How Did Vacuum Tubes Revolutionize Early Computers?

[jd12345]

Today computer hardware is based on integrated circuits. Its based on digital logic and use transistors etc...(i am not an expert)
But looking on the history of computer hardware- First computers were all mechanical which I understand because of lack of technology. And after than computer were based on vacuum tubes. I don't understand what are these. What are vacuum tubes and how can they be used to make a computer?

I understand todays technology, we have gates which can manipulate binary signals and using this we can do various stuff. But what's the basic idea behind vacuum tubes and earlier technologies? How did they work?

 

[Borek]

Vacuum tubes are - in a way - analogous to the semiconductor elements. Just like you can build your circuit from semiconductor diodes and transistors, you can build the circuit from the vacuum tube diodes and triodes (or tetrodes, pentodes...). Yes, they are different, and it is not just a matter of replacing one with the other, but on the very general level there is no difference - you have active elements with known properties, and they can be used as building blocks.

 

[jd12345]

Well are vacuum tubes very complicated electric devices because I didn't study them in my school whereas I did study semiconductor devices.
Can you give some examples of basic operations that these vacuum tubes can do? Like semiconductor devices - the most basic things they can do are:- performing and, or operations on two binary signals.
Also if possible can you just give the idea behind how these vacuum tubes work?

Thank you!

 

[rcgldr]

Wiki article that includes some mention of vacuum tubes:

http://en.wikipedia.org/wiki/Logic_families

There are pdf links from this wiki article about the IBM 604 that contains a lot of information (the customer engineeering manual is 261 pages long):

http://en.wikipedia.org/wiki/IBM_604

 

[Borek]

They are quite simple. Start with wikipedia, I believe it contains enough information.

Basically it is a vacuum tube (as the name implies) with electrodes planted inside. One of the electrodes - cathode - is heated up to emit electrons (which is why vacuum tubes based radios had to warm up before starting to work). Other electrodes are there to to collect the electrons (anode) and to control the flow of the electrons. For example in triode applying voltage to the controlling electrode (which is placed between anode and cathode) you can control the current between the anode and the cathode.

Edit: I see rcgldr posted while I was editing.