ABAP Control Structures

Control structures in ABAP allow for conditional execution and looping, enabling the creation of complex logic within programs. This guide provides an in-depth overview of the control structures available in ABAP, including conditional statements, loops, and case structures.

Conditional Statements

IF...ENDIF

• Basic Syntax:

  IF condition.
      " code to execute if condition is true
  ENDIF.
  

• With ELSE:

  IF condition.
      " code to execute if condition is true
  ELSE.
      " code to execute if condition is false
  ENDIF.
  

• With ELSEIF:

  IF condition1.
      " code to execute if condition1 is true
  ELSEIF condition2.
      " code to execute if condition2 is true
  ELSE.
      " code to execute if both conditions are false
  ENDIF.
  

• Nested IF Statements:

  IF condition1.
      IF condition2.
          " code to execute if both conditions are true
      ENDIF.
  ENDIF.
  

CASE...ENDCASE

• Basic Syntax:

  CASE variable.
      WHEN value1.
          " code to execute if variable equals value1
      WHEN value2.
          " code to execute if variable equals value2
      WHEN OTHERS.
          " code to execute if variable does not match any previous value
  ENDCASE.
  

• Example:

  DATA: lv_color TYPE char10.
  
  CASE lv_color.
      WHEN 'RED'.
          WRITE: / 'Stop'.
      WHEN 'GREEN'.
          WRITE: / 'Go'.
      WHEN 'YELLOW'.
          WRITE: / 'Caution'.
      WHEN OTHERS.
          WRITE: / 'Invalid color'.
  ENDCASE.
  

Looping Structures

DO...ENDDO

• Fixed-Number Loop:

  DO 5 TIMES.
      " code to execute 5 times
  ENDDO.
  

• Infinite Loop (with EXIT):

  DO.
      " code to execute indefinitely
      IF condition.
          EXIT.
      ENDIF.
  ENDDO.
  

WHILE...ENDWHILE

• Basic Syntax:

  WHILE condition.
      " code to execute while condition is true
  ENDWHILE.
  

• Example:

  DATA: lv_count TYPE I VALUE 1.
  
  WHILE lv_count <= 10.
      WRITE: / lv_count.
      lv_count = lv_count + 1.
  ENDWHILE.
  

LOOP AT...ENDLOOP

• Looping Through Internal Tables:

  LOOP AT it_table INTO wa_table.
      " code to execute for each row in the internal table
  ENDLOOP.
  

• Example:

  DATA: it_students TYPE TABLE OF string,
        wa_student  TYPE string.
  
  LOOP AT it_students INTO wa_student.
      WRITE: / wa_student.
  ENDLOOP.
  

Other Control Flow Commands

CHECK

• Usage:

  CHECK condition.
  

  • If the condition is false, the current iteration of a loop or processing block is terminated, and control passes to the next iteration or the next statement after the loop.

• Example:

  DATA: lv_num TYPE I.
  
  DO 10 TIMES.
      lv_num = lv_num + 1.
      CHECK lv_num MOD 2 = 0.
      WRITE: / lv_num.
  ENDDO.
  

EXIT

• Usage:

  EXIT.
  

  • Exits the current loop or processing block immediately.

• Example:

  DO 10 TIMES.
      IF lv_num = 5.
          EXIT.
      ENDIF.
      WRITE: / lv_num.
  ENDDO.
  

CONTINUE

• Usage:

  CONTINUE.
  

  • Skips the remaining statements in the current loop iteration and proceeds with the next iteration.

• Example:

  DO 10 TIMES.
      lv_num = lv_num + 1.
      IF lv_num MOD 2 <> 0.
          CONTINUE.
      ENDIF.
      WRITE: / lv_num.
  ENDDO.
  

RETURN

• Usage:

  RETURN.
  

  • Exits the current subroutine, function module, or method.

• Example:

  FORM example_form.
      IF condition = 'exit'.
          RETURN.
      ENDIF.
      WRITE: / 'Condition not met'.
  ENDFORM.
  

Example Program with Control Structures

REPORT z_control_structures_example.

DATA: lv_num TYPE I VALUE 1,
      lv_sum TYPE I VALUE 0.

WHILE lv_num <= 10.
    IF lv_num MOD 2 = 0.
        WRITE: / 'Even number:', lv_num.
    ELSE.
        WRITE: / 'Odd number:', lv_num.
    ENDIF.

    lv_sum = lv_sum + lv_num.

    IF lv_sum > 20.
        EXIT.
    ENDIF.

    lv_num = lv_num + 1.
ENDWHILE.

WRITE: / 'Sum:', lv_sum.

Conclusion

This guide provides a comprehensive overview of the control structures in ABAP, which are essential for creating logical and efficient programs. These structures allow for the manipulation of program flow, enabling complex decision-making and iteration over data sets. For more advanced usage and specific scenarios, consult the SAP documentation or additional resources.