Basic Arithmetic Circuits To understand binary, one needs to understand some of the basic circuits that are inherent in carrying out arithmetic functions within a computer. So, now we will introduce some simple notions of basic addition and subtraction circuits.
One simple circuit adds two single binary digits. Two inputs are required, and it produces two outputs: one which displays the result of the addition, another showing whether there is an overflow which should be carried to the next higher bit.
An improved version of the above circuit takes three inputs, instead of two. Its outputs are similar to the previous one-output-the sum and overflow indication-so that larger addition jobs can be handled with it.
These are binary subtractors, designed to subtract one binary digit from another, taking two input signals and producing two output signals-one the result of subtraction, the other indicating whether or not there will be a borrowing from the next bit.
An enhanced version of the subtraction circuit takes three inputs. It also produces two outputs-one bearing information about the result of the subtraction and the other signaling whether borrowing for the next operation is called for:.
In other words, such basic adder and subtractor circuits form the very foundation of binary arithmetic. They impart the ability to conduct basic arithmetic functions to computers and thus lay a fundamental framework for other complicated functions of digital systems.