uses crt;
var s:string; n,t,c,d:longint;
begin
   clrscr;
   repeat
      write('Nhap so 3 chu so: '); readln(n);
      str(n,s);
   until length(s)=3;
   val(s,n);
   t:=n div 100;
   c:=(n div 10) mod 10;
   d:=n mod 10;
   writeln('Chu so hang tram: ',t);
   writeln('Chu so hang chuc: ',c);
   writeln('Chu so hang don vi: ',d);
   readln
end.

* Dùng xâu

uses crt;
var n:longint; s:string;
begin
clrscr;
   write('Nhap mot so co 3 chu so: ');readln(n);
   str(n,s);
   writeln('Chu so hang tram: ',s[1]);
   writeln('Chu so hang chuc: ',s[2]);
   writeln('Chu so hang don vi: ',s[3]);
readln
end.

* Như đề bài dùng div mod:

uses crt;
var n,t:longint;
begin
clrscr;
   write('Nhap mot so co 3 chu so: ');readln(n);
   t:=100;
   writeln('Chu so hang tram: ',n div 100);
   n:=n-((n div 100)*100);
   writeln('Chu so hang chuc: ',n div 10);
   n:=n-((n div 10)*10);
   writeln('Chu so hang don vi: ',n);
readln
end.