Depends on the chip. Some read -5V as 0 and +5V as 1. Some are tri-state using -5V, 0, and +5V. It's actually voltage and not current that it is using. At least the chips I worked with years ago were that way.
[Edit] And yes, some chips used 0V as 0 and +5 as 1. [/Edit]
There are only 10 types of people in the world, those who understand binary and those who don't.
in many case three state of currency doesn't mean three state of logic.
The -5 / 0 / +5 differentiation is used just for electrical reason.
If use 0 / +5 you can have a sort of eco in the signal wich transform it self into noise.
With negative voltage there is a resorption of this eco but the chipset will not see the zero.
Practically is -5 for false and +5 for true
Yeah, it's technically possible, but indeterminate boolean values make my skin crawl. They aren't even boolean, really.
Keith Barrow wrote:
You've probably already used this without realising, nullable bit fields in SQL work along ternary logic lines.
And this is exactly why I hate them. You can have nullable bit fields, but you can also hit the server with a hammer, that doesn't make it a good idea. I'm sure there are some cases out there where this is useful, but I've only found it to be problematic. Every time I find nullable bit fields in a database, it's an issue that needs fixing rather than some clever use of three-state logic. If you need more than two values, why even use a bit field for that? Integers will do fine, and you won't have to deal with nulls.
Keith Barrow wrote:
In formal logic there is also ternary logic, in one scheme:
0: Unknown/ Indeterminate
Yeah, but in general classical logics don't allow indeterminate values. True, false, or GTFO.
Well, I'm still fuzzy on all of it, but from what I gather that's what it's intended to represent. But it still has to be stored somehow, the third state is a "indeterminate" flag to say it could be anything. But, it's still three states stored in the system.
GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)
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