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02 — Data Types

📖 Introduction

ABAP is a strongly typed language. Before you can store a value, you must declare its type — either an elementary type (c, n, i, p, string, ...) or a structured type (TYPES ... BEGIN OF). This chapter covers structures and common string-cleanup functions used together with data declarations.

🧱 Elementary Data Types Cheat Sheet

Type Description Example
c Fixed-length character DATA lv_char TYPE c LENGTH 10.
n Numeric text (digits only, leading zeros) DATA lv_num TYPE n LENGTH 4.
i / int4 Integer DATA lv_int TYPE i.
p Packed decimal DATA lv_amt TYPE p LENGTH 8 DECIMALS 2.
string Variable-length character string DATA lv_str TYPE string.
d / datum Date (YYYYMMDD) DATA lv_date TYPE d.
t / tims Time (HHMMSS) DATA lv_time TYPE t.
xstring Variable-length byte string (binary) DATA lv_bin TYPE xstring.

🧩 Structures

A structure groups related fields together, similar to a struct in C or a record in other languages.

TYPES: BEGIN OF ty_viqmel,
         notif_no    TYPE char10,
         notif_type  TYPE char2,
         description TYPE char40,
       END OF ty_viqmel.

DATA ls_viqmel TYPE ty_viqmel.

See 07-Internal-Tables for building tables of structures, and 08-Open-SQL for reading DB tables directly into structures.

🧹 Cleaning Up String Data

Two very common statements when working with character data read from the database or user input:

" Condense: Delete Space
CONDENSE lv_data.

" Shift: Delete Beginning Zeros
SHIFT lv_data LEFT DELETING LEADING '0'.
Statement Purpose
CONDENSE Removes leading blanks and collapses each run of internal blanks to a single blank. With NO-GAPS, removes all blanks
SHIFT ... LEFT DELETING LEADING '0' Strips leading zeros — useful before comparing numeric-looking strings

🔁 Type Conversions

ABAP performs a lot of implicit conversions, but it's important to know how to convert explicitly, especially between internal keys and their "human readable" (ALPHA) form.

" ALPHA IN: Add leading zeros (internal format)
DATA lv_vbeln TYPE char10.
lv_vbeln = |{ is_data-vbeln ALPHA = IN }|.

" ALPHA OUT: Remove leading zeros (external/display format)
lv_vbeln = |{ is_data-vbeln ALPHA = OUT }|.

" Explicit type conversion with CONV
DATA(lv_data)  = CONV int4( ls_data-value ).
DATA(ls_data)  = CORRESPONDING zsm_t_data( ls_xdata ).

Conversion exits (CONVERSION_EXIT_*) are the classical, function-module–based way of doing the same thing and are still widely used with material numbers, dates, and other domain-specific fields — see 09-Modularization.

✅ Best Practices

  • Prefer string for text of unknown/variable length; use fixed c/n types only when the length is business-defined (e.g., document number).
  • Use CORRESPONDING #( ) instead of field-by-field MOVE statements when converting between similar structures.
  • Always double check decimal places (DECIMALS) for p type fields dealing with currency/quantity to avoid rounding bugs.

⚠️ Common Mistakes

  • Comparing an ALPHA-converted key (with leading zeros) to a raw user-input value without converting both sides consistently.
  • Using c type for numbers that need arithmetic — use n only for numeric-looking IDs, never for calculations.
  • Forgetting CONDENSE before string comparisons/concatenations, leading to subtle whitespace bugs.

🎤 Interview Tips

  • Be able to explain the difference between c, n, string, and when to use each.
  • Know what CORRESPONDING #( ) does and how it differs from MOVE-CORRESPONDING.
  • Explain what the ALPHA conversion exit does and why it matters for SAP key fields (e.g., material number, document number).

🔗 Related Chapters