The C++ conditional operator is also known as a ternary operator because it takes three operands.  How this operator functions is somewhat similar to an if statement or a switch statement, but in a more compact form and for one single Boolean value with one of two possible outputs.   That is to say, the first operand is evaluated as a Boolean result.  If the result is true, then the second operand will be the one evaluated.  Otherwise, the third operand will be evaluated.   A sample helps amplify this.

#include <iostream> 
using namespace std; 
int main() 

     int i = 1, j = 2; 
     cout << ( i > j ? i : j ) << " is greater." << endl; 

In this example, we have two integer variables, i and j which are initialized to 1 and 2 respectively.  The ternary operator is embedded inside the cout statement and essentially follows this pattern:

  1. it checks whether i is greater than j
  2. it outputs the proper numeric value along with is greater.

In the code example here, j is greater than i so the condition evaluates to false and the value for j (2), is output to the console along with the text is greater.  In other words, the output is "2 is greater."  If i was 5 and j was 2, the output would be, "5 is greater." 

i > j ? i : j where i is greater than j then the bold value is selected

i > j ? i : j where j is greater than i, then the bold value is selected

This contents come from : Introduction to C++

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