ABAP ALPHA conversion

*&---------------------------------------------------------------------*
*& Report Z_CONVERT_NUM_STRING
*&
*&---------------------------------------------------------------------*
*&
*&
*&---------------------------------------------------------------------*

REPORT z_convert_num_string.

DATA: input TYPE n LENGTH 5,
output TYPE string.

input = 123.

*-----------------------------------------------------------------------------*
*Short Text
*Conversion exit ALPHA, external->internal
*
*ALPHA conversion is used especially with account numbers.
*During conversion from the external to the internal format,
*the system checks to see if input in the INPUT field is purely numeric,
*that is, if this input consists only of numbers,
*possibly with spaces before and after them. If this is the case,
*then the number string is inserted right-justified in the display field OUTPUT
*and all spaces to the left of the value are filled with zeroes ('0').
*If the input is not purely numeric, it is inserted in the display field from left to right
*and all extra spaces are filled with blanks.
*
*Example:
*
*(Input field and output field are both eight characters in length)
*
*1. '1234 ' --> '00001234'
*2. 'ABCD ' --> 'ABCD '
*3. ' 1234 ' --> '00001234'
*
*Conversion from the internal to the external format
*(function module CONVERSION_EXIT_ALPHA_OUTPUT) is undertaken in exactly the opposite manner.
*-------------------------------------------------------------------------------*

CALL FUNCTION 'CONVERSION_EXIT_ALPHA_INPUT'
EXPORTING
input = input
IMPORTING
output = output.

WRITE: / 'From external to internal format:', output.

CLEAR: INPUT, OUTPUT.
INPUT = 00024.

CALL FUNCTION 'CONVERSION_EXIT_ALPHA_OUTPUT'
EXPORTING
input = input
IMPORTING
output = output.

WRITE: / 'From internal to external format:', output.