## Key Concepts

Review core concepts you need to learn to master this subject

### Variables

// Declare a variable
int score;

// Initialize a variable
score = 0;

A variable refers to a storage location in the computer’s memory that one can set aside to save, retrieve, and manipulate data.

Variables
Lesson 1 of 1
1. 1
The “Hello World!” program simply writes to the screen. It does not read anything, calculate anything, or allow for user input. That’s no fun! Real programs tend to produce results based on some …
2. 2
“Every variable in C++ must be declared before it can be used!” Suppose we are building a game and we want to keep track of a player’s score that goes from 0 to 10. We need a variable! Before w…
3. 3
After we declare a variable, we can give it a value! Suppose that we have declared an int variable called score, to set it to 0, we can simply write: score = 0; - The score is the name of the v…
4. 4
We can both declare and assign a value to a variable in a single initialization statement. Suppose we have these two lines: // Declare a variable int score; // Initialize a variable score = 0; …
5. 5
Computers are incredible at doing calculations. Now that we have declared variables, let’s use them with arithmetic operators to calculate things! Here are some arithmetic operators: - + additi…
6. 6
Now that we have outputted a variable and have also outputted things using multiple couts. Let’s take a closer look at cout again. If we have the code below: int age = 28; std::cout << “Hello, …
7. 7
Like we mentioned in the introduction, another way to assign a value to a variable is through user input. A lot of times, we want the user of the program to enter information for the program. We h…
8. 8
Now that we’ve learned about the basics of variables and cin, let’s write a program! The mad scientist Kelvin has mastered predicting the weather in his mountain-side meteorology lab. Recently, K…
9. 9
Let’s go back to the temperature.cpp that we wrote. This time, instead of giving tempf a value of the current temperature in New York: tempf = 83; Let’s ask the user what the temperature is …
10. 10
You made it to the end of the lesson! High five. 🙌 Here is a review of the lesson: - A variable represents a particular piece of your computer’s memory that has been set aside for you to use to s…

## What you'll create

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## How you'll master it

Stress-test your knowledge with quizzes that help commit syntax to memory