Variable length string

["Shitij" <shitij.sah@sisl.co.in>]

Hi,
Iam new to ADA.I just wanted to know how do you define a variable length
string.I have declared a string array of length say a size of 20.But if I
use get and pass this string as an arguement,then unless and until I fill
this with exactly 20 characters my program is not working.How to overcome
this?
Iam using the below structure

type list;
 type pList is access list;
 type list is
record
   data:integer;
   str:string(1 .. 20);
   next:pList:=NULL;
  end record;