Author: Tomas Rutkauskas 

How to calculate the size of a record

Answer:

Here's some code where StrucGrid is a StringGrid holding the table structure in 
DBD-like single char indentifiers in Col1 and, if applicable, field size in Col2. 
SpinEdit2 holds the blocksize in byte.
1   
2   procedure TMainFrm.CalculateRecordSizeClick(Sender: TObject);
3   var
4     MaxRecs, RecSize, RecsPerBlock, FreeSpace: Longint;
5     i: Integer;
6   begin
7     RecSize := 0;
8     with StrucGrid do
9     begin
10      for i := 0 to pred(RowCount) do
11      begin
12        case Cells[1, i][1] of
13          'A': RecSize := RecSize + StrToInt(Cells[2, i]);
14          'D', 'T', 'I', '+': RecSize := RecSize + 4;
15          'N', '$', 'Y', '@': RecSize := RecSize + 8;
16          'M', 'B', 'F', 'O', 'G': RecSize := RecSize + 10 + StrToInt(Cells[2, i]);
17          'S': RecSize := RecSize + 2;
18          'L': RecSize := RecSize + 1;
19        end;
20      end;
21    end;
22    RecsPerBlock := (SpinEdit2.Value - 6) div RecSize;
23    FreeSpace := (SpinEdit2.Value - 6) - (RecSize * RecsPerBlock);
24    MaxRecs := 65536 * RecsPerBlock;
25    ShowMessage('Record Size is: ' + IntToStr(RecSize) + ' bytes' + #13#10
26      + 'Records per Block: ' + IntToStr(RecsPerBlock) + #13#10
27      + 'Unused Space per Block: ' + IntToStr(FreeSpace) + ' bytes' + #13#10
28      + 'Max No of Records in Table: ' + FormatFloat('###############,', MaxRecs));
29  end;