1. Initialization
2. At selection-screen
3. Start-of-selection
4. End-of-selection
5. Top-of-page
6. End-of-page
7. At line-selection
8. At user-command
9. At PF
10. Get
11. At New
12. At LAST
13. AT END
14. AT FIRST

advantages: view is used to retrieve the data very fastly from the database tables
* memory wastage is reduced
* faster than joins to retrieve the data from database tables

disadvantages:
* view is not a container,it will not hold the data
* view memory is not permanent memory

Dispatcher recieves the request from client and assigns the request to one of the work process.
Roll area: Each workprocess works in a particular memory that memory is known as Role Area, which consists of User context and session data.
ABAP- Processor :is an interpretor which can execute logic

sap memory is a global memory whereas abap memory is local memory.

For example, we have four programs in abap memory and assigned some varibles to a particular program in abap memory then those varibles can't be used by anyother program in abap memory i.e., the variables are only for that program and also local to that memory,whereas sap memory can access all the abap memory or else it can perform any kind of modifications.

OOABAP is used to develop BSP/PCUI applications and also anthing involved object oriented like BADIs, SmartForms..etc.where as ABAP is used to develop traditional programs in R/3.

Structure and table both are 2/2 matrices but there are many differences between table and structure.

1. Table can store the data physically but a structure dose not store.
2. Table can have primary key but a structure dose not have.
3. Table can have the technical attribute but a structure dose not have.

structure doesn't contain technical attributes.
structure doesn't contain primary key.
structure doesn't stores underline database level.

ALV is Application List viewer. Sap provides a set of ALV (ABAP LIST VIEWER) function modules which can be put into use to embellish the output of a report. This set of ALV functions is used to enhance the readability and functionality of any report output. Cases arise in sap when the output of a report contains columns extending more than 255 characters in length. In such cases, this set of ALV functions can help choose selected columns and arrange the different columns from a report output and also save different variants for report display. This is a very efficient tool for dynamically sorting and arranging the columns from a report output. The report output can contain up to 90 columns in the display with the wide array of display options.

ABAP/4 Query is a powerful tool to generate simple reports without any coding. ABAP/4 Query can generate the following 3 simple reports: Basic List: It is the simple reports. Statistics: Reports with statistical functions like Average, Percentages. Ranked Lists: For analytical reports. - For creating a ABAP/4 Query, programmer has to create user group and a functional group. Functional group can be created using with or without logical database table. Finally, assign user group to functional group. Finally, create a query on the functional group generated.