+=
From Microduino Wiki
+=(Compound addition)
*Description
Arithmetic operator used between variables or constants. "+=" is an abbreviation.
*Syntax
x += y; // It is equal to x = x + y; x -= y; // It is equal to x = x - y; x *= y; // It is equal to x = x * y; x /= y; // It is equal to x = x / y;
*Parameters
x: Variable in any data type
y: Variable or constant in any data type
*Example
x = 2; x += 4; // x = 6 x -= 3; // x = 3 x *= 10; // x = 30 x /= 2; // x = 15