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Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35

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Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35

#31

Post by wtallis »

WalterBright wrote: post #30
joezydeco wrote: post #3

Earlier quoted context omitted.

I wouldn't call them "fits", really. 40 years ago these calculators were looked upon with a bit of skepticism. Engineers that were used to seeing the log tables with their own eyes and hand-manipulating slide rules were being asked to trust the results coming out of these calculators. And lives depended on it, really. If you were a civil engineer designing a bridge and you needed to be absolutely sure the numbers you…

Trusting the numbers coming out of a calculator was ALWAYS a bad idea, especially if lives depended on it. It wasn't just the calculator making a mistake - you could have made a mistake keying in the numbers. This is dealt with by: 1. running the results through the inverse equations to verify that you get the inputs back again 2. calculating the results using an independent method to verify them 3. having a differen…

These days, we can also have our calculators keep track of the units associated with a quantity, which helps greatly with sanity-checking. If the units come out wrong or mis-match anywhere in the calculation, you'll know immediately.

Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35

#32

Post by kryptiskt »

6ren wrote: post #20

Unfortunately, as calculator prices collapsed, so did Sinclair Radionics' profits, and the company was broken up in 1979 after heavy losses. He fought Moore's law, and the law won. But this whole thing reminds me of Woz's work in the first Apples. Why wasn't his genius work similarly wiped out? Soon after the Apple, there were dozens - hundreds - of new personal computer manufacturers. I think it's software. The valu…

One unnamed reason for Sinclair Radionics' falling apart was their digital watch, Black Watch, which was the ultimate example of Sinclair's infamous cost cutting and lack of quality control. http://www.nvg.ntnu.no/sinclair/other/blackwatch.htm

Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35

#33

Post by [deleted] »

ck2 wrote: post #22
6ren wrote: post #20

Unfortunately, as calculator prices collapsed, so did Sinclair Radionics' profits, and the company was broken up in 1979 after heavy losses. He fought Moore's law, and the law won. But this whole thing reminds me of Woz's work in the first Apples. Why wasn't his genius work similarly wiped out? Soon after the Apple, there were dozens - hundreds - of new personal computer manufacturers. I think it's software. The valu…

Apple fell to the PC because the hardware was a fraction of the price since clones were allowed to exist in the PC world. Apple sued their clones out of existence. Might all be using Apple today if they had not. Then they eventually switched to pc hardware themselves.

[deleted]

Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35

#34

Post by pavel_lishin »

nealabq wrote: post #15
rarw wrote: post #10

Reverse Polish Notation - sounds like the punch line to a really bad math joke

After I got used to RPN (I had a lovely old HP-21) I found it much more intuitive. Stack-based thinking. No parentheses! (And I've used LISP for years, but that's entirely different.) RPN vs Infix/Algebraic used to be a holy-war topic. Like emacs vs vi, or iPhone vs Android. Once you go RPN, you can never go back again.

I learned it for some scholastic competition once. You're right, after the initial confusion, it was fast and intuitive.

I've forgotten it all now, of course. How often do I need to calculate something?

Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35

#35

Post by TheLoneWolfling »

nealabq wrote: post #15
rarw wrote: post #10

Reverse Polish Notation - sounds like the punch line to a really bad math joke

After I got used to RPN (I had a lovely old HP-21) I found it much more intuitive. Stack-based thinking. No parentheses! (And I've used LISP for years, but that's entirely different.) RPN vs Infix/Algebraic used to be a holy-war topic. Like emacs vs vi, or iPhone vs Android. Once you go RPN, you can never go back again.

The one issue I've already had with RPN is that you require a separator between numbers anyways - in RPN it's too easy to parse "23 4 +" as "2 34 +", for example, especially if you're writing quickly.

Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35

#37

Post by WalterBright »

wtallis wrote: post #31
WalterBright wrote: post #30

Earlier quoted context omitted.

Trusting the numbers coming out of a calculator was ALWAYS a bad idea, especially if lives depended on it. It wasn't just the calculator making a mistake - you could have made a mistake keying in the numbers. This is dealt with by: 1. running the results through the inverse equations to verify that you get the inputs back again 2. calculating the results using an independent method to verify them 3. having a differen…

These days, we can also have our calculators keep track of the units associated with a quantity, which helps greatly with sanity-checking. If the units come out wrong or mis-match anywhere in the calculation, you'll know immediately.

It's nice to have extra checks, but that changes nothing about what I said. If you are making designs that lives depend on, it is not HP's responsibility, it is YOURS and you should be using the techniques I outlined.

I'm sorry to be so blunt about this, but I feel strongly about it. I too often run into engineers that either argue that they can design a perfect system that is not subject to human error, or they try to shift responsibility onto other people or organizations.

Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35

#38

Post by WalterBright »

WalterBright wrote: post #30
joezydeco wrote: post #3

Earlier quoted context omitted.

I wouldn't call them "fits", really. 40 years ago these calculators were looked upon with a bit of skepticism. Engineers that were used to seeing the log tables with their own eyes and hand-manipulating slide rules were being asked to trust the results coming out of these calculators. And lives depended on it, really. If you were a civil engineer designing a bridge and you needed to be absolutely sure the numbers you…

Trusting the numbers coming out of a calculator was ALWAYS a bad idea, especially if lives depended on it. It wasn't just the calculator making a mistake - you could have made a mistake keying in the numbers. This is dealt with by: 1. running the results through the inverse equations to verify that you get the inputs back again 2. calculating the results using an independent method to verify them 3. having a differen…

BTW, I think every engineer should watch the series on the Smithsonian channel "Air Disasters". Each episode chronicles a particular disaster, and then painstakingly goes through what went wrong and how the problems were fixed. One can learn a lot about systems design from these case studies on how and why things go wrong.

Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35

#39

Post by [deleted] »

nealabq wrote: post #15
rarw wrote: post #10

Reverse Polish Notation - sounds like the punch line to a really bad math joke

After I got used to RPN (I had a lovely old HP-21) I found it much more intuitive. Stack-based thinking. No parentheses! (And I've used LISP for years, but that's entirely different.) RPN vs Infix/Algebraic used to be a holy-war topic. Like emacs vs vi, or iPhone vs Android. Once you go RPN, you can never go back again.

[deleted]

Re: Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35

#40

Post by nogoodnik »

lutusp wrote: post #27
WalterBright wrote: post #25

Earlier quoted context omitted.

VisiCalc on the Apple had a huge contribution to its success. It was the proverbial "killer app" that drove Apple II sales.

Yes, that and Apple Writer. Full disclosure: I wrote Apple Writer.

Thank you for writing Apple Writer.

1. I wrote most of my high school reports on it.

2. I once wrote a set of WPL programs to automate the generation of multiple-choice tests, and sold it for $50 to my uncle who was a physics teacher.

3. Apple Writer was the second program I disassembled from beginning to end (the first was Locksmith Fast Disk Copy), learning a lot in the process.

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