# Operators

Let’s learn some important terms before moving forwards. An operation sign like `+` is called an operator. It’s just a symbol that produces a certain operation. Later you’ll learn that there are other operators in PHP, than just arithmetic ones.

``````<?php

print_r(8 + 2);``````

In this example `+` is an operator, and numbers `8` and `2` are operands.

In case of addition there’re two operands: one on the left, one on the right from `+`. Operators that require two operands are called binary. If you skip at least one operand, like so `3 + ;`, the program will exit with an error.

There are also unary operations (with one operand) and even ternary (with three operands)!

Symbols + and - are used not only as operators. As far as negative numbers are concerned, the minus sign becomes part of the number:

``````<?php

print_r(-3); // => -3
// The same as 4 - 3
print_r(4 + -3); // => 1``````

The plus sign can work in the same way:

``````<?php

print_r(+3); // => 3
print_r(1 + +3); // => 4``````

## instructions

Write a program that calculates the difference between `6` and `-81`, and prints the result to screen.

### definitions

• Arithmetic operator — addition, subtraction, multiplication, division.

• Operator — special symbol that creates an action. For example, `+` creates addition.

• Operand — that what is being used with an operator. `3 * 6`: here 3 and 6 are operands.

• Unary operation — operation that requires one operand.

• Binary operation — operation that requires two operands.

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