When declare a Array variable with character, The compiler add 3 character, see the next code :

var
   antes:char;
   m     : array [0..3] of char;
   despues : char;
begin
    antes:='a';
    m:='hola';
    despues:='z';
    Writeln('m[-4] : ',m[-4]);     // variable antes
    Writeln('m[-3] : ',m[-3]);     // 1 byte
    Writeln('m[-2] : ',m[-2]);     // 1 byte
    Writeln('m[-1] : ',m[-1]);     // 1 byte
    Writeln('m[0] : ',m[0]);        //h
    Writeln('m[1] : ',m[1]);        //o
    Writeln('m[2] : ',m[2]);       //l
    Writeln('m[3] : ',m[3]);       //a
    Writeln('m[4] : ',m[4]);       //z variable despues
    Writeln('Tamanio de m : ',Sizeof(m));
    Write('Presione Enter ... ');
    Readln()
end;

Att.
Luis Del Aguila

When declare a Array variable with character, The compiler add 3 character, see the next code :

Turn on range checking and you will get a range check error. What you get is completely normal; the code accesses the variables 'before' m[0]; If range checking is off, this is allowed.

Michael.

At 02/16/2001 06:30, you wrote:

Dear Luis,

If you declare a variable with indexes between [m..n], this means that you are allowed only to use those indexes when you use the array. In your case, m[0], m[1], m[2] and m[3] are the only allowed expressions (or, of course, an m[i] where i has a value of 0, 1, 2 or 3). The compiler notifies you with the warning 'Range check error while evaluating constants'. Actually, this should be labeled an error, not a warning, but its text clearly says: error.

Variables are completely independent. If you declare your antes, then m, then despues, you can make no assumptions about where they will be in the memory. It is far from certain that antes will be before m, even less certain that it will be immediately before it. The compiler is at perfect liberty to place these variables in any way it sees fit and for reasons of performance, they are usually aligned on multiple byte boundaries, meaning that up to a couple of bytes of hole can be between any two variables. This is the reason why you see three additional bytes between antes and m, the default alignment is at 4-byte boundaries.

If for any reason you want to keep some variables together, knowing their exact sequence, location and size, you have to use the device the language offers for this purpose, namely, a record (specifying the alignment as necessary).

Regards,

   Gabor DEAK JAHN

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