Bài 1:
program soduong;
uses crt;
var a:integer;
begin
clrscr;
repeat
write('Nhap a: '); readln(a);
writeln('Khong hop le(phai la so duong), nhap so khac.');
until a>0;
write(a,' la so duong');
readln;
end.
Bài 2:
program soduong;
uses crt;
var a:integer;
begin
clrscr;
repeat
write('Nhap a: '); readln(a);
writeln('Khong hop le(phai la so chan), nhap so khac.');
until a mod 2=0;
write(a,' la so chan');
readln;
end.
Bài 3:
program tinhtong;
uses crt;
var n,i,s:integer;
begin
clrscr;
write('Nhap n: '); readln(n);
i:=1; S:=0;
while i<=n do
begin
S:=S+i;
i:=i+1;
end;
write('Tong cac so tu 1 den ',n,' la: ',s);
readln;
end.
Bài 4:
program tinhS;
uses crt;
var i:integer;
s:real;
begin
clrscr;
S:=0; i:=1;
while 2-S>=0.01 do
begin
S:=S+1/i;
i:=i+1;
end;
write('S= 's:0:3);
readln;
end.