From: jrs@merlyn.demon.co.uk   
      
   JRS:  In article <1144937299.399996.222810@e56g2000cwe.googlegroups.com>   
   , dated Thu, 13 Apr 2006 07:08:19 remote, seen in   
   news:comp.lang.pascal.borland, dik  posted :   
   >since i see it here, i have never understood the advantage of or the   
   >reason for:   
   >   
   >   function SL(const S : string ; const L : byte) : string ;   
   >   
   >vs:   
   >   
   >   function SL(S : string ; L : byte) : string ;   
      
   With "const" the compiler will allow no code that may change the values   
   of the parameters, and the same storage is used internally & externally.   
      
   With "var" instead of "const", the same storage is used internally &   
   externally, so the external value can be changed.   
      
   With neither (for which there *should* be a reserved word), the internal   
   variable is a changeable copy of the external, which is safely   
   unchanged.   
      
   Optimisation may change those, but must preserve their appearance.   
      
      
      
   Defining   procedure X(var A : integer ; const B : integer) ;   
   and calling as   X(C, C) ;   means that if X changes A, B will change.   
      
      
   See in   .   
      
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