Is it possible to get Format() to pad with leading zeros rather than spaces, particularly in the case of hex numbers? My understanding is that printf() interprets e.g. %02s as being padded with zeros.

In a similar vein, am I correct in understanding that FPC's Format() doesn't allow the case to be controlled in hex output? C's printf() distinguishes between %x and %X for case control.

Mark Morgan Lloyd wrote

Is it possible to get Format() to pad with leading zeros rather than spaces, particularly in the case of hex numbers? My understanding is that printf() interprets e.g. %02s as being padded with zeros.

For string arguments, this is not possible.
You can use %.2d for this, or %.2x for hex numbers:

araminta: >./tf
000F
araminta: >cat tf.pp
uses sysutils;

begin
   writeln(format('%.4x',[15]));
end.

In a similar vein, am I correct in understanding that FPC's Format() doesn't allow the case to be controlled in hex output? C's printf() distinguishes between %x and %X for case control.

You are correct in your understanding.

Michael.

My mistake, I meant %02x.

Thanks, I now see that is described in the example at http://lazarus-ccr.sourceforge.net/docs/rtl/sysutils/format.html but not in the preceding formal documentation.

Reminder noted with thanks.