Basic Math

Addition, subtraction, multiplication and division are some of the most basic tasks you will perform as a programmer. In fact, doing math is so common in programming that shortcuts have been developed to represent certain mathematical operations.

Operator	Description	Example
+	addition	5 + 3
–	subtraction	4 – 3
*	multiplication	8 * 2
/	division	4 / 2

Below is a simple example of how to add two integer numbers. At the end of the program, value printed out should be 8.

You can also do math as part of assigning a value to a variable. For example, if you wanted to add five to a value held by a variable, you can do the following:

int i = 4; 
i = i + 5; 
print(“ i is: ” + i); 

The above computation takes the current value held by the variable “i,” adds 4 to it, and then puts the new value back into “i.” At the end of the program, “i” should be 9. This type of computation is so common that a shortcut was developed to make it less cumbersome for programmers to write.

Operator	Same as	Example
+=	x = x + 4	x += 4
-=	x = x – 2	x -= 2
*=	x = x * 5	x *= 5
/=	x = x / 2	i /= 2

The most common computation that programmers do is adding 1 and subtracting 1 from a value. In fact, this operation is so common that there are special operators called the increment (++) and decrement operators ( — ) to make adding 1 and subtracting 1 easier to write.

For example, the following program adds 1 to 6, and should print 7.

int number = 6; 
number++; 
print(“number is: ” + number); 
</div>
<div class="output">
number is 7
</div>
<p><div class="note">Decrementing</div> The next program subtracts 1 from 6, and should print 5.</p>
<div class="code">
int number = 6; 
number--; 
print(“number is: ” + number); 
</div>
<div class="output">
number is 5

Operator	Same as	Example
++	x = x + 1	x++
—	x = x – 1	x–