using cout and averages errors or bugs - c++

Question

I used Dev c++ 5.5.3 to write some programs. one of the programs is about getting some numbers (integer) until zero and then prints max, min , avg. In my computer everything is fine. in someone else computer, it does not show the right average and it shows very strange numbers 4.612521 e+8 and like this. I define a variable avg and calculate the value and then print it. The other one calculate the average directly when calling cout. can someone check This programs:
Program 1 which doesn't show the right answer:
#include <iostream>
using namespace std;
int main(int argc, char** argv) {
int n;
int max , min , count = 0 , s;
float avg;
cout<<"This program gets some numbers until zero and then prints maximum, minimum and average of them"<<endl<<"Please enter a number : ";
cin>> n;
max = n;
min = n;
while (n!= 0)
{
count ++;
s+=n;
if (n>max)
{
max = n;
}
if (n<min)
{
min = n;
}
cout<< "Please enter a number : ";
cin>>n;
}
cout<<"ZERO DETECTED!\n\n"<<endl;
cout<<"Maximum: "<<max<<endl;
cout<<"Minimum: "<<min<<endl;
avg = (float) s/count ;
cout<<"Average: "<<avg<<endl; // NOTE NOTE NOTE NOTE
return 0;
}
Program 2 which shows the right answer:
#include <iostream>
using namespace std;
int main(int argc, char** argv) {
int n;
int max , min , count = 0 , s;
float avg;
cout<<"This program gets some numbers until zero and then prints maximum, minimum and average of them"<<endl<<"Please enter a number : ";
cin>> n;
max = n;
min = n;
while (n!= 0)
{
count ++;
s+=n;
if (n>max)
{
max = n;
}
if (n<min)
{
min = n;
}
cout<< "Please enter a number : ";
cin>>n;
}
cout<<"ZERO DETECTED!\n\n"<<endl;
cout<<"Maximum: "<<max<<endl;
cout<<"Minimum: "<<min<<endl;
//avg = (float) s/count ;
cout<<"Average: "<<(float) s/count<<endl; //NOTE NOTE NOTE NOTE
return 0;
}

Answer 1

Both programs have undefined behaviour because s is not initialised and has not been assigned a value before you try to read from it for the first time:
int max , min , count = 0 , s;
[...]
s+=n;
All behaviour you have seen and the fact that it apparently "worked" on your computer and did "not work" on someone else's were more or less random occurrences.
Here's an easy fix:
int max , min , count = 0 , s = 0;
Note that your compiler should have warned you about the uninitialized variable. If not, then perhaps you should choose a higher warning level.
Also note that there are a lot of other flaws in your program, for example the use of using namespace std, that you declare multiple variables on the same line or that some of your variable names are not very descriptive.