Adding set of generated random numbers

[jp0424]

Hi everyone. First time here in bytes, but, I have a problem here dealing with adding a generated set of random numbers. Here is the code. And I recommend that you guys run it to see what I'm talking about.

 #include <iostream>
 #include <iomanip>
 #include <cstdlib>
 #include <cmath>
 
 using namespace std;
 //declarations
 int seed, n, lower, upper, num;
 double sum1, sum2, avg;
bool repeat = true;
 
 //function prototypes
void getParameters(int& seed, int& n, int& lower, int& upper);
int getNum(int lower, int upper, int n, int seed);
void update(int num, double& sum1, double& sum2);
//void output(double avg, double std);
 
 int main (){
     char input;
     do {
      getParameters(seed,n,lower,upper);
      getNum(lower, upper, n, seed);
      update(num,sum1,sum2);
      //output(avg, std); 
     cout<<endl;   
     cout<<"Enter Y or y to repeat, N or n to exit. ";cin>>input;
     }while(input == 'Y' || input == 'y');
     if (input == 'N' || input == 'n') repeat = false;
 system ("pause");
 return 0;
 }
 
/***************************************************************
The function gets the seed, size, upper, and lower bounds used
to generate the random numbers.
***************************************************************/
void getParameters(int& seed, int& n, int& lower, int& upper){
  cout<<"Seed for random number generator: ";cin>>seed;
  cout<<"The size of the sequence: ";cin>>n;
  cout<<"Lower and upper bound for the random number:";cin>>lower>>upper;
}
 
/***************************************************************
This function generates the random numbers based on the user input.
***************************************************************/
int getNum(int lower, int upper, int n, int seed){
    int i, a;
cout<<"The numbers generated are: "<<endl; 
srand(seed);   
for (i = 1; i <= n; i++){
    a=(rand()%(upper-lower)+lower);
cout<<setw(4)<<a;
}
cout<<endl;
return a;
}
 
/***************************************************************
This function should add up all the random numbers (sum1), and 
square it (sum2).
***************************************************************/
void update(int num, double& sum1, double& sum2){
 
     }
/***************************************************************
This function will output the average and standard deviation
using the values from sum1 and sum2.
***************************************************************/
//void output(double avg, double std){
//     }
 

Okay so here's the deal. If you run it, it's pretty straightforward. Program asks the user for the seed, upper and lower bounds, and size of the sequence to generate the random numbers. Thing is, as seen in my getNum function, I assigned the "randomizing" equation to a variable a. Now in the update function, I need to get the sum of those values (generated in getNum) to move on to the next phase of my coding (average and standard dev). My question is, is it possible to find the sum in getNum inside the update function? Am I even doing it the right way? Because it generated a set of values, because then these values are assigned to one variable, which I know is totally impossible, because one variable should only store one value. So I'm pretty much stuck. Also, most of the codes that I've seen while finding a solution is assigning the rand() to different variables, and then adding the values in those variables. Still don't get it? Okay, the codes that I've seen are, let's say:
a=rand(); equals some random value
b=rand(); equals some random value
c=rand(); equals some random value
sum = a+b+c;
Mine is:
(In getNum function)
a=rand(); equals multiple random values (because there's a for loop involved)
(In update function)
sum=?? (how to add these values??) <-- and finding the sum is in another function
Is my procedure kinda right? Or do I have to do the summation inside the getNum function and just "transfer" it to the update function? As an added catch, no arrays should be used. I know it's something simple, but for some reason I can't find the right operator or function or something for it. Anyways, here it is. Comments and suggestions are welcome. Thanks very much for helping. (Better get myself working again!!)

[Rabbit]

Use a separate variable to keep a running sum.

[jp0424]

yes, yes, yes, and thank you so much Rabbit. I was actually thinking on using the operator "+=" on this problem, but I was having doubts. I dug up some info about the running sum that you recommended and it used the operator "+=", so that pretty much solved my problem there. I'll post the complete working code, for future references to other users. That's it and thanks again.

[jp0424]

So here is the final code. Feel free to test this and salvage any codes that you wish to use in your codes.

 
 #include <iostream>
 #include <iomanip>
 #include <cstdlib>
 #include <cmath>
 
 using namespace std;
 int seed, n, lower, upper, num=0;
 double sum1, sum2, avg, total=0, stn;
 bool repeat = true;
 //function prototypes
void getParameters(int& seed, int& n, int& lower, int& upper);
int getNum(int lower, int upper, int n, int seed);
void update(int num, double& sum1, double& sum2);
void output(double avg, double stn);
 
 int main (){
 
     char input;
     do {
      getParameters(seed,n,lower,upper);
      getNum(lower, upper, n, seed);
      update(num,sum1,sum2);
      output(avg, stn); 
     cout<<endl;   
     cout<<"Enter Y or y to repeat, N or n to exit. ";cin>>input;
     }while(input == 'Y' || input == 'y');
     if (input == 'N' || input == 'n') exit (1);
 system ("pause");
 return 0;
 }
 
/***************************************************************
The function gets the seed, size, upper, and lower bounds used
to generate the random numbers.
***************************************************************/
void getParameters(int& seed, int& n, int& lower, int& upper){
  system("cls");
  cout<<"Seed for random number generator: ";cin>>seed;
  cout<<"The size of the sequence: ";cin>>n;
  cout<<"Lower and upper bound for the random number:";cin>>lower>>upper;
}
 
/***************************************************************
This function generates the random numbers based on the user input.
***************************************************************/
int getNum(int lower, int upper, int n, int seed){
    int i, a=0;
cout<<"The numbers generated are: "<<endl; 
srand(seed);   
for (i = 1; i <= n; i++){
    a=(rand()%(upper-lower)+lower);
    total+=a;
    num += (a*a);
cout<<setw(4)<<a;
}
cout<<endl<<endl;
}
 
/***************************************************************
This function adds up all the random numbers (sum1), and adds the
square of the individual numbers(sum2).
***************************************************************/
void update(int num, double& sum1, double& sum2){
     sum1=total;
     sum2=num;
     }
 
/***************************************************************
This function will output the average and standard deviation
using the values from sum1 and sum2.
***************************************************************/
void output(double avg, double stn){
     avg = sum1/n;
     stn = sqrt((sum2-(2*avg*sum1)+(n*avg*avg))/n);
     cout.setf(ios::fixed | ios::showpoint);
     cout.precision(2);
     cout<<"Average: "<<avg<<"      "<<"Standard Deviation: "<<stn;
     cout<<endl;
     total = 0;
     num = 0;
     }