4.2. Initializing Variables¶
When you’re ready to give your variable a value for the very first time in your program, you will need to initialize it to said value. We can initialize the score and percentChange variables to values using the assignment operator (cough the equal sign cough). Now, our program will look like this:
1. int score;
2. double percentChange;
3. score = 100;
4. percentChange = 45.7;
As you can see, we are declaring the variables score and percentChange on line 1 and 2 of our program, and initializing them to the numbers 100 and 45.7 on lines 3 and 4 of the program. Here’s how your computer might interpret this program:
What if you want to change the value that is stored in your variable? No problema! We can change the values that are stored in variables by assigning our variables to new values (cough use the equal sign again cough). Our computer is happy to chuck the old value and replace it with a new one. Here’s what it might look like to assign our variables to new values1:
1. int score;
2. double percentChange;
3. score = 100;
4. percentChange = 45.7;
5. score = 200;
6. percentChange = 11.2;
I REALLY need you to notice that the values stored in score and percentChange are the MOST RECENT values assigned to the variables after program execution has completed. What makes something the most recent value? That depends on how many lines of code our computer has executed. If we were to ask this question right after our computer executed line 4 of the program above, then the most recent values of score and percentChange would be 100 and 45.7 respectively. Our computer has no awareness of what has happened or what will happen — it lives in the moment! So, the most recent assignment is the assignment which occurs closest to the most recent line of code that has been executed. If we assume the entire program has just been executed, then 200 and 11.2 would be the most recent values assigned to score and percentChange.
Ok, ok, so we can store numbers in our variables. Big deal. Can we store anything a little more complex in variables?
TL;DR
You will always follow this pattern when you need to initialize or assign your variable to a value:
name = value;
If you want to declare and initialize in a single line, you will follow this pattern:
type name = value;
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Initialize is only used to refer to the first value that is given to our variables. Assign is used to generally talk about giving variables values. It’s very much like the math saying of “every square is a rectangle but not every rectangle is a square.” Initialization is a form of assignment. Assignment is not a form of initialization.