Procedure errors!

Hi guys,ive written a program based on master mind using numbers 0-9 instead of colours, i have to do it in a procedure form and use paramter passing, no global variables, and records (which i havent done yet). Heres my program so far! If anyone knows why the error messages are appearing, pls let me know! thanks!

Program StudProg2;

uses SysUtils;

var
Counter: integer;
Ran1, Ran2, Ran3, Ran4: Integer;
Num1, Num2, Num3, Num4: integer;

procedure WelcomeScreen (Var Counter: integer);
Begin
writeln('********************************');
writeln('*****Welcome to Codebreaker*****');
writeln('********************************');
writeln;
writeln(' You must guess the four digit code');
writeln('The numbers in the code vary from 0-9');
writeln('X -> the number in this position is correct');
writeln('O -> the number in this position is present but not at this position');
writeln('_ -> the number in this position is not in the code');
writeln;
writeln('e.g. X O _ _ means: number 1 is correct');
writeln(' number 2 is present but not at this position');
writeln(' number 3 and number 4 are not present');
Counter := 0
End;// end of welcome module

procedure Generate_Random_Number (Ran1, Ran2, Ran3, Ran4: integer);
Begin
Randomize;
Ran1 := Random(10);
Ran2 := Random(10);
Ran3 := Random(10);
Ran4 := Random(10);
End;//End of generating random number


procedure User_Input_and_Comparing_Random_and_Guess (Counter, Ran1, Ran2, Ran3, Ran4, Num1, Num2, Num3, Num4 : Integer);
Begin
Begin // Parameters of Numbers and Messages
write('Enter Number 1 (between 0-9): ');
readln(Num1);
while (Num1 < 0) and (Num1 > 9) do
Begin
writeln ('Invalid number, enter a number between 0-9');
readln(Num1);
end;
write('Enter Number 2 (between 0-9): ');
readln(Num2);
while (Num2 < 0) and (Num2 > 9) do
Begin
writeln ('Invalid number, enter a number between 0-9');
readln(Num1);
end;
write('Enter Number 3 (between 0-9): ');
readln(Num3);
while (Num3 < 0) and (Num3 > 9) do
Begin
writeln ('Invalid number, enter a number between 0-9');
readln(Num1);
end;
write('Enter Number 4 (between 0-9): ');
readln(Num4);
while (Num4 < 0) and (Num4 > 9) do
Begin
writeln ('Invalid number, enter a number between 0-9');
readln(Num1);
end;
writeln;
end; // End of Parameters of Numbers and Messages

Begin // Comparing Ran1 with Numbers
Counter := Counter + 1;
If Ran1 = Num1 then
Begin
write('X ');
End

Else if
Ran1 = Num2 or Num3 or Num4 then
Begin
write('0 ');
End

Else write('_ ');

End; // End of comparing Ran1 with Numbers

Begin // Comparing Ran2 with Numbers
If Ran2 = Num2 then
Begin
write('X ');
End

Else if
Ran2 = Num1 or Num3 or Num4 then
Begin
write('0 ');
End

Else write('_ ');

End; // End of comparing Ran2 with numbers

Begin // Comparing Ran3 with numbers
If Ran3 = Num3 then
Begin
write('X ');
End

Else if
Ran3 = Num1 or Num2 or Num4 then
Begin
write('0 ');
End

Else write('_ ');

End; //End of comparing Ran3 with numbers

Begin //Comparing Ran4 with numbers
If Ran4 = Num4 then
Begin
write('X ');
End

Else if
Ran4 = Num1 or Num2 or Num3 then
Begin
write('0 ');
End

Else writeln('_ ');
writeln;
End; //End of comparing Ran4 with numbers

End; // End of comparing random numbers and users numbers

procedure Results_of_code (counter: integer); // Displays results of Codebreaker
begin
writeln ('Number of guesses taken:', counter + 1);
end; // end of results

Procedure ExitScreen;
Begin
writeln ('******************************');
writeln ('* Thank you for playing *');
writeln ('******************************');
write ('Press enter to Exit. ');
readln;
end;

//****** Main Program Starts here******
Begin
WelcomeScreen (Counter);
Generate_Random_Number (Ran1, Ran2, Ran3, Ran4);
Repeat
User_Input_and_Comparing_Random_and_Guess (Counter, Ran1, Ran2, Ran3, Ran4, Num1, Num2, Num3, Num4);
Until (Ran1 = Num1) and (Ran2 = Num2) and (Ran3 = Num3) and (Ran4 = Num4);
ExitScreen;
readln;
End.

[Hint] StudProg2.dpr(34): Value assigned to 'Ran4' never used
[Hint] StudProg2.dpr(33): Value assigned to 'Ran3' never used
[Hint] StudProg2.dpr(32): Value assigned to 'Ran2' never used
[Hint] StudProg2.dpr(31): Value assigned to 'Ran1' never used
[Hint] StudProg2.dpr(73): Value assigned to 'Counter' never used
[Warning] StudProg2.dpr(156): Variable 'Ran1' might not have been initialized
[Warning] StudProg2.dpr(156): Variable 'Ran2' might not have been initialized
[Warning] StudProg2.dpr(156): Variable 'Ran3' might not have been initialized
[Warning] StudProg2.dpr(156): Variable 'Ran4' might not have been initialized
[Warning] StudProg2.dpr(158): Variable 'Num1' might not have been initialized
[Warning] StudProg2.dpr(158): Variable 'Num2' might not have been initialized
[Warning] StudProg2.dpr(158): Variable 'Num3' might not have been initialized
[Warning] StudProg2.dpr(158): Variable 'Num4' might not have been initialized

Next time, please post your code within [code] and [/code] tags to make it easier to read. As for those messages, none of them are errors, they are all warnings. Also, the messages are fairly self-explanatory and even include the line # where the problem is.

I'll give you a hand as to what the messages mean, but you'll need to fix the warnings yourself:
"[Hint] StudProg2.dpr(xxx): Value assigned to 'yyy' never used" -- This means that you're assigning a value to a variable yyy on line xxx, but never using the variable yyy in any expression afterwards. This means that the assignment statement is useless, since you never use yyy for anything.

"[Warning] StudProg2.dpr(xxx): Variable 'yyy' might not have been initialized" -- This means yyy is being used in an expression without being initialized properly.

These two warnings are related. You're attempting to set the values of the variables in a procedure, but you passed the variables by value, instead of by reference. Hence, any changes you make to the variables within Generate_random_number, do not affect the variables outside it. You should pass the values by reference (using var) and then it'll make all the hints/warnings go away.