can be processed.







Call Transaction -



In this method, we use CALL TRANSACTION USING to run an SAP transaction. External data does not have to be deposited in a session for later processing. Instead, the entire batch input process takes place inline in our program.







119) If you have 10000 records in your file, which method you use in BDC?



Ans Call transaction is faster then session method. But usually we use session method in real time...because we can transfer large amount of data from internal table to database and if any errors in a session, then process will not complete until session get correct.







120) What are different modes of Call Transaction method and explain them?



Ans There are three modes of Call Transaction method:







1) A – Display All Screens



2) E – Display Errors



3) N – Background Processing



--------------------------------------------------------------------------------------------------------------------









121) What is the typical structure of an ABAP program?



Ans HEADER, BODY, FOOTER.







122) What are field symbols and field groups? Have you used "component idx of structure" clause with field groups?



Ans Field Symbols – They are placeholder or symbolic names for the other fields. They do not physically reserve space for a field, but point to its contents. It can point to any data objects.







Field-symbols







Field Groups – Field groups does not reserve storage space but contains pointers to existing fields.







An extract dataset consists of a sequence of records. These records may have different structures. All records with the same structure form a record type. You must define each record type of an extract dataset as a field group, using the FIELD-GROUPS statement.







Field-groups







123) What should be the approach for writing a BDC program?



Ans STEP 1: CONVERTING THE LEGACY SYSTEM DATA TO A FLAT FILE



to internal table CALLED "CONVERSION".







STEP 2: TRANSFERING THE FLAT FILE INTO SAP SYSTEM CALLED



"SAP DATA TRANSFER".







STEP 3: DEPENDING UPON THE BDC TYPE







i) Call transaction (Write the program explicitly)



ii) Create sessions (sessions are created and processed. If success, data will transfer).







124) What is a batch input session?



Ans BATCH INPUT SESSION is an intermediate step between internal table and database table. Data along with the action is stored in session i.e. data for screen fields, to which screen it is passed, program name behind it, and how next screen is processed.







Create session – BDC_OPEN_GROUP



Insert batch input – BDC_INSERT



Close session – BDC_CLOSE_GROUP







125) What is the alternative to batch input session?



Ans Call Transaction Method & Call Dialog







126) A situation: An ABAP program creates a batch input session. We need to submit the



program and the batch session in background. How to do it?



Ans Go to SM36 and create background job by giving job name, job class and job steps



(JOB SCHEDULING)















127) What is the difference between a pool table and a transparent table and how they are



stored at the database level?



Ans Pool Table -







1) Many to One Relationship.



2) Table in the Dictionary has the different name, different number of fields, and the fields have the different name as in the R3 Table definition.



3) It can hold only pooled tables.







Transparent Table –



1) One to One relationship.



2) Table in the Dictionary has the same name, same number of fields, and the fields have the same name as in the R3 Table definition.



3) It can hold Application data.



128) What are the problems in processing batch input sessions? How is batch input process



different from processing on line?



Ans Two Problems: -







1) If the user forgets to opt for keep session then the session will be automatically removed from the session queue (log remains). However, if session is processed we may delete it manually.



2) If session processing fails, data will not be transferred to SAP database table.







129) Is Session Method, Asynchronous or Synchronous?



Ans Synchronous

Saturday, 31 January 2009

Interview Questions on Java

What if the main method is declared as private?

The program compiles properly but at runtime it will give “Main method not public.” message.

What is meant by pass by reference and pass by value in Java?

Pass by reference means, passing the address itself rather than passing the value. Pass by value means passing a copy of the value.

If you’re overriding the method equals() of an object, which other method you might also consider?

hashCode()

What is Byte Code?

Or

What gives java it’s “write once and run anywhere” nature?

All Java programs are compiled into class files that contain bytecodes. These byte codes can be run in any platform and hence java is said to be platform independent.

Expain the reason for each keyword of public static void main(String args[])?

public- main(..) is the first method called by java environment when a program is executed so it has to accessible from java environment. Hence the access specifier has to be public.

static: Java environment should be able to call this method without creating an instance of the class , so this method must be declared as static.

void: main does not return anything so the return type must be void

The argument String indicates the argument type which is given at the command line and arg is an array for string given during command line.

What are the differences between == and .equals() ?

Or

what is difference between == and equals

Or

Difference between == and equals method

Or

What would you use to compare two String variables - the operator == or the method equals()?

Or

How is it possible for two String objects with identical values not to be equal under the == operator?

The == operator compares two objects to determine if they are the same object in memory i.e. present in the same memory location. It is possible for two String objects to have the same value, but located in different areas of memory.

== compares references while .equals compares contents. The method public boolean equals(Object obj) is provided by the Object class and can be overridden. The default implementation returns true only if the object is compared with itself, which is equivalent to the equality operator == being used to compare aliases to the object. String, BitSet, Date, and File override the equals() method. For two String objects, value equality means that they contain the same character sequence. For the Wrapper classes, value equality means that the primitive values are equal.

public class EqualsTest {

public static void main(String[] args) {

String s1 = “abc”;
String s2 = s1;
String s5 = “abc”;
String s3 = new String(”abc”);
String s4 = new String(”abc”);
System.out.println(”== comparison : ” + (s1 == s5));
System.out.println(”== comparison : ” + (s1 == s2));
System.out.println(”Using equals method : ” + s1.equals(s2));
System.out.println(”== comparison : ” + s3 == s4);
System.out.println(”Using equals method : ” + s3.equals(s4));
}
}

Output
== comparison : true
== comparison : true
Using equals method : true
false
Using equals method : true

What if the static modifier is removed from the signature of the main method?

Or

What if I do not provide the String array as the argument to the method?

Program compiles. But at runtime throws an error “NoSuchMethodError”.

Why oracle Type 4 driver is named as oracle thin driver?

Oracle provides a Type 4 JDBC driver, referred to as the Oracle “thin” driver. This driver includes its own implementation of a TCP/IP version of Oracle’s Net8 written entirely in Java, so it is platform independent, can be downloaded to a browser at runtime, and does not require any Oracle software on the client side. This driver requires a TCP/IP listener on the server side, and the client connection string uses the TCP/IP port address, not the TNSNAMES entry for the database name.

What is the difference between final, finally and finalize? What do you understand by the java final keyword?

Or

What is final, finalize() and finally?

Or

What is finalize() method?

Or

What is the difference between final, finally and finalize?

Or

What does it mean that a class or member is final?

o final - declare constant
o finally - handles exception
o finalize - helps in garbage collection

Variables defined in an interface are implicitly final. A final class can’t be extended i.e., final class may not be subclassed. This is done for security reasons with basic classes like String and Integer. It also allows the compiler to make some optimizations, and makes thread safety a little easier to achieve. A final method can’t be overridden when its class is inherited. You can’t change value of a final variable (is a constant). finalize() method is used just before an object is destroyed and garbage collected. finally, a key word used in exception handling and will be executed whether or not an exception is thrown. For example, closing of open connections is done in the finally method.

What is the Java API?

The Java API is a large collection of ready-made software components that provide many useful capabilities, such as graphical user interface (GUI) widgets.

What is the GregorianCalendar class?

The GregorianCalendar provides support for traditional Western calendars.

What is the ResourceBundle class?

The ResourceBundle class is used to store locale-specific resources that can be loaded by a program to tailor the program’s appearance to the particular locale in which it is being run.

Why there are no global variables in Java?

Global variables are globally accessible. Java does not support globally accessible variables due to following reasons:

* The global variables breaks the referential transparency
* Global variables creates collisions in namespace.

How to convert String to Number in java program?

The valueOf() function of Integer class is is used to convert string to Number. Here is the code example:
String numString = “1000″;
int id=Integer.valueOf(numString).intValue();

What is the SimpleTimeZone class?

The SimpleTimeZone class provides support for a Gregorian calendar.

What is the difference between a while statement and a do statement?

A while statement (pre test) checks at the beginning of a loop to see whether the next loop iteration should occur. A do while statement (post test) checks at the end of a loop to see whether the next iteration of a loop should occur. The do statement will always execute the loop body at least once.

What is the Locale class?

The Locale class is used to tailor a program output to the conventions of a particular geographic, political, or cultural region.

Describe the principles of OOPS.

There are three main principals of oops which are called Polymorphism, Inheritance and Encapsulation.

Explain the Inheritance principle.

Inheritance is the process by which one object acquires the properties of another object. Inheritance allows well-tested procedures to be reused and enables changes to make once and have effect in all relevant places

What is implicit casting?

Implicit casting is the process of simply assigning one entity to another without any transformation guidance to the compiler. This type of casting is not permitted in all kinds of transformations and may not work for all scenarios.

Example

int i = 1000;

long j = i; //Implicit casting

Is sizeof a keyword in java?

The sizeof operator is not a keyword.

What is a native method?

A native method is a method that is implemented in a language other than Java.

In System.out.println(), what is System, out and println?

System is a predefined final class, out is a PrintStream object and println is a built-in overloaded method in the out object.

What are Encapsulation, Inheritance and Polymorphism

Or

Explain the Polymorphism principle. Explain the different forms of Polymorphism.

Polymorphism in simple terms means one name many forms. Polymorphism enables one entity to be used as a general category for different types of actions. The specific action is determined by the exact nature of the situation.

Polymorphism exists in three distinct forms in Java:
• Method overloading
• Method overriding through inheritance
• Method overriding through the Java interface

What is explicit casting?

Explicit casting in the process in which the complier are specifically informed to about transforming the object.

Example

long i = 700.20;

int j = (int) i; //Explicit casting

What is the Java Virtual Machine (JVM)?

The Java Virtual Machine is software that can be ported onto various hardware-based platforms

What do you understand by downcasting?

The process of Downcasting refers to the casting from a general to a more specific type, i.e. casting down the hierarchy

What are Java Access Specifiers?

Or

What is the difference between public, private, protected and default Access Specifiers?

Or

What are different types of access modifiers?

Access specifiers are keywords that determine the type of access to the member of a class. These keywords are for allowing
privileges to parts of a program such as functions and variables. These are:
• Public : accessible to all classes
• Protected : accessible to the classes within the same package and any subclasses.
• Private : accessible only to the class to which they belong
• Default : accessible to the class to which they belong and to subclasses within the same package

Which class is the superclass of every class?

Object.

Name primitive Java types.

The 8 primitive types are byte, char, short, int, long, float, double, and boolean.

What is the difference between static and non-static variables?

Or

What are class variables?

Or

What is static in java?

Or

What is a static method?

A static variable is associated with the class as a whole rather than with specific instances of a class. Each object will share a common copy of the static variables i.e. there is only one copy per class, no matter how many objects are created from it. Class variables or static variables are declared with the static keyword in a class. These are declared outside a class and stored in static memory. Class variables are mostly used for constants. Static variables are always called by the class name. This variable is created when the program starts and gets destroyed when the programs stops. The scope of the class variable is same an instance variable. Its initial value is same as instance variable and gets a default value when its not initialized corresponding to the data type. Similarly, a static method is a method that belongs to the class rather than any object of the class and doesn’t apply to an object or even require that any objects of the class have been instantiated.
Static methods are implicitly final, because overriding is done based on the type of the object, and static methods are attached to a class, not an object. A static method in a superclass can be shadowed by another static method in a subclass, as long as the original method was not declared final. However, you can’t override a static method with a non-static method. In other words, you can’t change a static method into an instance method in a subclass.

Non-static variables take on unique values with each object instance.

What is the difference between the boolean & operator and the && operator?

If an expression involving the boolean & operator is evaluated, both operands are evaluated, whereas the && operator is a short cut operator. When an expression involving the && operator is evaluated, the first operand is evaluated. If the first operand returns a value of true then the second operand is evaluated. If the first operand evaluates to false, the evaluation of the second operand is skipped.

How does Java handle integer overflows and underflows?

It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.

What if I write static public void instead of public static void?

Program compiles and runs properly.

What is the difference between declaring a variable and defining a variable?

In declaration we only mention the type of the variable and its name without initializing it. Defining means declaration + initialization. E.g. String s; is just a declaration while String s = new String (”bob”); Or String s = “bob”; are both definitions.

What type of parameter passing does Java support?

In Java the arguments (primitives and objects) are always passed by value. With objects, the object reference itself is passed by value and so both the original reference and parameter copy both refer to the same object.

Explain the Encapsulation principle.

Encapsulation is a process of binding or wrapping the data and the codes that operates on the data into a single entity. This keeps the data safe from outside interface and misuse. Objects allow procedures to be encapsulated with their data to reduce potential interference. One way to think about encapsulation is as a protective wrapper that prevents code and data from being arbitrarily accessed by other code defined outside the wrapper.

What do you understand by a variable?

Variable is a named memory location that can be easily referred in the program. The variable is used to hold the data and it can be changed during the course of the execution of the program.

What do you understand by numeric promotion?

The Numeric promotion is the conversion of a smaller numeric type to a larger numeric type, so that integral and floating-point operations may take place. In the numerical promotion process the byte, char, and short values are converted to int values. The int values are also converted to long values, if necessary. The long and float values are converted to double values, as required.

What do you understand by casting in java language? What are the types of casting?

The process of converting one data type to another is called Casting. There are two types of casting in Java; these are implicit casting and explicit casting.

What is the first argument of the String array in main method?

The String array is empty. It does not have any element. This is unlike C/C++ where the first element by default is the program name. If we do not provide any arguments on the command line, then the String array of main method will be empty but not null.

How can one prove that the array is not null but empty?

Print array.length. It will print 0. That means it is empty. But if it would have been null then it would have thrown a NullPointerException on attempting to print array.length.

Can an application have multiple classes having main method?

Yes. While starting the application we mention the class name to be run. The JVM will look for the main method only in the class whose name you have mentioned. Hence there is not conflict amongst the multiple classes having main method.

When is static variable loaded? Is it at compile time or runtime? When exactly a static block is loaded in Java?

Static variable are loaded when classloader brings the class to the JVM. It is not necessary that an object has to be created. Static variables will be allocated memory space when they have been loaded. The code in a static block is loaded/executed only once i.e. when the class is first initialized. A class can have any number of static blocks. Static block is not member of a class, they do not have a return statement and they cannot be called directly. Cannot contain this or super. They are primarily used to initialize static fields.

Can I have multiple main methods in the same class?

We can have multiple overloaded main methods but there can be only one main method with the following signature :

public static void main(String[] args) {}

No the program fails to compile. The compiler says that the main method is already defined in the class.

Explain working of Java Virtual Machine (JVM)?

JVM is an abstract computing machine like any other real computing machine which first converts .java file into .class file by using Compiler (.class is nothing but byte code file.) and Interpreter reads byte codes.

How can I swap two variables without using a third variable?

Add two variables and assign the value into First variable. Subtract the Second value with the result Value. and assign to Second variable. Subtract the Result of First Variable With Result of Second Variable and Assign to First Variable. Example:

int a=5,b=10;a=a+b; b=a-b; a=a-b;

An other approach to the same question

You use an XOR swap.

for example:

int a = 5; int b = 10;
a = a ^ b;
b = a ^ b;
a = a ^ b;

What is data encapsulation?

Encapsulation may be used by creating ‘get’ and ’set’ methods in a class (JAVABEAN) which are used to access the fields of the object. Typically the fields are made private while the get and set methods are public. Encapsulation can be used to validate the data that is to be stored, to do calculations on data that is stored in a field or fields, or for use in introspection (often the case when using javabeans in Struts, for instance). Wrapping of data and function into a single unit is called as data encapsulation. Encapsulation is nothing but wrapping up the data and associated methods into a single unit in such a way that data can be accessed with the help of associated methods. Encapsulation provides data security. It is nothing but data hiding.

What is reflection API? How are they implemented?

Reflection is the process of introspecting the features and state of a class at runtime and dynamically manipulate at run time. This is supported using Reflection API with built-in classes like Class, Method, Fields, Constructors etc. Example: Using Java Reflection API we can get the class name, by using the getName method.

Does JVM maintain a cache by itself? Does the JVM allocate objects in heap? Is this the OS heap or the heap maintained by the JVM? Why

Yes, the JVM maintains a cache by itself. It creates the Objects on the HEAP, but references to those objects are on the STACK.

What is phantom memory?

Phantom memory is false memory. Memory that does not exist in reality.

Can a method be static and synchronized?

A static method can be synchronized. If you do so, the JVM will obtain a lock on the java.lang.
Class instance associated with the object. It is similar to saying:

synchronized(XYZ.class) {

}

What is difference between String and StringTokenizer?

A StringTokenizer is utility class used to break up string.

Example:

StringTokenizer st = new StringTokenizer(”Hello World”);

while (st.hasMoreTokens()) {

System.out.println(st.nextToken());

}

Output:

Hello

World

Thursday, 29 January 2009

10 COMMON INTERVIEW Q&A

1. Tell me about yourself:
The most often asked question in interviews. You need to have a short
statement prepared in your mind. Be careful that it does not sound
rehearsed. Limit it to work-related items unless instructed otherwise.
Talk about things you have done and jobs you have held that relate to
the position you are interviewing for. Start with the item farthest
back and work up to the present.

2. Why did you leave your last job?
Stay positive regardless of the circumstances. Never refer to a major
problem with management and never speak ill of supervisors, co-workers
or the organization. If you do, you will be the one looking bad. Keep
smiling and talk about leaving for a positive reason such as an
opportunity, a chance to do something special or other forward-looking
reasons.

3. What experience do you have in this field?
Speak about specifics that relate to the position you are applying for.
If you do not have specific experience, get as close as you can.

4. Do you consider yourself successful?
You should always answer yes and briefly explain why. A good
explanation is that you have set goals, and you have met some and are
on track to achieve the others.

5. What do co-workers say about you?
Be prepared with a quote or two from co-workers. Either a specific
statement or a paraphrase will work. Jill Clark, a co-worker at Smith
Company, always said I was the hardest workers she had ever known. It
is as powerful as Jill having said it at the interview herself.

6. What do you know about this organization?
This question is one reason to do some research on the organization
before the interview. Find out where they have been and where they are
going. What are the current issues and who are the major players?

7. What have you done to improve your knowledge in the last year?
Try to include improvement activities that relate to the job. A wide
variety of activities can be mentioned as positive self-improvement.
Have some good ones handy to mention.

8. Are you applying for other jobs?
Be honest but do not spend a lot of time in this area. Keep the focus
on this job and what you can do for this organization. Anything else is
a distraction.

9. Why do you want to work for this organization?
This may take some thought and certainly, should be based on the
research you have done on the organization. Sincerity is extremely
important here and will easily be sensed. Relate it to your long-term
career goals.

10. Do you know anyone who works for us?
Be aware of the policy on relatives working for the organization. This
can affect your answer even though they asked about friends not
relatives. Be careful to mention a friend only if they are well thought
of.

Monday, 19 January 2009

C# Interview Questions

1. What’s the implicit name of the parameter that gets passed into the class’ set method? Value, and its datatype depends on whatever variable we’re changing.
2. How do you inherit from a class in C#? Place a colon and then the name of the base class. Notice that it’s double colon in C++.
3. Does C# support multiple inheritance? No, use interfaces instead.
4. When you inherit a protected class-level variable, who is it available to? Classes in the same namespace.
5. Are private class-level variables inherited? Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.
6. Describe the accessibility modifier protected internal. It’s available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared in).
7. C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write? Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.
8. What’s the top .NET class that everything is derived from? System.Object.
9. How’s method overriding different from overloading? When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
10. What does the keyword virtual mean in the method definition? The method can be over-ridden.
11. Can you declare the override method static while the original method is non-static? No, you can’t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.
12. Can you override private virtual methods? No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.
13. Can you prevent your class from being inherited and becoming a base class for some other classes? Yes, that’s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It’s the same concept as final class in Java.
14. Can you allow class to be inherited, but prevent the method from being over-ridden? Yes, just leave the class public and make the method sealed.
15. What’s an abstract class? A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden. Essentially, it’s a blueprint for a class without any implementation.
16. When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)? When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
17. What’s an interface class? It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.
18. Why can’t you specify the accessibility modifier for methods inside the interface? They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.
19. Can you inherit multiple interfaces? Yes, why not.
20. And if they have conflicting method names? It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
21. What’s the difference between an interface and abstract class? In the interface all methods must be abstract; in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.
22. How can you overload a method? Different parameter data types, different number of parameters, different order of parameters.
23. If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor? Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
24. What’s the difference between System.String and System.StringBuilder classes? System.String is immutable; System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
25. What’s the advantage of using System.Text.StringBuilder over System.String? StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it’s being operated on, a new instance is created.
26. Can you store multiple data types in System.Array? No.
27. What’s the difference between the System.Array.CopyTo() and System.Array.Clone()? The first one performs a deep copy of the array, the second one is shallow.
28. How can you sort the elements of the array in descending order? By calling Sort() and then Reverse() methods.
29. What’s the .NET datatype that allows the retrieval of data by a unique key? HashTable.
30. What’s class SortedList underneath? A sorted HashTable.
31. Will finally block get executed if the exception had not occurred? Yes.
32. What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
33. Can multiple catch blocks be executed? No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.
34. Why is it a bad idea to throw your own exceptions? Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.
35. What’s a delegate? A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.
36. What’s a multicast delegate? It’s a delegate that points to and eventually fires off several methods.
37. How’s the DLL Hell problem solved in .NET? Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
38. What are the ways to deploy an assembly? An MSI installer, a CAB archive, and XCOPY command.
39. What’s a satellite assembly? When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
40. What namespaces are necessary to create a localized application? System.Globalization, System.Resources.
41. What’s the difference between // comments, /* */ comments and /// comments? Single-line, multi-line and XML documentation comments.
42. How do you generate documentation from the C# file commented properly with a command-line compiler? Compile it with a /doc switch.
43. What’s the difference between and XML documentation tag? Single line code example and multiple-line code example.
44. Is XML case-sensitive? Yes, so and are different elements.
45. What debugging tools come with the .NET SDK? CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.
46. What does the This window show in the debugger? It points to the object that’s pointed to by this reference. Object’s instance data is shown.
47. What does assert() do? In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
48. What’s the difference between the Debug class and Trace class? Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
49. Why are there five tracing levels in System.Diagnostics.TraceSwitcher? The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
50. Where is the output of TextWriterTraceListener redirected? To the Console or a text file depending on the parameter passed to the constructor.
51. How do you debug an ASP.NET Web application? Attach the aspnet_wp.exe process to the DbgClr debugger.
52. What are three test cases you should go through in unit testing? Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
53. Can you change the value of a variable while debugging a C# application? Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.
54. Explain the three services model (three-tier application). Presentation (UI), business (logic and underlying code) and data (from storage or other sources).
55. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET? SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.
56. What’s the role of the DataReader class in ADO.NET connections? It returns a read-only dataset from the data source when the command is executed.
57. What is the wildcard character in SQL? Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
58. Explain ACID rule of thumb for transactions. Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
59. What connections does Microsoft SQL Server support? Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).
60. Which one is trusted and which one is untrusted? Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
61. Why would you use untrusted verificaion? Web Services might use it, as well as non-Windows applications.
62. What does the parameter Initial Catalog define inside Connection String? The database name to connect to.
63. What’s the data provider name to connect to Access database? Microsoft.Access.
64. What does Dispose method do with the connection object? Deletes it from the memory.
65. What is a pre-requisite for connection pooling? Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.

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