# Remember These



## pg tips (May 16, 2003)

The loft clearout continues! Look what I found.

Laptops have certainly progressed thank god!


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## Mrcrowley (Apr 23, 2003)

Ooooerrrrrr


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## ron (Dec 12, 2003)

I like it









Talking of finding things - a week or so ago I found an original Sinclair C5 sales brochure!

For those who don't know what a C5 is - click the link below

If you want a real laugh - click on the Modifications link!























http://www.sinclair-research.co.uk/c5/index.php

In good condition these will fetch about Â£1,500 (compared to the original price of about Â£480, from memory)


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## rhaythorne (Jan 12, 2004)

Cool PG!









Does it work? Is it a 286?


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## Roy (Feb 23, 2003)

I had one of those.


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## ron (Dec 12, 2003)

Roy said:


> I had one of those.


 A C5 or a PG 'laptop'?


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## pauluspaolo (Feb 24, 2003)

I found this in my loft a couple of months ago









It's an early HP calculator (HP35), I was going to try and sell it as I'd seen one like it go for about Â£200 on Ebay. This one was rescued from work during a throw out of defunct equipment - it has red led numbers (like the Sinclair watch) and works perfectly. It's complete with a decent carry case, full instructions and 240v power supply (no battery though).


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## Roy (Feb 23, 2003)

ron said:


> Roy said:
> 
> 
> > I had one of those.
> ...


 The Amstrad 512 K laptop, no hard drive just one 720k floppy.

Those were the days


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## pg tips (May 16, 2003)

Rich it's an Amstrad PPC (portable PC if your built like Arnie







) 512, as Roy says 512K no hard drive, mine has two floppy drives. They did a 640 version as well. You can run it on batteries I think it took 10 C cells and they lasted about 15 minutes! This is actually my dad's so I'll ask him if he wants it back, if not it's going on ebay!


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## Stan (Aug 7, 2003)

Still fancy an Amstrad NC 100 or 200, simple mobile computing.


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## pg tips (May 16, 2003)

a number of 100's on ebay stan but also a 200!

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...ssPageName=WDVW

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...ssPageName=WDVW


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## Stan (Aug 7, 2003)

Ta PG,









Might put a bid in but I now need a new printer. Bugger.









I must get some money for watches at sometime, this is just not fair.


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## pg tips (May 16, 2003)

I had one of these but I can't find it now!







I'm sure I didn't throw it out.


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## rhaythorne (Jan 12, 2004)

That looks familiar! I had this one


















Pinched the picture from the Vintage Calculators Web Museum


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## pg tips (May 16, 2003)

the one I had was programmable, could do all sorts but the problem was the instruction book was an inch thick! Our physics teacher got a load of them and floged them off to the students. I didn't realise there was a calculator museum!


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## ron (Dec 12, 2003)

rhaythorne said:


> That looks familiar! I had this one


For anyone that still has one, try dividing 0 by 0

It starts doing an incremental count on the screen - ie 1 > 2 > 3 etc









Excellent

Mind you - I've always wondered if 0/0 was:

a ) 1

b ) 0

c ) infinity

I was always taught that something divided by 0 was 'infinity' - so it's c)

But if you divide the same number by itself, logic says it's 1, ie answer a)

Or is it c)?

My head hurts now
















If there are any mathematicians on forum - please answer, as I have wondered about this before


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## pg tips (May 16, 2003)

The short answer Ron is you cannot divide by zero.

this might help or not









Brahmagupta attempted to give the rules for arithmetic involving zero and negative numbers in the seventh century. He explained that given a number then if you subtract it from itself you obtain zero. He gave the following rules for addition which involve zero:-

The sum of zero and a negative number is negative, the sum of a positive number and zero is positive, the sum of zero and zero is zero.

Subtraction is a little harder:-

A negative number subtracted from zero is positive, a positive number subtracted from zero is negative, zero subtracted from a negative number is negative, zero subtracted from a positive number is positive, zero subtracted from zero is zero.

Brahmagupta then says that any number when multiplied by zero is zero but struggles when it comes to division:-

Positive or negative numbers when divided by zero is a fraction the zero as denominator. Zero divided by negative or positive numbers is either zero or is expressed as a fraction with zero as numerator and the finite quantity as denominator. Zero divided by zero is zero.

Really Brahmagupta is saying very little when he suggests that n divided by zero is n/0. Clearly he is struggling here. He is certainly wrong when he then claims that zero divided by zero is zero. However it is a brilliant attempt from the first person that we know to try to extend arithmetic to negative numbers and zero.

In 830, around 200 years after Brahmagupta wrote his masterpiece, Mahavira wrote Ganita Sara Samgraha which was designed as an updating of Brahmagupta's book. He correctly states that:-

... a number multiplied by zero is zero, and a number remains the same when zero is subtracted from it.

However his attempts to improve on Brahmagupta's statements on dividing by zero seem to lead him into error. He writes:-

A number remains unchanged when divided by zero.

Since this is clearly incorrect my use of the words "seem to lead him into error" might be seen as confusing. The reason for this phrase is that some commentators on Mahavira have tried to find excuses for his incorrect statement.

Bhaskara wrote over 500 years after Brahmagupta. Despite the passage of time he is still struggling to explain division by zero. He writes:-

A quantity divided by zero becomes a fraction the denominator of which is zero. This fraction is termed an infinite quantity. In this quantity consisting of that which has zero for its divisor, there is no alteration, though many may be inserted or extracted; as no change takes place in the infinite and immutable God when worlds are created or destroyed, though numerous orders of beings are absorbed or put forth.

So Bhaskara tried to solve the problem by writing n/0 = infinity . At first sight we might be tempted to believe that Bhaskara has it correct, but of course he does not. If this were true then 0 times infinity must be equal to every number n, so all numbers are equal. The Indian mathematicians could not bring themselves to the point of admitting that one could not divide by zero. Bhaskara did correctly state other properties of zero, however, such as 0 squared = 0, and 0 = 0.

From HERE


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## Nalu (Nov 28, 2003)

pg tips said:


> this might help or not


Not. My head hurts.


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## adrian (May 23, 2004)

Huh?


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## Nin (Jul 16, 2004)

Ha!

When I divide 0 by 0, my Psion says "Maths error". That's why I like Psions - they go the extra mile. My Casio calculator just says "Err". But it pretty much describes my whole experience with numbers really.

But then, is 0 a number?

Nin


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## pg tips (May 16, 2003)

0 is nothing, zero, zilch, nowt, naught, but without it we'd be stuffed, odd really when you think about it, now my head hurts!


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## Nin (Jul 16, 2004)

There's got to be a gag there about getting something for nothing.


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## ron (Dec 12, 2003)

pg tips said:


> this might help or not


PG - many thaks for posting that









I understood about 70-80% of it. I actually did A Level Maths (got a 'D' in the end







) - I remember then (vaguely) concepts like you can actually have square roots of negative numbers(!). But let's not go there









thanks


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## pg tips (May 16, 2003)

I did a year of A level pure maths' applied maths and physics. Then I had enough left home and joined the RAF. Looking back now and at todays standards of A levels I probably would pass a current A level with a bit of a refresher.

My brother in law is a math geek, just become a fully qualified insurance actuary at the age of 26! Probably one of the youngest in the country. His maths skills just leave me dumbfounded. divides numbers bigger than 1 million by ones bigger tha one thousand in his head for fun!







He's a wizz on countdown as well!


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## Griff (Feb 23, 2003)

I used one of these!!!


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## traveller (Feb 27, 2003)

I still use one of these.


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## Griff (Feb 23, 2003)

EEEEErrrmmm hardly..................but occasionally one of these


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