The ALU(Arithmatic logic unit) is what is going to do the math. Note that each adder you build will double the capacity of numbers it can add.
Step 1: More Bits
You can add more bits if you want, adding on like so. Each bit adds double the amount of numbers it can store. I only did two for the simplicity.
Step 2: Inputs and Outputs
The yellow clay represents inputs, the back of the bit has two redstone, which is your output. Later more details will be added.
Step 3: Starting Memory
This is the first step in building memory. Remember last step, when we talked about the two redstone at the back of the bit? Well that's where it'll lead to our memory.
Step 4: Addition/subtraction Control
This is how we choose whether or not we want output, you might not need it if you aren't doing subtraction(which will be in a another tutorial), but basically this is how you'll choose between addition and subtraction later on.
Next you want to invert it one more time and build a 1x2x1 staircase up like so. Note that the amount of these staircases depends on how many bits you have in your ALU
Next place torches like so, two blocks side ways and two blocks back, like so. Again, the amount of torches depends on how many bits you have. I only have two, so I only use two lines for the data bus, which is that long block line.
Step 7: D Flip-flop
Also, note that the top redstone must be on at first. This can be solved by breaking the redstone that is on the ground and replacing it. If that doesn't work, you're probably doing it wrong. The lever is how you write code into memory, just input something in your ALU and flip the lever twice.
Step 8: Display Pt.1
Then you want to draw the wires out and make that design. Also, as you can see I added another d flip flop.
Step 9: Display Pt.2
These lines will allow you to read the memory that is stored in the d flip flop.
Step 10: Reading Command
This is the part of the computer that will allow you to read the memory. Each piece controls one d flip flop.
Step 11: Overview So Far
This is what your memory should look like now.
Step 12: Example Display
This display show the number one.
Step 13: ALU Numbering
This is something I should have done at the beginning, but here it is. The first three levers are 1s. After that, every two levers doubles the number.
1 1 1 2 2 4 4 .etc
Step 14: Thanks for Reading
Thanks for taking your time to read this, I hope it was helpful and educational. Hopefully you get the point and actually understand it if you build it. Please comment so I can get feedback on how to improve these tutorials and if you really enjoyed it, favorite it.