You can increase the value of a variable a by 4, for example, with
If beforehand a were equal to 4, it would now be equal to 8. A shorthand way of doing this is with the += operator;
will also increase the value of a by 4.
Similar shorthands exist for subtraction, multiplication and division. If a is equal to 8 and you enter
then a will be equal to 6. If you follow this with
then a will be equal to 18, and finally
will end with a equal to 2.