Bài 5

uses crt;
var n: integer;
function isPrime(n: integer): boolean;
var i,c: integer;
begin
if n <= 1 then isPrime := false
else
begin
c := 0;
for i:=2 to n-1 do
    if n mod i = 0 then c := c + 1;
if c <> 0 then isPrime := false else isPrime := true;
end;
end;
begin
readln(n);
while n <> 0 do
begin
if isPrime(n) = false then writeln(n, ' khong phai la so nguyen to') else writeln(n, ' la so nguyen to');
readln(n);
end;
end.

Bài 6

uses crt;
var c: char;
begin
readln(c);
while (ord(c) >= 65) and (ord(c) <= 90) do
begin
writeln(c);
readln(c);
end;
end.

Bài 7

uses crt;
var c: char;
begin
readln(c);
while true do
begin
if (ord(c) >= 65) and (ord(c) <= 90) then writeln(c,' ',char(ord(c)+32))
else if (ord(c) >= 97) and (ord(c) <= 122) then writeln(c,' ',char(ord(c)-32))
else if (ord(c) >= 48) and (ord(c) <= 57) then writeln(c)
else break;
readln(c);
end;
end.

5.

uses crt;
var n,d,i: integer;
begin
clrscr;
    readln(n);
    while n<>0 do begin
        d:=0;
        for i:=1 to n do if n mod i = 0 then d:=d+1;
        if (d=2) then writeln('YES') else writeln('NO');
        readln(n);
    end;
readln
end.

6.

uses crt;
var a: char;
begin
clrscr;
    readln(a);
    while (ord(a)>=65) and (ord(a)<=90) do begin
        writeln(a);
        readln(a);
    end;
    readln
end.

7.

uses crt;
var a: char;
begin
clrscr;
    readln(a);
    while ((ord(a)>=0) and (ord(a)<=57)) or ((ord(a)>=54) and (ord(a)<=90)) or ((ord(a)>=97) and (ord(a)<=122)) do begin
        if ((ord(a)>=54) and (ord(a)<=90)) then writeln(a,' ',char(ord(a)+32));
        if ((ord(a)>=97) and (ord(a)<=122)) then writeln(a,' ',upcase(a));
        if ((ord(a)>=0) and (ord(a)<=57)) then writeln(a);
        readln(a);
    end;
readln
end.