C# Numbers and Operators

An operator is a symbol that asks C# to perform an operation on values. The values around it are operands. In price * quantity, the multiplication operator combines two operands and produces a new value; it does not alter either original variable unless you assign the result somewhere.

The remainder operator % returns what is left after whole-number division. 17 % 5 is 2. It is useful for testing even numbers, wrapping a position around a repeating range, or splitting a count into full groups and leftovers.

using System;

class Program
{
  static void Main()
  {
      int minutes = 135;
      int hours = minutes / 60;
      int remainingMinutes = minutes % 60;

      Console.WriteLine($"{hours} hours and {remainingMinutes} minutes");
  }
}

2 hours and 15 minutes

When both operands are integers, C# performs integer division and discards the fractional part. This is not rounding: 9 / 4 becomes 2 whether the discarded fraction is small or large. If a fractional result matters, make at least one operand a double or decimal before division.

This matters in averages. int average = total / count silently loses the fraction before it reaches average. Writing double average = (double)total / count converts total first, so the division can produce a fraction.

int completedTasks = 9;
int days = 4;

Console.WriteLine(completedTasks / days);          // 2
Console.WriteLine((double)completedTasks / days);  // 2.25

C# follows precedence rules: multiplication, division, and remainder happen before addition and subtraction. Parentheses run their inner expression first and make intended grouping visible. Even when the language would calculate the same result without them, parentheses can save the next reader from re-deriving the rule.

Compound assignment operators update a variable from its current value. score += 5 means score = score + 5. Increment and decrement, score++ and score--, change an integer by one. Prefer the form that makes the business operation obvious; compact syntax is not automatically clearer.

Displaying two decimal places does not change the stored value. When a rule actually requires rounding, call Math.Round and choose the precision deliberately. Financial and regulatory rules can specify a midpoint strategy, so do not assume every domain wants the same behavior.

Numeric types also have limits. An int cannot hold a value above int.MaxValue. In a checked context, overflow throws an exception instead of wrapping silently. Most beginner programs will not reach those boundaries, but counters, identifiers, and large multiplications should use a type chosen for their possible range.

decimal rawAverage = 10m / 3m;
decimal shownAverage = Math.Round(rawAverage, 2);

Console.WriteLine(rawAverage);
Console.WriteLine(shownAverage);