Name: 七段式顯示器最長的字是什麼？ (What's The Longest Word You Can Write With Seven-Segment Displays?)
Uploaded: 2021-01-14T10:36:36.000Z
Duration: 8 min 56 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

We don't see them as much in electronics these days

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because screens are a lot cheaper than they used to be, but these used to be everywhere

from clocks to supermarket checkouts to calculators to slot machines.

Here, they're being used as part of the Megaprocessor at the Centre for Computing History in Cambridge.

This is the clock speed that the whole system is running at.

Seven-segment displays are a really clever bit of design.

Seven is the minimum number of segments required to show every number using straight lines.

It doesn't matter that the 4 isn't actually how most people write a number 4,

it's close enough that we've all just got used to it.

means that there are eight lights here to turn on or off, which is convenient:

so you can store the state of those lights in just one byte of memory.

And you can use these for some letters, too.

You could show the word "Error", or even base-16 numbers.

But there's no way you can write an M or a W on this display.

what is the longest English word that you can write on a seven-segment display?

I love questions like this because there are so many ways to approach them.

I'm going to give one solution here because that's the way I want to tell the story,

but I can think of a couple of others just off the top of my head,

and there will be a dozen more that I haven't thought of,

and fortunately here the work has been done for us.

There is a public-domain list of English words available,

right at the top there are two different spellings of 'aarrgh'

and I'm really not sure either of those should count,

but the list is good enough for our purposes.

We can manually filter it later if there are any strange results.

Now, I'm going to code this in JavaScript using Node.

Not the best language, but it's not bad for beginners,

and importantly it's easy for me to explain.

First, we're going to add a bit of boilerplate code,

I Googled 'load array from file in node' and I adapted some of the results.

This is how basically how everyone codes stuff like that.

Don't ever be afraid that you're not a real programmer because you still look stuff up.

The important part about programming is not remembering exact words or syntax:

it is breaking down a problem, working out how to solve it,

and then fixing all the inevitable bugs in your solution.

It's about holding lots of complicated connections in your head,

not the exact magic words that you need this one time.

I still forget which order to put basic stuff in sometimes.

Anyway, the first line loads in the bits of Node that deal with reading and writing files,

and the next line loads the entire dictionary into a single long string called "words".

The next line converts that single string into an array, a long list of smaller strings,

based on where the new-line characters are.

And now we have an array of all the words in the English language:

Let's see how long that array is by telling the console to output the array's length.

Okay, more than 370,000 words, each one in a separate item in that array called “words”.

Next problem: we need to filter that list

and remove any words that use letters that we can't display with seven segments.

Which gives us an interesting design problem:

Now, I'm going to use fancy graphics here rather than actual seven-segment displays,

you can try and figure out the After Effects expressions that I used to make these.

Letters A through F are easy, there's almost a standard for those.

We can't use the obvious pattern, because that's a 6, or a 9 if it's lowercase.

And if we use an alternate pattern for it, it's... not really a G?

But to be fair, if any of those patterns appear at the start of a word like 'GOAL',

no-one's going to look at it and say 'oh, six-OAL'.

But I'm going to make the call that we don't allow it.

it's not like the half-assed G which sorta looked kinda like a C?

It's clear. I mean, I don't care that I'm not applying strict rules here,

I'm just going on what feels right, and if you disagree,

Other letters that I'm ruling out: K. Just can't be done, requires a diagonal.

M: I've seen it displayed like this before, but: no. Not having it.

N is borderline, but I'm going to allow it because there's nothing else it could be.

And as for Z... no. It needs the diagonals. Not having it.

Here's our alphabet, then. Eighteen letters left, eight disallowed.

That's actually more than I'd expected left in there.

And I'm going to cheat. I know this is called the Basics,

but doing this the long way would be really dull,

so I'm going to put those disallowed letters into something called a regular expression,

Those slashes indicate that it's a regex,

and whatever's inside those slashes is like a test that a string can match against.

So this regex would match any word with an X in it,

whether that X is at the start or middle or end.

As long as there's an X somewhere in the string, it passes that test.

then surround them with square brackets so they're treated as a class,