In part 5 you learned about memory concepts. In this article we will go through some basic arithmetic in C++. Table 1 below summarizes the C++ arithmetic operators.

Operation | C++ Operator | Example |

Addition | + | x + y |

Subtraction | - | x - y |

Multiplication | * | x * y |

Division | / | x / y |

Modulus | % | x % y |

* Table 1*

When you create a variable, you can actually use basic arithmetic like this:

```
int x = 10 + 10;
std::cout << x;
```

The compiler will first calculate 10 + 10, and then assign our variable the result of this calculation. Therefore, when we run this program it will output 20. In the same way, if we change our + sign to -, the output will be 0, since 10 - 10 is 0.

To perform multiplications, use the asterisk (*).

```
int x = 5 * 2;
std::cout << x;
```

This will output 10. If we use the same example with division, the output should be 2.5, true? False. Our variable x is declared as an **integer**, and integers only hold integers, any fractional part is discarded. No rounding occurs. To get the remainder after integer division, C++ provides the modulus operator (%). This operator can only be used with integer operands. Consider the code:

```
int x = 5 % 2;
std::cout << x;
```

The remainder of 5/2 is 1, so the output here will be 1.

The same **rules of operator precedence** that's in algebra hold in C++. This means that operators in expressions contained within pairs of parentheses are always evaluated first. Multiplication, division and modulus operations are applied next. These are applied from *left to right* if an expression contains several multiplication, division and modulus operations. Addition and subtraction are applied last, and are also applied from *left to right*.

In algebra it's common to put two variables next two each other when multiplying. This cannot be one in C++, every time we want to multiplicate two variables, we have to put the multiplication operator between them (*). Take the straight line as an example:

**Algebra: **

**C++: **

`y = m * x + b;`

In the next article we will learn about functions and namespace. Read C++ 7. Functions (and namespace) here.

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2018-11-05

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