DATA and TYPES

It is a special strength of ABAP that you can define a great variety of data types and objects that span the spectrum from very elementary data types to very complex and dynamic types. Consequently, the subject of ABAP declarations is quite extensive.

ABAP accepts all data types defined in the SAP dictionary or in Type Pools. Types can also be defined inside the program itself. Object numeric (I for integer, F for floating point), packed decimal (P), character (C or N, where the N type is used for numeric strings that can be used in computation) or hexadecimal (X). Date fields (type D) and time fields (type T) have a "dual" nature; in an input/output context they behave like strings, but in a computational context they are numeric integers. There are no built-in functions or statements for dealing with dates and times; but, as in spreadsheets, arithmetic can be performed on a date-value to break it up. For example:

DATESENT = '20070901'.

VALIDTO = DATESENT + 60.

WRITE: 'Offer is valid until', VALIDTO DD/MM/YYYY.

In this example, a string literal representing September 1, 2007 is assigned to DATESENT. DATESENT is then used in a numeric calculation to produce another data field, VALIDTO, which is set to DATESENT plus 60 days. Finally, VALIDTO is output as a string. The optional "DD/MM/YYYY" modifier displays the date in a predefined format, here "31/10/2007". Without the modifier the date would display as "20071031".

All ABAP variables must be explicitly declared in order to be used. The convention is for all declarations to be at the top of the program, or subroutine. The declaration consists of the name, type, length (where applicable), additional modifiers (e.g. the number of implied decimals for a packed decimal field) and optionally an initial value:

* Primitive types:

DATA: COUNTER      TYPE I,

      VALIDITY     TYPE I VALUE 60,

      TAXRATE(3)   TYPE P DECIMALS 1,

      LASTNAME(20) TYPE C.

* Dictionary types:

DATA: ORIGIN       TYPE COUNTRY.

* Internal table:

DATA: T_FLIGHTS    TYPE TABLE OF FLIGHTINFO,

      T_LOOKUP     TYPE HASHED TABLE OF FLT_LOOKUP.

* Objects:

DATA: BOOKING      TYPE REF TO CL_FLT_BOOKING.

Notice the use of the colon to chain together consecutive DATA statements.

ABAP Objects

The ABAP language supports object-oriented programming, through a feature known as "ABAP Objects". This helps to simplify applications and make them more controllable.

ABAP Objects is fully compatible with the existing language, so one can use existing statements and modularization units in programs that use ABAP Objects, and can also use ABAP Objects in existing ABAP programs. Syntax checking is stronger in ABAP Objects programs, and some syntactical forms (usually older ones) of certain statements are not permitted.

ABAP statements – an overview

The first element of an ABAP statement is the ABAP keyword. This determines the category of the statement. The different statement categories are as follows:

Declarative statements

These statements define data types or declare data objects which are used by the other statements in a program or routine. The collected declarative statements in a program or routine make up its declaration part.

Examples of declarative keywords:

TYPES, DATA, TABLES