parameter/variable passing && void func(); (please help me...PLLLEEEAAASSSEEE!)

Ok here is my question. How do you make subroutine things, and how do you pass the variables so you can use them in different subroutines? Ok, the following is an example that illustrates using subroutines/functions, and it is in need of variables being passed/parameters. Even though I could easily do it without the subroutines, I did it like this so I get how to do it. I made it so things need to be passed from subroutine to subroutine, main to subroutine, and subroutine to main. Could someone please copy this code and make all necessary changes (like variable passing and correct use of subroutines/functions) to make it work? Thanks, this would help me a lot and I could finally fix my awesome program.

void func1(); //Do I need to do this? Prototype?
void func2(); //Same thing...?
void func3();
void func4();

int main()
{
int aa, ab, ac;
func1();
p=99;
func2();
func3();
cout<<x<<y<<z;
cout<<a<<b<<c;
int gx=sum2*5
func4();
cout<<gh;
cout<<cd;
cout<<ab;
return 0;
}

//FUNCTION DEFINITIONS

void func1() //Function definition? Must I do this?
{
int x, y, z, p;
x=56;
y=34;
z=2;
}

void func2()
{
int gh=p+x+z;
aa=45;
int sum=x+y+z;
char a='hello user' // <-- Is that the right type of quotes?
int b=99;
int c=10;
sum1=b+c;
}

void func3()
{
ab=55;
cout<<sum<<a<<x;
int sum2=sum+sum1;
}

void func4()
{
ac=ab+aa;
cout<<gx<<a<<x<<sum1;
int cd=70;
gh=gh*2;
}

The functions you've created will work but won't really do anything. They don't return anything (void) and the argument list is empty (func1( ) ).

First:
Let's change void func1( ) to int func1( int nValue ). And let's say func1 returns double the value of any value it is passed.

Second:
Let's change void func2( ) to void func2( int * pValue ). Where func2 will double the value of the integer pointed to by pValue.

Code:

int func1( int nValue ); // declaration
void func2( int * pValue ); //declarartion

int main( )
{

  int n = 10;

  int nNew = func1( n ); //nNew will equl 20 and n will stay at 10
  int *pNew = &nNew;  // assign nNew to pNew
  func2( pNew ); //when this returns nNew will be 40

  return 0;

}

int func1( int nValue ) //definition
{
   return nValue * 2;
}

void func2( int * pValue ) //definition
{
   *pValue *= 2; //* dereference pValue and double what it points to.
}

And the question about char a='hello user' // <-- Is that the right type of quotes? won't work.

Try char a[] = "hello user"; // this will create an array of 11 chars 10 for the text and 1 to null terminate the string.