ABAP is abbreviated as Advanced Business Application programming and is a programming language developed by SAP. ABAP is a 4th generation language used for developing and managing SAP application programs that include Reports, Interfaces, Forms, Module pools, Data conversions, user exits, workflows, and BADIs.

ABAP is a default programming language for all languages of SAP and was introduced with the base of JAVA.

ABAP is an important component of SAP technology. ABAP is a high-level programming language that is used for developing business applications. This language is used for creating programs for the client-server R/3 system. ABAP is a default programming language for all languages of SAP and was introduced with the base of JAVA.

SAP R/3 is a client-server architecture. In R/3, R stands for Real-time, and three stands for 3-tier architecture. SAP R/3 refers to systems application and processing structure for real-time data processing. SAP R/3 has a 3-tier architecture, i.e., Presentation layer, Application layer, and Database layer.

• Presentation or External Layer
• Application or ABAP/4 Layer
• Database Layer

SAP R/3 has a 3-tier architecture, i.e., Presentation layer, Application layer, and Database layer.

The Presentation layer is an interface between the R/3 system and its end-users. This layer is distributed to clients, customers, or individual users' workstations. It receives the data from the input devices and sends it to the application layer (server) to process the data. Moreover, it is also responsible for receiving the processed data from the application layer and sending the same to the devices where the result is required to display.

The Application layer is an intermediate layer responsible for processing the inputs from the presentation layer. The application layer is implemented using application servers. Application server(s) can be one or multiple. Each Application server can contain either one or multiple services to run an R/3 system. It communicates to the database layer with input from the presentation layer, processes input, and sends the results back to the presentation layer. The application layer contains the ABAP runtime environment where the ABAP programs are executed.

The Database layer contains the central database system of all the data in the R/3 system. This database layer installs on different servers due to security, performance, and processing issues. This layer is responsible for processing the application layer's requests and sending back the required information. In general, SQL or ORACLE servers are used in the database layer.

ABAP/4 layer specifies the data formats used by the ABAP/4 processor.

The components are -

• Work Processes
• Dispatcher
• Gateway
• Shared Memory

Database layer contains the central database system of all the data in the R/3 system. This database layer installs on different servers due to security, performance, and processing issues. This layer is responsible for processing the application layer's requests and sending back the required information. In general, SQL or ORACLE servers are used in the database layer.

An Application server manages the output/input of ABAP/4 programs and interprets them. Application servers are groups of executables.

Presentation servers are user programs from the workstations named - Sapgui.exe.

We should use these modules - UPLOAD or WS_UPLOAD for the presentation server and OPEN DATASET, CLOSE DATASET, READ DATASET for the application server.

To read files from Application server, we need to use the commands -

• OPEN DATASET - Opens the file(dataset) either in read /write mode.
• READ DATASET - Read the file.
• CLOSE DATASET - Close the dataset once the date has been read.

We need to use the below Function Modules to read/write -

• GUI_UPLOAD - To read data from the file into an internal table.
• GUI_DOWNLOAD - To write data from an internal table to a file on the presentation server.

• SAP memory is a global memory.
• ABAP memory is local memory.

SAP dispatcher is a control agent that manages resources for the R/3 applications.

There are two editors available in ABAP, and those are - SE38 and SE80.

• In SE38, we can create programs, view online reports, and perform all the objects developments.
• In SE80, there are additional features such as creating packages, function groups, module pools, classes, programs, and BSP applications apart from the above.

We can create programs, view online reports, and perform all the objects developments, packages, function groups, module pools, classes, programs, and BSP applications using editors.

There are maximum 6 sessions open in SAPgui.