This event is used to assign values to the parameters on 
the selection screen.

The initialization event is used to execute a processing 
block before the selection screen is processed. 
Initializing parameters or program variables is done 
using 'default' or 'value' kwywords respectively. The main 
purpose of using initialization event is when we want to 
process the default values assigned to the variables and 
then make the selection screen appear according to that 
processed logic.

initialiazation event is the first event trigger in 
reports,to get the default values to the selection screen 
we  r using this event,it will trigger before the selection 
screen

it is the first event triggered by the abap runtime.
we can change the characteristics of the select option 
table.
select option table habe four fields.they are
sign 
option
low
high.
if the report is time depandent we need to initialize time 
in this event to get accurate results.
to define new data objects .

the iniliazation event is used to fill the default the
values into the selection screen before the display the
screen  program for first time in  the execute it. this
event is used to fill the default values into the selection
screen. whenever   u execute the program these values are
displayed on the screen

Initialization is the event which is triggered before 
displaying the selection-screen, using this we can 
initialize the default values to selection-screen 
parameters/select options and also for other variables 
which we are using in the program