What is the sysutils?

Hi i need some help with a programme i am writing in turbo delphi Im trying to make a hangman game and i either want the letter to appear or display the alphabet and the letter will disappear?

Uses SysUtils; Type TGuessStatusArray = Array[1..20] Of Char; TLettersGuessedArray = Array[1..26] Of Char; Var NewPhrase : String; PhraseHasBeenSet : Boolean; PhraseGuessed : Boolean; Choice : Integer; GuessStatusArray : TGuessStatusArray; LettersGuessedArray : TLettersGuessedArray; NextGuessedLetter : Char; Index : Integer; Procedure DisplayMenu; Begin Writeln('__________________________________'); Writeln; Writeln('1. SETTER - Makes new word/phrase'); Writeln; Writeln('2. USER - Next letter guess'); Writeln; Writeln('5. End'); Writeln; End; Function GetNewPhrase : String; Var PhraseOK : Boolean; ThisNewPhrase : String; Begin Repeat Write('Key in new phrase ...(letters and any Spaces) '); Readln(ThisNewPhrase); If Length(ThisNewPhrase) < 10 Then Begin PhraseOK := False; Writeln('Not enough letters ... '); { possible further validation check(s) } End Else Begin PhraseOK := True; GetNewPhrase := ThisNewPhrase; End; Until PhraseOK = True; End; Procedure SetUpGuessStatusArray(NewPhrase : String; Var GuessStatusArray : TGuessStatusArray); Var Position : Integer; Begin For Position := 1 To Length(NewPhrase) Do Begin If NewPhrase[Position] = ' ' Then GuessStatusArray[Position] := ' ' Else GuessStatusArray[Position] := '*'; End; End; Procedure DisplayCurrentStatus(PhraseLength : Byte; GuessStatusArray : TGuessStatusArray); Var Position : Integer; Begin For Position := 1 To PhraseLength Do Write(GuessStatusArray[Position]); Writeln; End; Function GetNextLetterGuess : Char; Var Position : Integer; GuessedLetter : Char; Begin Writeln; Write('Next guess ? '); Readln(GuessedLetter); GetNextLetterGuess := GuessedLetter; End; Function AllLettersGuessedCorrectly(GuessStatusArray: TGuessStatusArray; NewPhrase : String) : Boolean; Var Position : Integer; MissingLetter : Boolean; Begin MissingLetter := False; Position := 1; Repeat If GuessStatusArray[Position] <> NewPhrase[Position] Then MissingLetter := True Else Position := Position+1; Until (MissingLetter = True) or (Position = Length(NewPhrase)+1); If MissingLetter = False Then AllLettersGuessedCorrectly := True Else AllLettersGuessedCorrectly := False; End; { Main program block starts here } Begin PhraseHasBeenSet := False; Repeat DisplayMenu; Write('Choice? '); Readln(Choice); If Choice = 1 Then Begin NewPhrase := GetNewPhrase; SetUpGuessStatusArray(NewPhrase, GuessStatusArray); PhraseHasBeenSet := True; End; If Choice = 2 Then Begin If PhraseHasBeenSet = True Then Begin DisplayCurrentStatus(Length(NewPhrase), GuessStatusArray); NextGuessedLetter := GetNextLetterGuess; For Index := 1 To Length(NewPhrase) Do If NextGuessedLetter = NewPhrase[Index] Then GuessStatusArray[Index] := NextGuessedLetter; DisplayCurrentStatus(Length(NewPhrase), GuessStatusArray); PhraseGuessed := AllLettersGuessedCorrectly(GuessStatusArray,NewPhrase); If PhraseGuessed = True Then Writeln('You have guessed correctly'); End Else Writeln('The setter has not specified the word/phrase ..'); End; If (Choice = 5) And (PhraseGuessed = False) Then Begin Writeln('You have not completed this word/phrase...Press return to exit'); Readln; End; Until Choice = 5; End.