An adder takes two numbers, adds them, and the result is the sum of the numbers. In digital electronics, calculators, computers, etc., numbers are represented in a binary code. A digital adder is capable of adding two binary numbers.

Digital adders are used everywhere where
calculations must be performed.
Think of processing units of a **microprocessor**.
Adders form the core of these units,
called **A**rithmetic **L**ogic **U**nits **(ALU)**.

If you want to know what adders are,
how they work and where they are used,
this is the right place.
With **C-MOS logic IC's** you build simple adders,
and expand them.
For adders means not only those that add two binary numbers,
but also those that **subtract**, **multiply**
and **divide**.

Another issue is **speed**.
Adder must be able to process a large amounts of number.
Hence, the speed at which the adder calculates the numbers,
is very important.
Here, you get to know the most **important circuits**.

To get started you need to do a few **preparations**...