lab4.cpp Code Syntax and Algorithm Check

Is this correct?  Please advise.  Del
*******************************Actual Code*********************************
#include <iostream>
#include <iomanip>
#include <cstdlib>
#include <ctime>
#include <cmath>

int biggest(const int, const int, const int);
int gcd(const int, const int);
void addBlanks(){};
double round(const double);


int main() {

  rand();
  srand(time(0));
  time(0);

  int x, y, z, randOut, srandOut;
  cout << "Enter three integers. " << endl;
  cin >> x >> y >> z;

  cout << "The biggest of " << x << "," << y << ", and " << z << "is " << biggest(x,y,z) << endl;
  cout << "The greatest comon divisor of " << x << " and " << y << " is " << gcd(x,y) << endl;
  cout << randOut << " is a random number. " << endl;
  cout << srandOut << " is a seeded random number. " << endl;
  cout << "The rounded number is " << round(floatNum) << endl;

  return 0;

}

int biggest(const int x, const int y, const int z) {
 
  int size;
  if((x < size) && (y < size) && (z < size))
    return size;

}

int gcd(const int x, const int y) {
   
   int remainder = x % y;
     if(remainder != 0)
     return gcd(remainder, x);
    return x;

}

void addBlanks() {

  //generate random #, print digits seperated by 5 spaces
 
  double firstDigit = digit;
  for(int digit = 4; digit >= 0; digit--)
    cout << firstDigit << " ";

  return;

}

double round(const double floatNum) {

  //round parameter to the nearest int
  floor(floatNum);
  pow(floatNum,);

}

**************************************************************************************
 
output:

lab4.cpp: In function `double round(double)':
lab4.cpp:67: parse error before `)'
 
I am not sure on addBlanks() and double round()...please advise.

Description of the problem below:
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PART I.
Write function definitions for the following prototypes:

int biggest(const int, const int, const int );
// Returns the largest of three integers.

int GCD( const int, const int );
// returns the greatest common divisor (GCD) of two integers, where GCD is the largest integer that divides both of them evenly.

void addBlanks ( );
/* produce a random integer between 1 and 32767 and print it as a series of digits, where each digit is separated by a space; e.g. 4562 should be printed as: 4 5 6 2 (text 3.25(c) pg 244)*/

PART II.
Write the prototype, definition and call for a function that will take a local double from main and round it to its closest integer value; e.g. 3.45 will become 3.00, and any number >= 3.5 will become 4.00. See pg. 242 Exercise 3.13 for help. The function should modify the value of the double in main.