Operations on variables
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Operations on variables
Summary
Changing the value of a variable
Here, we set the value of a variable named 'age' to 24:
age = 24;
We can also set the value of a variable when we define it:
int age = 25;
We can define many variables of the same type at once:
int day = 3, month = 7, year = 1994;
Mathematical operations
Let us define two variables:
int var = 5, var2 = 7;
Addition
Let us add them together:
var + var2;
The instruction above does not change the value of neither of the variables... It simply produces a result.
If we want to do something with the result, we must 'catch' it. Here we assign the result to a new variable:
int var3 = var + var2;
It is possible to add an = sign after the + to execute the addition and assign the result to the variable at once.
So, instead of that:
var = var + var2;
We can write that:
var += var2;
Incrementing and decrementing
The following:
var++;
Is a shortcut of:
var += 1;
And this:
var;
Is equivalent to:
var = 1;
Those shortcuts exist because adding/subtracting one to/from a variable happens quite often.
Multiplication and division
Multiplication and division work the same way as addition, except that the symbols are, respectively, * and /.
We multiply 'var' by 'var2':
var * var2;
We divide 'var' by 0.5:
var / 0.5;
Modulo
The modulo operation is a bit trickier (Only because it is less known). Its symbol is % and its result is the remainder of an integer division... So, for example, 5 % 2 equals 1, because 5 can be fully divided by 2 only two times and then, the remainder is 1 (5  (2 * 2)).
The variable 'var' modulo 7:
var % 7;
Operators and operands
The symbols used to execute operations on variables, like +, are called operators. The variable/value at the left of that symbol is called the left operand and the variable/value at the right is said to be the right operand.
Operations with variables of different types
When we execute operations on variables of different types, they are automatically converted:
int var1 = 50;
unsigned var2 = var1;
Above, 'var2' equals 50, but as a value of type 'unsigned'.
However, be careful. In some cases, a conversion may cause data loss.
For example, when a value of floatingpoint type is converted to an integer type, it loses the digits after its decimal point:
int var = 5.1234;
Above, 'var' equals 5.
Data loss can also arise if a value is converted to a type that is not big enough to hold it:
char var = 99999999;
Or if a negative number is converted to an unsigned type:
unsigned var = 5;