# Why do many workplace PCs still run on old software?

A few reasons:

1.  Cost. Upgrading software is expensive.  If an upgraded licence costs \$50 that may not seem like much, but doing that for 5,000 machines gets really expensive really quickly.

2.  Compatibility. Very often, companies will have custom or specialized software that may not function well with newer software.  If the older software doesn’t have patches/upgrades, or those patches/upgrades are not cost effective (see point 1) you may need to keep other software downgraded in order to preserve compatibility.

3.  Security/Reliabilty. Older software – particularly in the enterprise – can be more secure and/or stable because the bugs and security holes have been patched. Newer software may introduce newer bugs that can compromise operations.

4. Usability. Not everyone is computer literate in a company and upgrading their software may confuse them to the point where they struggle to do their job until they learn the new software.

# How are hexadecimal color codes formed?

One of the ways computers store color information is Red, Green, Blue (RGB) format. What the computer does is it stores a value from 0 – 255 for each of those three colors. Some examples:

0,0,0 = Black

255,255,255 = White

255,0,0 = Pure Red

0,255,0 = Pure Green

0,0,255 = Pure Blue

And all the various combinations of colors in between. As we know, computers operate in 1’s and 0’s. Bits and bytes. In memory and on disk, it isn’t storing numbers from 0 to 255, it’s storing a single byte, from 00000000 to 11111111.

Writing out all the bits of a byte can be cumbersome, so hexadecimal is often used, because you can represent four bits with a single hex character, or 2 hex characters to represent a single byte. To show the difference, take a look at some of our previous examples in binary and hex:

Black = 00000000,00000000,00000000 or 0x000000

White = 11111111,11111111,11111111 or 0xFFFFFF

Red = 11111111,00000000,00000000 or 0xFF0000

Much more compact and simpler and easy for computers to read and interpret.

In short, when you see a hex color code, the first two characters represent the amount of red, the second two represent the amount of green, and last two represent the amount of blue.

# How can any storage device keep information once unplugged from the computer/power?

Imagine a board with four switches. And each switch has either on or off position.

Imagine there’s a bulb connected to each switch. So let’s say you have the switches in on, on, off, on position. Logically the second to last bulb is off while the rest is on.

Now disconnect the board from your circuit. Did the switches go back to some default position? No, because there isn’t any. They’re still in their last set on/off position.

So now you can store the board in your drawer for years and it will still hold the information. On, on, off, on.

Connect it to the bulbs again and you will see what you saw years ago, Bulbs 1, 2 and 4 are on while the 3rd one is off.

So the board was able to hold four bits of information for years without any power source.

# Why do lithium-ion batteries lose their ability to maintain charge after many cycles of charging?

It is due to several things.

The most important is physical. During charging/discharging lithium atoms move from one electrode to the other. The lithium goes into tiny pores in a sponge like electrode, but when this happens the sponge swells up. Repeated swelling and shrinking eventually causes cracking and fractures in the electrode, degrading it.

The other main effect is chemical reaction in the electrolyte. During charging, tiny amounts of electrolyte material undergo unwanted chemical reactions with the electrode chemicals. Eventually the electrolyte gets polluted with all the byproducts of these reactions degrading it.

# Why do lines appear in the picture when we photograph a computer screen?

Screens do not generate an entire image at once. Rather, each row of pixels is rendered one at a time until the entire image is rendered. Imagine the screen as filling in a color by numbers from left to right one line at a time.

This happens a number of times per second based on your framerate. A 59.99 hertz screen does this nearly 60 times per second. If your screen has 4000 pixels, it does one pixel every .015 seconds.

Similarly, most digital cameras use what’s known as a rolling shutter. They don’t capture the whole image at once, but instead one line at a time. This is similar to how a photocopier works.

When the rolling shutter is out of time with the framerate of a screen, it catches different cycles of rendering in the same still.

Imagine if you could instantly swap out a series of photos while a photocopier tried to scan them. You’d end up with a similar effect.

# How does a computer unset a bit (set it from 1 to 0) in memory/storage?

It depends on the particular kind of storage.

In magnetic storage, like a spinning-disk hard drive, it magnetizes the region storing the bit in the opposite direction.  (In practice, hard drives write entire blocks at a time, but the technology could theoretically be managed a bit at a time.)

In typical flash storage, like in solid-state drives or external flash drives, it can’t write a single bit at a time. In order to change a bit from a 1 to a 0, it erases an entire block of memory, then rewrites the new data into it.

In DRAM, which is the typical kind of RAM in a computer, it connects the capacitor holding the bit to a current drain, which allows it to discharge.  (Similarly to others, standard DRAM actually can only write a whole line at a time, so switching a single bit means writing the previous value into all the other bits.)

In SRAM, which is typically used for things like on-CPU caches, the bit line is set to 0 and then the write line is set to 1.  The transistors switch into the alternative configuration, and then the write line is set back to 0, which causes them to maintain their current configuration until written again.

# How do motion detectors detect motion in the dark?

There are two common types of motion sensors – passive infrared (PIR) and Ultrasonic. The most common type is PIR which sees IR which is emitted by hot objects. There is a special lens in front of the sensor so a warm object moving through its field of view creates sudden transitions that are easy to detect. Since it is relying on heat emissions it works fine with or without light.

Ultrasonics send out a sonar burst and effectively echo locate like a bat. They check the sound they get back after each one and compare it to the last one, if it changed significantly then something in the space moved and they trigger.

# How do baggage scanners at the airport work? What do the different colors on the x-ray mean?

The x-ray devices in luggage scanners are a bit more complicated than the x-ray medical imaging devices. In particular, they’re set up to identify and distinguish between different kinds of objects, whereas medical x-rays are pretty much only interested in one: bones.

The trick is that not all x-rays are created equal. The x-ray source will send out x-rays in a range of energy levels. Organic objects block some low-energy x-rays, but not higher-energy x-rays. Plastics block low-energy x-rays better than organic objects, but not as effectively as metal objects, which pretty much block everything.

The device is set up so that the x-rays pass through your luggage and then hit the first detector, which sends an image to the computer. But the x-rays then pass through a filter that blocks out all low-energy x-rays before hitting a second detector. That sends another image to the computer, this time only showing those objects that block high-energy x-rays. By combining these two images, the software can distinguish between organics, inorganics (e.g., plastics), and metals. It then assigns different colors to each.

Most manufacturers use black for metal and orange for organics, but it could vary from machine to machine.

# What is the difference between noise isolating and noise cancelling headphones?

Noise Isolating

Consider the earphones that have earbuds in them. They block outside noise by providing a noise reducing barrier.

Noise Cancelling

Headphones that essentially listen to ambient noise and produce an opposite sound wave to blank out the unwanted sound. Fill your bathtub with water. Drop two rocks into the tub one at each end.  When the waves collide you will see a spot where the water seems calm because the waves are cancelling each other out. Noise cancelling headphones produce this negative wave by listening in to the outside noise and producing the opposite wave to cancel out the wave just like in the water.

# How is it possible for ISP’s to know we are doing online? Isn’t HTTPS supposed encrypt content so it can’t be read?

The ISP (Internet Service Provider) is your mailman. They need to get packages to where they need to go. HereBeAnswers, for example, is sending you a package containing this answer. You pay the mailman monthly for a rate at which they send packages from you and to you.

HTTPS encrypts the package’s contents, however the ISP’s responsibility is still to move the package from A to B, and therefore needs to know what these A and B are. Therefore the postage address cannot be encrypted, and your ISP can track who you are exchanging packages with, be it HBA or YouTube or Netflix.

So your ISP can’t actually see what you are viewing on HBA, YouTube, or Netflix, but they can see which sites you are accessing.