1, For...do           
     Program chuong_trinh_tinh_tong;
User crt;
var n,i:integer; 
S:real; 
begin; 
write('nhap n = '); 
readln(n); 
s:=0; 
for i :=1 to n do S :=S + 1/i; 
writeln('tong S = ',S:5:2); 
readln 
end.
  2, While...do
program Tinh_tong;
uses crt;
var i,n: byte; s: real;
begin
 clrscr; i:=1; s:=0;
 while i<=100 do s:=s+1/i;
 write('Tong can tim :',s:2:2); readln
end.