uses crt;

var i,n:integer;

s:real;

begin

clrscr;

write('Nhap n='); readln(n);

s:=1;

i:=1;

while i<=n do 

  begin

s:=s*i;

i:=i+1;

end;

writeln(s:0:0);

readln;

end.

Program HOC24;

var i: byte;

t: integer;

begin

t:=0;

for i:=1 to 100 do t:=t+i;

write(t);

readln

end.

program Tinh_Tong;

var n, s, i: integer;

begin
  write('Nhap vao so nguyen duong n: ');
  readln(n);
  s := 0;
  i := 1;
  while i <= n do
  begin
    s := s + i;
    i := i + 1;
  end;
  writeln('Tong cua ', n, ' so tu nhien dau tien la: ', s);
  end.

Sử dụng vòng lặp while...do:

program TinhTong20SoTNN;
var
  i, sum: integer;
begin
  i := 1;
  sum := 0;
  while i <= 20 do
  begin
    sum := sum + i;
    i := i + 1;
  end;
  writeln('Tong cua 20 so tu nhien dau tien la: ', sum);
end.

Sử dụng vòng lặp for...do:

program TinhTong20SoTNN;
var
  i, sum: integer;
begin
  sum := 0;
  for i := 1 to 20 do
    sum := sum + i;
  writeln('Tong cua 20 so tu nhien dau tien la: ', sum);
end.

uses crt;

var n,i,t:integer;

begin

clrscr;

readln(n);

t:=0;

for i:=1 to n do t:=t+i;

write(t);

readln;

end.

Program Tinh_tong ; 

Uses Crt;

Var i ,S: integer ; 

Begin

S: = 0 i;=0 ;

While  < 51 do begin 

                                       i : = i + 1 ;  

                                       S: = S + i ;

                                   end ;

 Write ('Tong la',S);

End. 

#include <bits/stdc++.h>

using namespace std;

long long n,i,t;

int main()

{

cin>>n;

t=1;

for (int i=1; i<=n; i++) t=t*i;

cout<<t;

return 0;

}