The Theory
The basics of computing theory and perhaps computer science comes from what is known as the 'adder'. Computers are great at adding, subtracting and all types of mathematics. Using the lightening fast speed of a computer and a simple logic circuit we can build a super fast calculating machine!
The Circuit
Below is a picture of the most basic of all adders. It's a 1-bit adder. Two 1-bit signals, A and B are sent into the adding circuit and added. So now, here is how it works:
0+0 = 0
0+1 = 1
1+0 = 1
1+1 = 0 + Carry Bit
If you compare the calculations above to the truth table in the picture above you'll see they're exactly the same. This is the essence of the simple half adder circuit. You can combine many together to create 2-bit, 4-bit, 8-bit & etc. adders. We'll be making a 4-bit adder but first let's take a quick look at hardware specifics.
The basics of computing theory and perhaps computer science comes from what is known as the 'adder'. Computers are great at adding, subtracting and all types of mathematics. Using the lightening fast speed of a computer and a simple logic circuit we can build a super fast calculating machine!
The Circuit
Below is a picture of the most basic of all adders. It's a 1-bit adder. Two 1-bit signals, A and B are sent into the adding circuit and added. So now, here is how it works:
0+0 = 0
0+1 = 1
1+0 = 1
1+1 = 0 + Carry Bit
If you compare the calculations above to the truth table in the picture above you'll see they're exactly the same. This is the essence of the simple half adder circuit. You can combine many together to create 2-bit, 4-bit, 8-bit & etc. adders. We'll be making a 4-bit adder but first let's take a quick look at hardware specifics.