How to make a program output which number is the maximum and minimal?

Question

Hello. I understand that in this code line (a>b)?cout<<a:cout<<b; outputs a if a>b. But I'd like to understand what some things in this code line do.
Why is a ? needed after(a>b)
Why do we need a colon after a in <<a:cout<<b;
Why doesn't b need a colon too?
Isn't this code also saying to the program to output b?
Thanks in advance!
The program as it follows:
#include <iostream>
using namespace std;
int main()
{
double a, b;
cout << "Enter value for a:" << endl;
cin >> a;
cout << "Enter value for b:" << endl;
cin >> b;
cout << "a+b=" << a+b << endl;
cout << "a-b=" << a-b << endl;
cout << "a*b=" << a*b << endl;
cout << "(a+b)/2=" << (a+b)/2 << endl;
cout << "the max is ";
(a>b)?cout<<a:cout<<b;
cout << endl;
cout << "the min is ";
(a<b)?cout<<a:cout<<b;
cout << endl;
system("pause");
}

Answer 1

It's just the syntax. It's how it's written. It's a shortcut way of writing an if else statement.
Why do we need to write it with a ? and a : between both statements? Because who ever wrote the language thought it was a good idea. And I think it's pretty simple.
Basically, it's because whoever wrote the language said so.
(int1 < int2) ? cout << "condition is true" : cout << "condition is false";
This could also be written as:
if(int1 < int2)
{
cout << "condition is true";
}
else
{
cout << "condition is false";
}
Whoever wrote the language simply wanted to give us a shorter way to write things like this.
The ? tells us to check the previous condition in this case, and the colon is used to separate the "if true" condition from the "if false" condition.

Answer 2

This is called ternary operator. it's used to check condition just like if-else.
EXAMPLE :
if statement :
if(a < 2)
b = 5;
else
b = 4;
Equivalent ternary statement :
b = (a < 2) ? 5 : 4
EDIT: You can use if else for the given code as follows :
if (a > b)
cout << a;
else
cout << b;

Answer 3

Personally, the statement for max should have been coded:
cout<<(a>b)?a:b;
It makes use of the ternary result.