What happens in a procedure? And why is the minimum 256?

Question

Pascal

procedure MasToStr(var a: mas; var res: string);//формирование результирующей строки по массиву
var
   min: integer;
   k: string; c: char;
begin
   res := '';
   min := 256;
   for c := 'A' to 'Z' do
      if (a[c] > 0)  and (a[c] < min) then begin //если буква встретилась
         min := a[c];
         k := c;
      end;
   if (min < 256) then 
      res := ('Буква ' + k + ' встретилась ' + min + ' раз.')
end;

Answer 1

It is better to insert the code as code - it is more convenient to read.
An array is passed to the procedure. Where, according to the indices corresponding to the character codes, there is a certain number. Judging by the context, the previously counted number of these characters. We find the symbol with the minimum number of occurrences and form an output string with a message about it.
Since the array seems to be characters, then the initial min is chosen so that any value in it is less than it.