Q:

Format('%7.8f', [varFloat]) formatting only decimals

Format('%7.8f', [varFloat]) formatting only decimals.
For example 13,98 becomes 13,98000000.
What I have to use is :
00000013,98000000
I know it is a dull question, but I am running short of time and I can not find why is not working as I would like.

A:

If you are prepared to reach into the system C runtime you can use sprintf. For example:
{$APPTYPE CONSOLE}

function sprintf(buf: Pointer; format: PAnsiChar): Integer; cdecl; 
  varargs; external 'msvcrt.dll';

var
  buf: array [0..255] of AnsiChar;
  val: Double;

begin
  val := 13.98;
  sprintf(@buf, '%015.8f', val);
  Writeln(buf);
  Readln;
end.

This outputs:

000013.98000000

You might contemplate choosing a variant that protects against buffer overruns.
But FormatFloat would be easier.

