Strings and high memory usage - delphi

Question

When I run this code in XE4, the application ends up using ~800 MB.
Why not closer to 100 MB ?
Using Ansistring instead of string makes no difference.
const
N = 10000000; // 10 million
M = 10;
var
i,j: integer;
s: string;
X: array of string;
begin
setlength(X,N);
for i:= 1 to N do
begin
s:= '';
for j:= 1 to M do s:= s+chr(65+random(25));
X[i-1]:= s;
end;
showmessage('pause');
end;

Answer 1

A string of length 10 in XE4 uses 34 Bytes of memory (see DocWiki). 20 Bytes for the content, 2 Bytes for the #0 terminator and 12 bytes management data.
Each array entry is a pointer to that kind of memory. Thus those 10 million strings in the array end up using 380 MB (340 for the strings and 40 for the array items) of memory at minimum.

Answer 2

Try this
const MaxString = 15; // you said so
type stringholder = record
strict private
var Cell: string[ MaxString * SizeOf(Char) div SizeOf(AnsiChar) ];
function GetUS: String; // in xe 4 that is a shortcut to UnicodeString actual type
procedure SetUS(const US: string);
public
property Value: string read GetUS write SetUS;
class operator Implicit(const from: string): stringholder; inline;
class operator Implicit(const from: stringholder): string; inline;
end;
function stringholder.GetUS: String;
var i: integer;
begin
i := Ord( Cell[0] );
SetLength( Result, i div (SizeOf(Char) div SizeOf(AnsiChar)) );
if i > 0 then
Move( Cell[1], Result[1], i);
end;
procedure SetUS(const US: string);
var i: integer;
begin
If US = '' then begin
Cell := ''; // constant here, not US itself
Exit;
End;
i := Length(US);
If i > MaxString then raise EInvalidCast.Create('.....'+US);
i := i * SizeOf(Char) div SizeOf(AnsiChar)
Move( US[1], Cell[1], i );
Cell(. 0 .) := AnsiChar(i);
end;
class operator stringholder.Implicit(const from: string): stringholder;
begin
Result.Value := from;
end;
class operator stringholder.Implicit(const from: stringholder): string;
begin
Result := from.Value;
end;
const
N = 10000000; // 10 million
M = 10;
var
i,j: integer;
s: string;
X: array of stringholder;
begin
setlength(X,N);
for i:= 1 to N do
begin
s:= '';
for j:= 1 to M do s:= s+chr(65+random(25));
X(. i-1 .) := s;
end;
showmessage('pause');
end;