Dùng function:
uses crt;
var n:longint;
function tong(a:longint):longint;
begin
tong:=0;
repeat
inc(tong,a mod 10);
a:=a div 10;
until a=0;
end;
begin
clrscr;
write('Nhap mot so: ');readln(n);
writeln('Tong cac chu so cua so do: ',tong(n));
readln
end.
Không dùng function:
uses crt;
var n,tong:longint;
begin
clrscr;
write('Nhap mot so: ');readln(n);
tong:=0;
repeat
inc(tong,n mod 10);
n:=n div 10;
until n=0;
writeln('Tong cac chu so cua so do: ',tong);
readln
end.