Control Flow — IF, CASE, and Loops in ABAP
Master ABAP control flow: IF/ELSEIF/ENDIF, CASE, DO loops, WHILE loops, and LOOP AT — with Python and Java comparisons.
Control Flow — IF, CASE, and Loops
What You'll Learn
- IF/ELSEIF/ELSE/ENDIF — conditional branching
- CASE — pattern matching (like switch)
- DO — counted loops
- WHILE — conditional loops
- LOOP AT — iterating internal tables (ABAP's foreach)
- Comparison operators and logical operators
IF / ELSEIF / ELSE / ENDIF
REPORT z_control_flow.
DATA: lv_score TYPE i VALUE 85.
IF lv_score >= 90.
WRITE: / 'Grade: A'.
ELSEIF lv_score >= 80.
WRITE: / 'Grade: B'.
ELSEIF lv_score >= 70.
WRITE: / 'Grade: C'.
ELSE.
WRITE: / 'Grade: F'.
ENDIF.Expected Output
Grade: B
Coming from Python: Python uses if/elif/else: with indentation. ABAP uses IF/ELSEIF/ELSE. with explicit ENDIF. — no indentation required (but recommended for readability).
Coming from Java: Java uses if/else if/else with braces {}. ABAP replaces braces with ENDIF.
Comparison Operators
ABAP Python Java Meaning
= == == Equal
<> != != Not equal
> > > Greater than
< < < Less than
>= >= >= Greater or equal
<= <= <= Less or equal
Important: ABAP uses = for both assignment AND comparison. The context determines which it is:
lv_x = 10. " Assignment (left side of statement)
IF lv_x = 10. " Comparison (inside IF condition)Logical Operators
DATA: lv_age TYPE i VALUE 25,
lv_salary TYPE i VALUE 95000.
* AND
IF lv_age > 20 AND lv_salary > 90000.
WRITE: / 'Young and well-paid'.
ENDIF.
* OR
IF lv_age < 20 OR lv_age > 60.
WRITE: / 'Outside typical working age'.
ENDIF.
* NOT
IF NOT lv_age > 30.
WRITE: / 'Age is 30 or below'.
ENDIF.Expected Output
Young and well-paid
Age is 30 or below
IS INITIAL — Checking for Default Values
DATA: lv_name TYPE string,
lv_count TYPE i.
IF lv_name IS INITIAL. " Empty string
WRITE: / 'Name is empty'.
ENDIF.
IF lv_count IS INITIAL. " Zero
WRITE: / 'Count is zero'.
ENDIF.IS INITIAL checks if a variable has its type-specific default value (0 for numbers, empty for strings, '00000000' for dates). It's ABAP's way of checking "has this been set?"
CASE — Pattern Matching
DATA: lv_day TYPE string VALUE 'Monday'.
CASE lv_day.
WHEN 'Monday' OR 'Tuesday' OR 'Wednesday' OR 'Thursday' OR 'Friday'.
WRITE: / 'Weekday'.
WHEN 'Saturday' OR 'Sunday'.
WRITE: / 'Weekend'.
WHEN OTHERS.
WRITE: / 'Unknown day'.
ENDCASE.Expected Output
Weekday
Coming from Python: Python uses match/case (3.10+). ABAP's CASE/WHEN is closer to Java's switch/case, but without fall-through — each WHEN block is independent, no break needed.
CASE with TYPE (checking object types)
* Used in OOP — check object type
* CASE TYPE OF lo_object.
* WHEN TYPE zcl_customer.
* " Handle customer
* WHEN TYPE zcl_vendor.
* " Handle vendor
* ENDCASE.DO — Counted Loops
* Loop exactly 5 times
DO 5 TIMES.
WRITE: / |Iteration { sy-index }|.
ENDDO.Expected Output
Iteration 1
Iteration 2
Iteration 3
Iteration 4
Iteration 5
sy-index is a system variable that contains the current loop counter (1-based, not 0-based like Python's range()).
Infinite Loop with EXIT
DATA: lv_total TYPE i.
DO.
lv_total = lv_total + 1.
IF lv_total > 3.
EXIT. " Break out of the loop
ENDIF.
WRITE: / |Count: { lv_total }|.
ENDDO.
WRITE: / |Final total: { lv_total }|.Expected Output
Count: 1
Count: 2
Count: 3
Final total: 4
EXIT is ABAP's break. CONTINUE is ABAP's continue — skip to the next iteration.
WHILE — Conditional Loops
DATA: lv_counter TYPE i VALUE 1.
WHILE lv_counter <= 5.
WRITE: / |Counter: { lv_counter }|.
lv_counter = lv_counter + 1.
ENDWHILE.Expected Output
Counter: 1
Counter: 2
Counter: 3
Counter: 4
Counter: 5
Same as Python's while and Java's while — just with ENDWHILE instead of braces or indentation.
LOOP AT — Iterating Internal Tables
This is ABAP's most distinctive loop and the one you'll use most. Internal tables (covered in depth in Lesson 9) are ABAP's equivalent of Python lists or Java ArrayLists.
* Create a simple internal table
DATA: lt_names TYPE TABLE OF string.
APPEND 'Alice' TO lt_names.
APPEND 'Bob' TO lt_names.
APPEND 'Charlie' TO lt_names.
* Loop through the table
LOOP AT lt_names INTO DATA(lv_name).
WRITE: / |Name: { lv_name }, Row: { sy-tabix }|.
ENDLOOP.Expected Output
Name: Alice, Row: 1
Name: Bob, Row: 2
Name: Charlie, Row: 3
sy-tabix is the current row index (1-based) within a LOOP AT. It's the ABAP equivalent of Python's enumerate().
LOOP with WHERE condition
DATA: BEGIN OF ls_employee,
name TYPE string,
department TYPE string,
salary TYPE i,
END OF ls_employee.
DATA: lt_employees LIKE TABLE OF ls_employee.
ls_employee-name = 'Alice'. ls_employee-department = 'Engineering'. ls_employee-salary = 120000.
APPEND ls_employee TO lt_employees.
ls_employee-name = 'Bob'. ls_employee-department = 'Marketing'. ls_employee-salary = 95000.
APPEND ls_employee TO lt_employees.
ls_employee-name = 'Charlie'. ls_employee-department = 'Engineering'. ls_employee-salary = 130000.
APPEND ls_employee TO lt_employees.
* Loop only over engineers
LOOP AT lt_employees INTO ls_employee WHERE department = 'Engineering'.
WRITE: / |{ ls_employee-name } earns { ls_employee-salary }|.
ENDLOOP.Expected Output
Alice earns 120000
Charlie earns 130000
Coming from Python: This is like for emp in employees if emp.department == 'Engineering': — but the filtering happens at the loop level, not as a separate filter step.
Control Statements Summary
ABAP Python Java
────────────── ────────────── ──────────────
IF ... ENDIF if: if { }
ELSEIF elif: else if { }
CASE ... ENDCASE match/case: switch { }
DO n TIMES for i in range(n) for (i=0; i<n; i++)
WHILE ... ENDWHILE while: while { }
LOOP AT ... ENDLOOP for x in list: for (x : list)
EXIT break break
CONTINUE continue continue
CHECK (no equivalent) (no equivalent)
CHECK — ABAP's Unique Control Statement
DO 10 TIMES.
CHECK sy-index MOD 2 = 0. " Only continue if index is even
WRITE: / |Even: { sy-index }|.
ENDDO.Expected Output
Even: 2
Even: 4
Even: 6
Even: 8
Even: 10
CHECK evaluates a condition — if true, execution continues. If false, it skips to the next iteration (like CONTINUE with a built-in IF). It's compact but can be hard to read. Many teams prefer explicit IF/CONTINUE instead.
Common Mistakes
- Forgetting ENDIF, ENDDO, ENDWHILE, ENDCASE. Every block opener needs its closer. The ABAP editor's syntax check (Ctrl+F2) catches these immediately, but they're still the #1 syntax error for newcomers.
- Using
=for comparison in ambiguous contexts.IF lv_x = lv_y.is a comparison.lv_x = lv_y.outside an IF is an assignment. This is clear to ABAP developers but confuses Python developers who use==for comparison. - Forgetting that DO/WHILE loops without EXIT can run forever. Unlike Python which has no
DOloop, ABAP'sDO.withoutTIMESruns indefinitely. Always have anEXITcondition. - Using
sy-indexoutside a DO loop.sy-indexis the DO loop counter. Inside aLOOP AT, usesy-tabixinstead. Using the wrong system variable is a common source of bugs.
Key Takeaways
IF/ELSEIF/ELSE/ENDIFandCASE/WHEN/ENDCASEhandle branching.DO n TIMESfor counted loops,WHILEfor conditional loops,LOOP ATfor iterating tables.sy-index= current DO loop counter.sy-tabix= current LOOP AT row index. Both are 1-based.EXIT= break,CONTINUE= skip to next iteration,CHECK= conditional continue.IS INITIALchecks for default values — ABAP's way of checking "empty" or "unset."- Every block ends with
END*— ENDIF, ENDDO, ENDWHILE, ENDCASE, ENDLOOP.
Next Lesson
You've seen LOOP AT and internal tables briefly. In Lesson 9: Internal Tables — ABAP's Most Important Concept, we'll dive deep into the data structure that makes ABAP unique — and the one you'll use in every single program you write.