{********************************************************************
 * Task 18 Telephone Directory (Bubble Sort)                        *
 * Date written : 4 May 2006                                        *
 * Author       : CW Chan                                           *
 ********************************************************************}
 
program t18;
const cls_size = 45;
var       class : string[2];
      classfile : text;
    name, phone : array[1..cls_size] of string;
              i : integer;
    sorted : boolean;
    pass, nstudent : integer;

procedure swap (var first, second : string);
var temp : string;
begin {swap}
   temp   := first;
   first  := second;
   second := temp;
end; {swap}


begin {main}
   write('Class : ');
   readln(class);
   assign(classfile, class + 'phone.dat');
   reset(classfile);
   i := 0;
   while not eof(classfile) do
      begin
         i := i + 1;
         readln(classfile, name[i]);
         readln(classfile, phone[i]);
      end;
   nstudent := i;
   close(classfile);

   sorted := false;
   pass := 1;
   while (pass < nstudent) and (not sorted) do
      begin
         sorted := true;
         for i := 1 to (nstudent - Pass) do
            if name[i] > name[i+1] then
               begin
                  sorted := false;
                  swap(name[i], name[i+1]);
                  swap(phone[i], phone[i+1]);
               end;
         pass := pass + 1 ;
      end; 
   writeln;
   writeln('Telephone Directory in alphabetic order');
   writeln('=======================================');
   writeln;     
   assign(classfile, class + 'phone.dat');
   rewrite(classfile);
   for i := 1 to nstudent do
      begin
         writeln(classfile, name[i]);
         writeln(classfile, phone[i]);
         writeln('    ', name[i], ' ':20-length(name[i]) , phone[i]);
      end;
   close(classfile);   
end. {main}