Sections

• Introduction
• Using Operators with Outputs
• Order of Operations
• In Summary
• Practice Questions

Goal: Have computers be able to use operators and perform basic calculations.

Introduction

Computers are machines that are made to do calculations. In fact, they specialize in performing operations and manipulating any given data.

Operators are symbols that signal the computer to perform a task with a given value(s). An example of an operator in code is the << found in the cout command. Operators are able to add, assign, or compare values. This chapter will focus specifically on arithmetic operators, operators that take numbers and return a single numerical value.

In C++ (and most other languages), the + is used to add two numbers together. A line of code in which operators are used is called an expression. For example, 5 + 3 and 1 + 2 + 3 + 4 are considered to be expressions. When given an expression, the computer will always attempt to evaluate the expression and return a single numerical value.

Using Operators with Outputs

When putting operators onto an output command, arithmetic operators will naturally take priority over <<. This means that the computer will evaluate an expression between a set of << before outputting.

Example Code:

<span id="L1" class="line"><span class="cp">#include &lt;iostream&gt;</span></span>
<span id="L2" class="line"><span class="k">using</span> <span class="k">namespace</span> <span class="n">std</span><span class="p">;</span></span>
<span id="L3" class="line"></span>
<span id="L4" class="line"><span class="kt">int</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span></span>
<span id="L5" class="line">    <span class="n">cout</span> <span class="o">&lt;&lt;</span> <span class="s">"5 + 3 = "</span> <span class="o">&lt;&lt;</span> <span class="mi">3</span> <span class="o">+</span> <span class="mi">5</span> <span class="o">&lt;&lt;</span> <span class="n">endl</span><span class="p">;</span></span>
<span id="L6" class="line">    <span class="mi">4</span> <span class="o">+</span> <span class="mi">4</span><span class="p">;</span>             <span class="c1">// semicolon</span></span>
<span id="L7" class="line">    <span class="k">return</span> <span class="mi">0</span><span class="p">;</span></span>
<span id="L8" class="line"><span class="p">}</span></span>

Output:

5 + 3 = 8

In the output statement in the code above (Line 5), the computer will first output the text 5 + 3 = . Since the + is enclosed with quotations, the symbol is considered to be a character in text and not an operator. In the next portion of the output statement, there is an expression in which 3 and 5 are added. The computer will first evaluate the expression and result a number (In this case, it would be 8). Then, it will output that number onto the screen. Once done the output statement, the computer will then evaluate 4 + 4 located on the next line. However, the calculation is useless as the computer has nothing to do with the number returned from the expression. Thus, the computer simply continues to the next line of code.

NOTE: Arithmetic Operators are not meant for text. Do not try to add or subtract text in a code file using these operators. Definitely do not think about adding text with numbers.

Below is a list of some arithmetic operators (and more) available for C++.

Name	Syntax	Description	Example	Output
Addition	+	Adds two numbers together	8 + 3	11
Subtraction	-	Subtracts two numbers together	8 - 3	5
Multiplication	*	Multiplies two numbers together	8 * 3	24
Division	/	Divides the first number by second number (Will drop the remainder when dividing integers)	8 / 3 8.0 / 3	2 2.66667
Modulo	%	Finds the remainder when first num is divided by the second number	8 % 3 9 % 3 9 % 4	2 0 1
Parenthesis	()	Dictates the order in which operations are done. Prioritizes all operators inside parenthesis. Technically not an arithmetic operator.	2 * (8 - 3)	10

A list of these operators and more are found in List of Operators doc shared with you.

Order of Operations

Generally, the order of operations for arithmetic operators will be similar to BEDMAS/PEMDAS. Division, multiplication, and modulo will typically be executed before addition or subtraction. However, adding parenthesis to an expression will help ensure that the expression will always run the way that it is intended to. There is no consequence for putting excessive amounts of parenthesis in an expression (Other than readability).

Click here to see a chart displaying the order of operations.

In Summary

• Operators are symbols that manipulates data values

• Arithmetic Operators are operators that deal with numeric values

• An expression consists of a combination of numbers and arithmetic operators

• Expressions are able to be placed within an output statement

• Parenthesis are used to change the order in which operators are performed

Practice Questions

• Create a program called 42.cpp. Since 42 is the answer to life, the universe, and everything, your job is to have your code output the number 42 in five different ways, using each operator at least once.

• Jimbob, being the beginner that he is, is confused on why his code outputs -1 and not 2. Your goal is to add parenthesis to Jimbob’s code in order for his code to output 2.

  #include <iostream>
  using namespace std;
  
  int main(){
      cout << 14/6+4/5%8-3;
      //arithmetics are hard
      return 0;
  }