Написать программу <<Конвертер>>

uses crt;
var
n,x:integer;
 
FUNCTION DEC2BIN(DEC: LONGINT): STRING; {в 2-ую сс}
 
VAR
  BIN : STRING;
  I, J: LONGINT;
 
BEGIN
  IF DEC = 0 THEN BIN := '0'
  ELSE
  BEGIN
    BIN := '';
    I := 0;
    WHILE (1 SHL (I + 1)) <=DEC DO I := I + 1;
    { (1 SHL (I + 1)) = 2^(I + 1) }
    FOR J := 0 TO I DO
    BEGIN
      IF (DEC SHR (I - J)) = 1 THEN BIN := BIN + '1'
      { (DEC SHR (I - J)) = DEC DIV 2^(I - J) }
      ELSE BIN := BIN + '0';
      DEC := DEC AND ((1 SHL (I - J)) - 1);
      { DEC AND ((1 SHL (I - J)) - 1) = DEC MOD 2^(I - J) }
    END;
  END;
  DEC2BIN := BIN;
END;
 
FUNCTION DEC2HEX(DEC: LONGINT): STRING; {в 16-ую сс}
 
CONST
  HEXDigts: STRING[16] = '0123456789ABCDEF';
 
VAR
  HEX : STRING;
  I, J: LONGINT;
 
BEGIN
  IF DEC = 0 THEN HEX := '0'
  ELSE
  BEGIN
    HEX := '';
    I := 0;
    WHILE (1 SHL ((I + 1) * 4)) <=DEC DO I := I + 1;
    { 16^N = 2^(N * 4) }
    { (1 SHL ((I + 1) * 4)) = 16^(I + 1) }
    FOR J := 0 TO I DO
    BEGIN
      HEX := HEX + HEXDigts[(DEC SHR ((I - J) * 4)) + 1];
      { (DEC SHR ((I - J) * 4)) = DEC DIV 16^(I - J) }
      DEC := DEC AND ((1 SHL ((I - J) * 4)) - 1);
      { DEC AND ((1 SHL ((I - J) * 4)) - 1) = DEC MOD 16^(I - J) }
    END;
  END;
  DEC2HEX := HEX;
END;
 
FUNCTION DEC2OCT(DEC: LONGINT): STRING; {в 8-ую сс}
 
CONST
  OCTDigts: STRING[8] = '01234567';
 
VAR
  OCT : STRING;
  I, J: LONGINT;
 
BEGIN
  IF DEC = 0 THEN OCT := '0'
  ELSE
  BEGIN
    OCT := '';
    I := 0;
    WHILE (1 SHL ((I + 1) * 3)) <=DEC DO I := I + 1;
    { 8^N = 2^(N * 3) }
    { (1 SHL (I + 1)) = 8^(I + 1) }
    FOR J := 0 TO I DO
    BEGIN
      OCT := OCT + OCTDigts[(DEC SHR ((I - J) * 3)) + 1];
      { (DEC SHR ((I - J) * 3)) = DEC DIV 8^(I - J) }
      DEC := DEC AND ((1 SHL ((I - J) * 3)) - 1);
      { DEC AND ((1 SHL ((I - J) * 3)) - 1) = DEC MOD 8^(I - J) }
    END;
  END;
  DEC2OCT := OCT;
END;
 
begin
clrscr;
    repeat
       write('Viberite cifru 1-2-naya, 2-8-naya, 3-16-naya: ');
    readln(n);
       until (n=1) or (n=2) or (n=3);
               writeln('Vvedite 4islo: ');
       readln(x);
case n of
1: writeln(dec2bin(x));
2: writeln(dec2oct(x));
3: writeln(dec2hex(x));
end;
readkey;
END.

begin
clrscr;
writeln('Vvedite 4islo: ');
readln(x);
writeln('2-naya: ', dec2bin(x), ' 8-naya: ', dec2oct(x), ' 16-naya: ', dec2hex(x));
readkey;
END.