2019 Newsletter: 56/58 — PreviousNext — (Attach.)

Sydney Harbour
WEEKLY NEWSLETTER 4 - 9 NOVEMBER 2019

Hello and Welcome,

Meetings This Week:

Friday Forum - Friday Nov 8th - 9:30 am (10:00 am meeting start) - 12 noon

The usual Q&A and other discussions. Maybe a Pi demonstration too.

Communications - Friday Nov 8th - 1:00 pm - 3:00 pm

The usual Q&A and other discussions.

Meetings Next Week:

Programming - Tuesday Nov 12th - 5:30 pm (6:00 pm meeting start) - 8:00 pm
Web Design - Saturday Nov 16th - 1:30 pm (2:00 pm meeting start) - 4:00 pm

Current & Upcoming Meetings:

79 2019/11/02 - 14:00-17:00 - 02 Nov, Saturday - Penrith Group
80 2019/11/08 - 09:30-12:30 - 08 Nov, Friday - Friday Forum
81 2019/11/08 - 12:30-15:30 - 08 Nov, Friday - Communications
82 2019/11/12 - 17:30-20:30 - 12 Nov, Tuesday - Programming
83 2019/11/16 - 13:30-16:30 - 16 Nov, Saturday - Web Design
84 2019/11/19 - 09:30-12:30 - 19 Nov, Tuesday - Tuesday Forum
85 2019/11/22 - 09:30-12:30 - 22 Nov, Friday - Digital Photography
86 2019/11/26 - 17:30-20:30 - 26 Nov, Tuesday - Main Meeting

ASCCA News:


Tech News:

“NSW drivers' licences are now available on your phone”:

See the Techradar article by Stephen Lambrechts | Oct 29 2019.

But you may have some trouble signing up right now

Announced three years ago and officially put into motion back in May this year, followed by an unfortunate missed deadline in August, digital drivers' licences are now officially available in NSW — though you may have trouble accessing yours right now.

Digital licence functionality began its rollout via the Service NSW app on Android and iOS this morning. In order to access your driver's licence on your phone, you'll first need to create a MyServiceNSW account, then enter your surname, licence number and the number on the back of your physical licence.

However, many have so far experienced problems in the process of linking their licence to their MyServiceNSW account due to a high number of users clogging Service NSW's servers.

Screen message: "We're a little busy right now. Please try again."

We tried numerous times over the last few hours to link our licences, only for the Service NSW app to either hang indefinitely in the 'checking your account' phase of the setup process, or receive a "we're a little busy" message.

It's worth noting that according to the Service NSW website, "It's illegal to access your Digital Driver Licence when driving, including when stationary, unless you're asked to do so by a police officer."

The digital licence is also an acceptable form of identification for entering pubs, clubs and other 18+ venues.

Read more »

“Multi-Layer SSDs: What Are SLC, MLC, TLC, QLC, and PLC?”:

See the How-To Geek article by IAN PAUL | @ianpaul | OCTOBER 25, 2019, 6:40AM EDT.

Solid-state drives improve the performance of aging computers and turn newer PCs into speed machines. But, when you shop for one, you're bombarded with terms, like SLC, SATA III, NVMe, and M.2. What does it all mean? Let's take a look!

It's All About the Cells

Current SSDs use NAND flash storage, the building blocks of which is the memory cell. These are the base units onto which data is written in an SSD. Each memory cell accepts a certain number of bits, which are registered on the storage device as 1 or 0.

Single-Layer Cell (SLC) SSDs

The most basic type of SSD is the single-layer cell (SLC) SSD. SLCs accept one bit per memory cell. That's not a lot, but it has some advantages. First, SLCs are the fastest type of SSD. They're also more durable and less error-prone, so they're considered more reliable than other SSDs.

SLCs are popular in enterprise environments where data loss is less tolerable, and durability is key. SLCs tend to be more expensive, and they aren't typically available for consumers. For example, I found a 128 GB enterprise SLC SSD on Amazon that cost the same as a 1 TB, consumer-level SSD with TLC NAND.

If you do see a consumer SLC SSD, it probably has a different type of NAND and an SLC cache to improve performance.

Multi-Layer Cell (MLC) SSDs

The "multi-" in multi-layer cell (MLC) SSDs isn't particularly accurate. They only store two bits per cell, which isn't very "multi-," but, sometimes, technology naming schemes aren't always forward-looking.

MLCs are a bit slower than SLCs because it takes more time to write two bits onto a cell than just one. They also take a hit in durability and reliability because data is written to the NAND flash more often than with an SLC.

Nevertheless, MLCs are solid SSDs. Their capacities aren't as high as other SSD types, but you can find a 1 TB MLC SSD out there.

Triple-Layer Cell (TLC) SSDs

As its name implies, TLC SSDs write three bits to each cell. At this writing, TLCs are the most common type of SSD.

They pack more capacity than SLC and MLC drives into a smaller package, but sacrifice relative speed, reliability, and durability. That doesn't mean TLC drives are bad. In fact, they're probably your best bet right now — especially if you're hunting for a deal.

Don't let the notion of less durability get you down; TLC SSDs usually last for several years.

Terabytes Written (TBWs)

Typically, SSD durability is expressed as TBW (terabytes written). This is the number of terabytes that can be written to the drive before it fails.

The 500 GB model of the Samsung 860 Evo (a popular SSD from a few years ago) has a TBW rating of 600; the 1 TB model is 1,200 TBW. That's a whole lot of data, so a drive like this should serve you for many years.

TBWs are also "safe level" estimates; SSDs commonly exceed these limits. To be on the safe side, though, make sure you backup to minimize data loss — especially with older drives.

Read more »


Fun Facts:

“counter=$((counter+1))”:

The difference between programming languages is enormous.

Take the simple request to add 1 to a number. Some languages let you say "x = x + 1" or maybe "x++" to increment a number and "x--" to decrement it by 1.

But what language makes you say "counter=$((counter+1))" ? The answer is the Bash command language in Linux. And Bash insists on having NO BLANKS around the "=" sign! What language insists on that?

I was trying to monitor the output of a program in Linux the other day, and I thought that I'd like to see a running counter showing the number of minutes taken so far — a simple enough request.

The waiting for a minute between checks was easy: "sleep 60" was all I had to do.

But the details of incrementing the counter was something that I'd forgotten. Google to the rescue, of course. But how to display it on the same line each time, so the display doesn't just scroll off the top of the screen? Surely I could use something like "echo Msg-counter\r" where "\r"means carriage return, without the linefeed.

No, that was difficult, too! I finally had to use 'printf "$counter mins...\r"' (echo wasn't reliable).

I also wanted the "system bell" to sound when the program found the final result.

Nothing as easy as "echo BELL". Oh no! We had to use "play -n synth .5 sin 900" which means use 900 Hz in a sinusoidal sound wave for .5 seconds! A striking tone — much better than a beep on the old system buzzer.

Anyway, the program runs properly and now tells me when it finds the result. I am amazed.

Ed.

“NOT -1/12 but -1/8 !”:

You've probably all heard the claim that the sum of all the positive integers is -1/12. Well, there are videos all around YouTube to prove it, so see if you agree with them.

Here's a 7:49 minute YouTube video from respected Channel, Numberphile and another 8:51 minute one from superstar maths teacher, Eddie Woo. If these two sources say it's true, there must be something in it.

Unfortunately, they both start with the infinite sum S = 1 - 1 + 1 - 1 + 1 - 1 + ... and claim that it is equal to 1/2. Taking partial sums (stopping at 1 term, then stopping at 2 and so on) gives 1 or 0, but NEVER 1/2.

We won't be pushing any such bogus mathematics on anyone here.

We'll just use ordinary arithmetic and a little algebra.

Let T = 1 + 2 + 3 + 4 + 5 + 6 + ... be the total we are looking for.

Then group the terms as follows:

T = 1 + 2 + (3 + 4 + 5 + 6 + 7) + (8 + 9 + 10 + 11 + 12) + ... where the brackets contain groups of five consecutive numbers centred at a multiple of 5. In other words, T = 3 + 25 + 50 + 75 + 100 + ...

But we see a pattern here: T = 3 + 25 x (1 + 2 + 3 + 4 + ... ) = 3 + 25T.

Subtracting T from both sides gives 0 = 3 + 24T or T = -3/24 or -1/8.

It works if you group any odd number of terms centred on a multiple of that odd number too.

The simplest example would be T = 1 + (2 + 3 + 4) + (5 + 6 + 7) + (8 + 9 + 10) + ... which gives the equation T = 1 + 9T or 8T = -1 or T = -1/8.

No funny infinite sums that add up to 1/2.

Hmmm, interesting ...

Ed.


Bob Backstrom
~ Newsletter Editor ~

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