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From: Preben Randhol <randhol+news@pvv.org>
Newsgroups: comp.lang.ada
Subject: Array and memory usage
Date: Sun, 9 Mar 2003 11:19:07 +0000 (UTC)
Organization: Norwegian university of science and technology
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Date: 2003-03-09T11:19:07+00:00
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I was a bit puzzeled to see that if I do:

   type Str_Array_Type is array (1 .. 1000) of String (1 .. 800);

   type User_Data is
      record
         Name     : Str_Array_Type;
         Hostname : Str_Array_Type;
      end record;

my program uses 800 bytes of memory, while if I only change the program
like this:

   type User_Data is
      record
         Name     : Str_Array_Type := (others => (others => ' '));
         Hostname : Str_Array_Type := (others => (others => ' '));
      end record;

then the program uses 2356 bytes.

I thought all the memory needed for an array would be claimed when the
program started no matter if the array was filled or not.

Is this correct or am I just being tricked by the program that measures
the memory used by my program? 

If it is correct then it doesn't matter if I define my array as (1 ..
100) or (1 .. 10_000) as long as I don't initialize the strings.
I can just add to User_Data a:

   type Used_Type is array (1 .. 1000) of Boolean;

   Used : Used_Type := (others => False);

And then I don't need to add any linked list etc... to my small server.

I use GNAT 3.14p on i386 Linux (Debian).

Thanks in advance

Prebene Randhol
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