In Chapter 3, you ran your first ABAP program. It printed a fixed greeting. That was a milestone, but the greeting was hard-coded — the program always said the same thing, no matter what.

Real ABAP programs are not like that. They read data from databases, receive input from users, calculate values, and respond dynamically. To do any of that, you need to understand variables — named containers that hold changeable values — and the data types that define what kind of value they can hold.

This chapter also covers one of the most underrated topics in ABAP: system fields. These are built-in variables that SAP updates automatically after every important operation, and they are how your programs know whether something succeeded or failed. Every interview tests system fields. This chapter teaches them properly.

🎯 What You Will Learn in This Chapter

• The core ABAP data types and when to use each one
• How to declare variables with DATA and assign values
• How to declare constants with CONSTANTS so values cannot be changed
• How to group related variables into a structure
• The most important system fields and what they tell you
• How sy-subrc and sy-tabix power real ABAP logic
• How to check system fields to handle errors gracefully

🧭 Which Path Should I Choose?

Before writing code, decide which path applies to you. This chapter has two tracks running in parallel.

What You Can Do With Each Path

📘 The Core ABAP Data Types

A data type tells the system what kind of value a variable can hold, and how much space it needs. In ABAP, types are defined with single letters for primitive types, and the lengths are specified in parentheses.

Here are the ones you will use most often:

📦 Declaring and Using Variables

A variable is a named container. You declare it with the DATA statement, giving it a name and a type.

Basic Declaration

DATA lv_name   TYPE string.
DATA lv_age    TYPE i.
DATA lv_salary TYPE p DECIMALS 2.
DATA lv_city   TYPE c LENGTH 20.

Let’s decode each one:

• lv_name — a string, no fixed length
• lv_age — an integer, holds whole numbers
• lv_salary — a packed decimal with 2 decimal places
• lv_city — a character field, 20 characters wide

Assigning Values

There are three ways to put a value into a variable:

" Method 1: Direct assignment
lv_name = 'Rahul'.
lv_age  = 28.
lv_city = 'Pune'.

" Method 2: Declare and assign in one line
DATA(lv_country) = 'India'.

" Method 3: Using VALUE (modern ABAP style)
DATA(lv_status) = VALUE string( 'Active' ).

Reading Variable Values

In ABAP Cloud, you output variable values with cl_demo_output:

cl_demo_output=>write( 'Name:' && lv_name ).
cl_demo_output=>write( 'Age:'  && lv_age ).
cl_demo_output=>write( 'City:' && lv_city ).
cl_demo_output=>display( ).

The && operator concatenates strings. In the output above, the variable name is merged with the label text.

🔒 Constants — Values That Never Change

A constant is a variable whose value is fixed at declaration and cannot be changed afterwards. If you try to change it, the syntax check fails.

CONSTANTS c_pi        TYPE p DECIMALS 5 VALUE '3.14159'.
CONSTANTS c_tax_rate  TYPE p DECIMALS 2 VALUE '0.18'.
CONSTANTS c_company   TYPE string VALUE 'eLearning Solutions'.

Constants are declared with CONSTANTS instead of DATA, and they use VALUE for the initial assignment. The c_ prefix is the naming convention.

🏗️ Structures — Grouping Related Variables

A structure is a group of related variables under one name. Each field inside the structure has its own type.

TYPES: BEGIN OF ty_employee,
         name   TYPE string,
         age    TYPE i,
         salary TYPE p DECIMALS 2,
         city   TYPE c LENGTH 20,
       END OF ty_employee.

DATA ls_employee TYPE ty_employee.

Now you can fill the structure field by field:

ls_employee-name   = 'Rahul'.
ls_employee-age    = 28.
ls_employee-salary = '45000.00'.
ls_employee-city   = 'Pune'.

The hyphen (-) accesses individual fields of the structure. This is cleaner than declaring four separate variables when they logically belong together.

⚙️ System Fields — ABAP’s Built-In Variables

System fields are special variables that SAP updates automatically after every important operation. You do not declare them. You just read them. They always start with sy-.

Here are the most important ones:

The most important one: sy-subrc

sy-subrc stands for “system subreturn code”. It is ABAP’s way of telling you whether the previous operation succeeded. 0 means success. Any non-zero value means something went wrong.

Example: after a database read, you must check sy-subrc:

SELECT SINGLE * FROM zemployees
  INTO @DATA(ls_emp)
  WHERE id = @lv_id.

IF sy-subrc = 0.
  cl_demo_output=>write( 'Record found!' ).
ELSE.
  cl_demo_output=>write( 'No record found for that ID.' ).
ENDIF.

cl_demo_output=>display( ).

sy-tabix — the loop index

sy-tabix gives you the row number during internal table operations. You will use it heavily once you reach Chapter 7, but a small preview:

LOOP AT lt_employees INTO ls_emp.
  cl_demo_output=>write( 'Row' && sy-tabix && ':' && ls_emp-name ).
ENDLOOP.

sy-datum and sy-uzeit — the current date and time

These give you the system’s current date and time. Example usage:

cl_demo_output=>write( 'Today is:' && sy-datum ).
cl_demo_output=>write( 'Time is:'  && sy-uzeit ).
cl_demo_output=>write( 'User:'     && sy-uname ).

🛠 Step 1: Build a Program That Uses Variables (Both Paths)

Let’s put it all together. You will build a small program that stores employee data in variables, uses constants, groups fields into a structure, and reads system fields.

🟢 Free Path (ABAP Cloud in Eclipse ADT)

Open your ABAP Cloud project. Create a new class called ZCL_DATA_TYPES_CH4 in your package ZHELLO_WORLD.

CLASS zcl_data_types_ch4 DEFINITION
  PUBLIC
  FINAL
  CREATE PUBLIC.

  PUBLIC SECTION.
    CLASS-METHODS run.

ENDCLASS.

CLASS zcl_data_types_ch4 IMPLEMENTATION.

  METHOD run.

    " Simple variables
    DATA lv_name   TYPE string.
    DATA lv_age    TYPE i.
    DATA lv_city   TYPE string.
    DATA lv_salary TYPE p DECIMALS 2.

    " Constant
    CONSTANTS c_company TYPE string VALUE 'eLearning Solutions'.

    " Structure
    TYPES: BEGIN OF ty_employee,
             name   TYPE string,
             age    TYPE i,
             city   TYPE string,
             salary TYPE p DECIMALS 2,
           END OF ty_employee.

    DATA ls_employee TYPE ty_employee.

    " Fill the simple variables
    lv_name   = 'Rahul'.
    lv_age    = 28.
    lv_city   = 'Pune'.
    lv_salary = '45000.00'.

    " Fill the structure
    ls_employee-name   = lv_name.
    ls_employee-age    = lv_age.
    ls_employee-city   = lv_city.
    ls_employee-salary = lv_salary.

    " Output the data
    cl_demo_output=>write( '--- Employee Info ---' ).
    cl_demo_output=>write( |Name: { ls_employee-name }| ).
    cl_demo_output=>write( |Age: { ls_employee-age }| ).
    cl_demo_output=>write( |City: { ls_employee-city }| ).
    cl_demo_output=>write( |Salary: { ls_employee-salary }| ).

    " Output constants and system fields
    cl_demo_output=>write( '--- Context ---' ).
    cl_demo_output=>write( |Company: { c_company }| ).
    cl_demo_output=>write( |Today: { sy-datum }| ).
    cl_demo_output=>write( |Time: { sy-uzeit }| ).
    cl_demo_output=>write( |User: { sy-uname }| ).

    cl_demo_output=>display( ).

  ENDMETHOD.

ENDCLASS.

Save with Ctrl + S, activate with Ctrl + F3, and run with F9. You should see all the employee information, the company constant, and the system fields displayed in the console.

🔵 Paid Path (Classic ABAP in SE38)

Now open SAP GUI, go to SE38, and create a report called ZDATATYPES_CH4_REPORT with the same logic. The syntax is nearly identical — only the output method changes.

REPORT zdatatypes_ch4_report.

DATA: lv_name   TYPE string,
      lv_age    TYPE i,
      lv_city   TYPE string,
      lv_salary TYPE p DECIMALS 2.

CONSTANTS c_company TYPE string VALUE 'eLearning Solutions'.

TYPES: BEGIN OF ty_employee,
         name   TYPE string,
         age    TYPE i,
         city   TYPE string,
         salary TYPE p DECIMALS 2,
       END OF ty_employee.

DATA ls_employee TYPE ty_employee.

lv_name   = 'Rahul'.
lv_age    = 28.
lv_city   = 'Pune'.
lv_salary = '45000.00'.

ls_employee-name   = lv_name.
ls_employee-age    = lv_age.
ls_employee-city   = lv_city.
ls_employee-salary = lv_salary.

WRITE: / '--- Employee Info ---',
       / 'Name:',   ls_employee-name,
       / 'Age:',    ls_employee-age,
       / 'City:',   ls_employee-city,
       / 'Salary:', ls_employee-salary.

WRITE: / '--- Context ---',
       / 'Company:', c_company,
       / 'Today:',   sy-datum,
       / 'Time:',    sy-uzeit,
       / 'User:',    sy-uname.

Check syntax with Ctrl + F2, activate with Ctrl + F2, and run with F8.

🧮 Step 2: Add Simple Arithmetic

Variables exist to be manipulated. Let’s add a small calculation to demonstrate.

DATA lv_hours   TYPE i VALUE 160.
DATA lv_rate    TYPE p DECIMALS 2 VALUE '500.00'.
DATA lv_total   TYPE p DECIMALS 2.

lv_total = lv_hours * lv_rate.

cl_demo_output=>write( |Total monthly pay: { lv_total }| ).
cl_demo_output=>display( ).

ABAP supports the standard arithmetic operators: +, -, *, /, and the remainder operator MOD. The result of a calculation stored into a variable keeps the type of the target variable.

🧠 What Just Happened Under the Hood

Understanding how ABAP treats data at a lower level will help you avoid subtle bugs.

📝 Chapter Summary

• The core ABAP data types are I (integer), P (packed decimal), C (character), N (numeric text), D (date), T (time), and STRING.
• Variables are declared with DATA. The lv_ prefix means “local variable”.
• Constants are declared with CONSTANTS and cannot be changed. The c_ prefix means “constant”.
• Structures group related variables under one name. Use the hyphen to access fields: ls_employee-name.
• System fields start with sy- and are updated automatically by SAP.
• sy-subrc is the most important one — 0 means success, non-zero means failure. Always check it.
• sy-tabix gives you the current row index during internal table loops.
• sy-datum, sy-uzeit, and sy-uname give you the current date, time, and user.
• The syntax for variables and constants is identical in Cloud and Classic ABAP. Only the output method differs.