Comparison operators

Learn to compare values with ==, !=, <, >, <= and >=.

Logical operators

With logical operators you combine multiple conditions: && AND, || OR, ! NOT. All of them produce a bool value.

For example, entering a cinema requires age 18 or older AND a ticket: (age >= 18) && hasTicket. Both conditions must be true for the result to be true. With ||, a single true is enough.

Short-circuit evaluation

The && and || operators short-circuit: if the left side already decides the result, the right side is never evaluated. false && x is false; x is not computed.

This is especially useful to avoid errors like division by zero. Writing (divisor != 0) && (number / divisor > 1) means the second condition is skipped when the divisor is zero, so the program does not crash.

Exercise Write the entry condition

Write an if with the condition (age >= 18) && hasTicket. Print "allowed" when true and "denied" when false. You must use an else branch and the && logical operator.

Show example solution

For the condition, write if ((age >= 18) && hasTicket) { ... } else { ... }.
Example solution:
using System;

class Program
{
    static void Main()
    {
        int age = 20;
        bool hasTicket = true;
        // Write the condition and print
        if ((age >= 18) && hasTicket)
        {
            Console.WriteLine("allowed");
        }
        else
        {
            Console.WriteLine("denied");
        }
    }
}

Test yourself

Match each operator to its meaning

&&

And (logical)
||

Or (logical)
!

Not
&

And (bitwise)
n = 5; bool ok = (n > 10) && (n++ > 0); Console.WriteLine(n); what is the output?
```
int n = 5;
bool ok = (n > 10) && (n++ > 0);
Console.WriteLine(n);
```
- 6
- 0
- True
- 5
Show answer

5 — Correct. n > 10 is false so short-circuit kicks in; n++ is not evaluated and n stays 5.

Write the logical AND operator

int age = 20;
bool ticket = true;
bool ok = (age >= 18) ____ ticket;
Console.WriteLine(ok);

Show answer

int age = 20;
bool ticket = true;
bool ok = (age >= 18) && ticket;
Console.WriteLine(ok);

Next lesson: Logical operators

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