(Once again, if you didn't get it the first time or maybe you came directly to this page somehow, we are demonstrating the OR gate in LOGIC to you people, so that you can get a start on your simple digital circuits and all that.)

Introduction: Boolean variables mean variables that can hold only two values, high and low (for example, high could be 1 and low could be 0).The OR gate is a logic gate that accepts two (or more, but let's stick with two in this example) inputs, and gives one output. This output is high (or 1) if at least one of the inputs is high (1). If both inputs are low (0), then and only then, the output is also low (0).
A table which includes all possible combinations of the input and the corresponding output in each case is called a TRUTH TABLE. It might look something like this, for a two input OR gate:
 
 

Input A	Input B	Output
0	0	0
0	1	1
1	0	1
1	1	1

You can see from this table that the output is high (1) if at least one of the inputs (A or B, thats why its called OR, you fool!) is high (1).
Boring? You think so? Well let's make things interesting...

If that doesn't make things clear to you, maybe we can give you an example. This particular example (thanks of course, to the great Subroto) is from the movie Paap Ki Duniya (for those of you who haven't seen this movie... shame shame, poppy shame, for those of you who have, high five!). For those of you who don't remember this movie, let me remind you of a song from this movie:

Main tera tota, tu meri maina
Maane na kyon kehnay?
Phoolon ke jaisi teri jawaani
Jaane kya jaadoo chalaye...
Mera dil tota ban jaaye,
Kaisa mithu mithu bole haye!...

(for those of you who don't know, this song is not original and was copied from a Marathi song which shares almost the same sentiment.)

Now, if seeing those lyrics doesn't remind you of the tune of that song and doesn't immediately bring up the picture of Neelam and my man Chunky Pandey dancing together in Ghat dress in some garden at Observation Post (which is a sort of park in Aarey Colony, Bombay, and is the place where most ``OUTDOOR SCENES'' in the 80s were shot, it was a time when people didn't have to rush off to Switzerland/Belgium/UK/USA/Maldives for filming song sequences for a movie which claimed to be patriotic and INDIAN), then nothing ever will.

Anyway, this movie stars Pran as the honest and God-fearing (Main sirf bhagwaan se darta hoon kamine! types) inspector and Danny Dengzongpa as Pasha (thanks, xzintax@yahoo.com), the daku (dacoit). During a confrontation, Pran chastises Danny for being bad and says that its just his bad blood and bad environment that have made Danny bad, and that Pran thinks even bad blood can be brought up to possess good character. Danny scoofs at this, and decides to prove that he's right, and exchanges Pran's newborn son with his own newborn son. And, of course, at this point, I'm sure you can see the main titles and credits of this movie start to roll. Pran brings up Danny's son with all the love in the world, while Danny teaches the tricks of his trade to Pran's son (well, actually, the main titles start to roll when this kid is being chased by the cops and they show his feet or something and he grows up to be Sunny Deol)...
Danny's son (the one growing up with Pran) grows into the great and unforgettable (COME BACK FROM BANGLADESH! WE MISS YOU!)      Chunky Pandey,  who also becomes an inspector.
And, of course, Sunny Deol, even though he is a petty thief and all that, grows up with a conscience.
So that in the final confrontation scene, Pran is forced to deliver this lengthy and really laboured piece of dialogue which basically shows Danny that he was wrong and Pran was right in the beginning of the movie, and Pran's testimony goes something like this (please try to imagine Pran delivering these dialogues with his eyes slitted to show he means business, like he always does, with every other word accentuated by a shake of his head):

``Achcha khoon agar achche mahoul mein paida ho, to woh hamesha achcha hota hai. Uski misaal main khud hoon!
Achcha khoon agar gande mahoul mein bada ho, to woh hamesha achcha hota hai. Iski misaal hai mera beta, (insert standard Munna-esque name here for Sunny Deol)!
Ganda khoon agar achche mahoul mein bada ho, to woh hamesha achcha hota hai. Iski misaal hai tumhara beta, (ditto for Chunky Pandey)!
Ganda khoon agar gande mahoul mein paida ho, to woh hamesha ganda hota hai! Iski misaal tum khud ho, (insert typical daku name for Danny)!!!...''

Man, was that laboured or was that laboured!!! And of course, true to the Hindi filmi characterization of dakus, they might be illiterate, but they will stand around and listen to such random generalizations from their nemeses instead of just blowing their heads off.... But then we are digressing. Let's tabulate this set of inputs (two inputs: Khoon and Mahoul) and the output and example in each case...
 

Khoon (Blood)	Mahoul (Environment)	Grows up to possess	Example from Paap Ki Duniya
Ganda (Bad)	Ganda	Ganda character	Danny
Ganda	Achcha (Good)	Achcha character	Chunky (YAY!!!)
Achcha	Ganda	Achcha character	Sunny
Achcha	Achcha	Achcha character	Pran

See a pattern here? Of course you do!!! It's just the OR gate... Didn't I tell you this was going to be an example! It has always been found that chlidren understand stuff better if we use examples. I guess that's exactly what Pran was trying to do in this scene, trying to teach Danny some logic. But, if you have seen the movie (you don't need to, if you know standard formula suggests what will happen anyway), you will know that Danny doesn't give a shit about Pran's gates, and therefore is sent to Hell's gates by the three greats. I think it was unfair, though that they killed off Chunky in the end. THIS IS NOT FAIR!!!! I WANT A REMATCH!!!
Thanks to Subroto for reminding me of this situation and for comparing it to logic.
Now that you have learnt some logic, want to learn some diplomacy? Want to learn to tactfully change the subject? Click here.

Note: July 23, 2001:
The above example is only to illustrate the OR gate, and it does not necessarily mean that whatever Pran claims about the blood-environment relationship is true. For example (this example comes thanks to Ajay Singh Negi), consider the movie Dharam Karam, starring Raj Kapoor, Prem Nath and Randhir Kapoor among others (I guess *you* will remember this movie because of the song, ``Ek Din Bik Jaayega'', but *I* remember this movie because of the routine that ended: ``Eh! Aur ek lakh ka char guna?'' ``Anda! (Egg)''). This movie is also about children getting exchanged. Randhir Kapoor, Raj Kapoor's son (in the movie, you numbskull!) grows up under the able guidance of Prem Nath, while Prem Nath's son grows up under Raj Kapoor's sad ``What you sow you will reap'' guidance, and in this case, Good Blood + Bad Environment is still Good, but Bad Blood + Good Environment is Bad (actually, this is true in most movies of the exchanged-children genre - the Good father always keeps wondering why his son is such an asshole, and it ends up he's not his son after all...), therefore this can't be an OR gate. It just is a nature vs. nurture assumption that Bad always begets Bad, no matter how much logic and electronics you know!