creating a simple computer

Define the word "simple"

If ur needs are +,-,*,/ then u can make it using elctronics components like trnasistors,op-amps, restistors,

If ur need "simpl"icity increases. number of the components increases, a better way is to make it compact by (miniaturisation )& call it as IC.

Rgds Vipin

The concept of the arithmetic-logic unit (ALU) is independent of microprocessor ICs. You can make an ALU and support circuitry (definition of a microprocessor) out of discrete transistors, vacuum tubes, or even relays:

Note that the memory on the relay computer in the link is a SRAM IC, rather than relays. That's primarily because each bit of relay memory, like each bit of valve, transistor or IC mask memory, is boring and repetitive, takes a lot of space, and you need an awful lot of them. This also makes it easier to load a program.

As to why, you would have to ask yourself. There's no real world advantage in doing it in any of the above ways.

I would guess the relay computer above was done as a teaching tool to show that the ALU concept is independent of an IC process. Things have come a long way since ENIAC. If you want to play, get a development system for a PIC, and have fun. There's a lot more rewarding stuff to do than reinvent the wheel.

Good luck Chris

... about 40 million years ago, there was a computer named ENIAC - no microprocessor. I even built a "simple" computer when my kids were small that would convert (4) binary switches (on/off) to a decimal equivalent number on a seven segment display. Yes, it's possible to create a computer without a microprocessor now-a-days but, why would you want to? If you "need" a small computer, get a "BASIC Stamp". If you need a small "controller", get a small PLC - Panasonic (Aromat) makes several, low-cost versions.

willis0966

Sure. It was done in Nazi Germany. http://72.14.203.104/search?q=cache:zvftrCTqbF0J:en.wikipedia.org/wiki/Konrad_Zuse+Z3+*-relays+first-computer+zzz+Turing-*-computer+1941+conditional-jumps Foley already mentioned relays.

The Brits did it with vacuum tubes a few years later

--preceding ENIAC by just a bit. http://72.14.203.104/search?q=cache:FVezPbmJ23wJ:en.wikipedia.org/wiki/Colossus_computer+Bletchley-*+1943+vacuum-tubes+zzz+*-Flowers+electronic-valves+*-*-secret-*-remained-*-for-many-years (The transistor wasn't invented until 1947.) . .

To *create* one requires a knowledge of "digital logic". "Arithmetic Logic Unit" has already been mentioned.

You mention this and I start looking for my old SlideRule. I could not find it so how about an Abacus?

Great collection photos:

"Those who scorn computer history are those who really don't grasp what is happening today and will never really shape tomorrow."

-Don Congdon

Good Luck,

• * * Christopher

Temecula CA.USA

Links to homemade computers without microprocessors: