Bài 1: 

uses crt;

var n,i,s:integer;

begin

clrscr;

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

s:=0;

i:=1;

while i<=n do 

  begin

s:=s+i;

inc(i);

end;

writeln('Tong cac so trong khoang tu 1 den ',n,' la: ',s);

readln;

end.

Bài 2: 

uses crt;

var n,i,s:integer;

begin

clrscr;

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

s:=0;

i:=1;

while i<=n do 

  begin

s:=s+i;

i:=i+2;

end;

writeln('Tong cac so le trong khoang tu 1 den ',n,' la: ',s);

readln;

end.

alo

Uses crt;

var s,n,i: integer;

begin clrscr;

readln(n);

for i:=1 to n do if(n mod 2<>0) then s:=s+i;

writeln(s);

readln;

end.

Bài 2: 

a: Input: 50 số từ 1 đến 50

Output: Tổng các số nguyên tố

c: Viết chương trình:

uses crt;

var i,j,t,kt:integer;

begin

clrscr;

t:=0;

for i:=2 to 50 do 

  begin

kt:=0;

for j:=2 to trunc(sqrt(i)) do 

  if i mod j=0 then kt:=1;

if kt=0 then t:=t+i;

end;

writeln(t);

readln;

end.

Program HOC24;

var i,n: integer;

S:longint;

begin

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

s:=0;

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

write('Tong la ',s);

readln

end.

#include <bits/stdc++.h>

using namespace std;

int main()

{

int n,t=0,i,dem=0;

cin>>n;

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

if (i%2==0)

{

t=t+i;

dem++;

}

cout<<fixed<<setprecision(2)<<(t*1.0)/(dem*1.0);

return 0;

}

uses crt;

var i:integer;

a:array[1..20]of string;

begin

clrscr;

for i:=1 to 20 do readln(a[i]);

for i:=1 to 20 do 

  writeln('Xin chao, ban thu ',i,' ten la: ',a[i]);

readln;

end.

Program Hoc24;

var i: byte;

begin

for i:=1 to 20 do

writeln('Chao ban thu ',i);

readln

end.

Program HOC24;

var p: longint;

i,x: integer;

Begin

write('Nhap X: '); readln(X);

p:=1;

for i:=3 to x do if i mod 2=1 then p:=p*i;

write('P = ',p);

readln

end.