Mirror Magazine

Mirror Magazine

Computer trivia

Enhance your computer literacy
Dynamic DNS - Short for dynamic Domain Name System, a method of keeping a domain name linked to a changing IP address, as not all computers use static IP addresses. Typically, when a user connects to the Internet, the user's ISP assigns an unused IP address from a pool of IP addresses, and this address is used only for the duration of that specific connection (this is what happens most of the time when you log on with a dial-up modem). This method of dynamically assigning addresses extends the usable pool of available IP addresses. A dynamic DNS service provider (SLT is one example) uses a special program that runs on the user's computer, contacting the DNS service each time the IP address provided by the ISP changes and subsequently updating the DNS database to reflect the change in IP address. In this way, even though a domain name's IP address will change often, other users do not have to know the changed IP address in order to connect with the other computer.

GUID - Short for Globally Unique Identifier, a unique 128-bit number that is produced by the Windows OS or by some Windows applications to identify a particular component, application, file, database entry, and/or user. For instance, a Web site may generate a GUID and assign it to a user's browser to record and track the session. Windows also identifies user accounts by a user name (computer/domain and user name) and assigns it a GUID. Some database administrators will even use GUIDs as primary key values in databases. GUIDs can be created in a number of ways, but usually they are a combination of a few unique settings based on a specific point in time (e.g., an IP address, network MAC address, clock date/time, etc.).

Static electricity and computers… Beware!
In the past few months I had to carry my hard drive around quite a bit… To get it formatted, expand my MP3 collection (which has taken up almost three-quarters of my disk) and to complete a multimedia presentation were a few reasons why I had to do so. But I was terrified to find out later that, whenever the casing of a computer is opened and its internal workings are exposed (to change a hard drive or add memory; for example), there is a danger of damaging the computer with the buildup of static electricity that is held by the human body. The internal workings of a computer, and especially the hard drive, are extremely susceptible to static electricity, which can cause considerable damage to the hard drive if it is zapped with even a small amount.

Microchip damage can occur if it is exposed to static electricity as low as 500 volts, and humans are not able to perceive static electricity until it has reached about 1,500 volts. (Walking across a rug can produce a static electricity voltage of up to 12,000 volts, but static voltage is not life threatening.) So it is possible to damage a hard drive with static electricity that is not even felt by the person because it is at such a low voltage.

Static electricity is caused by a process called triboelec-trification (I did not come up with this word). Everything around us, and including us, is made of atoms, and every atom has at its centre (nucleus) positively charged protons and neutrons, which have no electrical charge. Surrounding the atom are negatively charged electrons. The protons and neutrons in an atom do not change, but the electrons can move from one atom to another. When two objects touch, they exchange electrons; which causes one object to become electrically positive and the other to become electrically negative. When an object touches another object with either an opposite or neutral charge, electrons flow. Static electricity is created when electrons move back and forth between atoms.

To avoid zapping your components with static electricity, take precautions to ground the static electricity before touching any of the internal components of the computer. Wearing an ESD wrist strap will prevent any static electricity from damaging your computer. Another way to ground the static electricity is to touch the internal metal frame of the computer's case while the computer is plugged into an electrical socket (keep it switched off though… don't say I didn't tell you!). The static electricity will be discharged and grounded as the electrical circuit is grounded via the AC outlet. And to be on the safe side, always handle the electronic circuitry on the motherboard, video card, modem, sound card, hard drive and other internal components by any insulated, non-circuitry areas - if they have them - to ensure that you do not send a bolt of static electricity coursing through it!

Are deleted files completely erased?
A common misconception when deleting files is that they are completely removed from the hard drive. However, highly sensitive data can still be retrieved from a hard drive even after the files have been deleted, because the data is not really lost. Files that are moved to the recycle bin (on PCs) or the trash can (on Macs) stay in those folders until the user empties the recycle bin or trash can. Once they have been deleted from those folders, they are still located in the hard drive and can be retrieved with the right software (e.g. Norton Utilities).

Any time a file is deleted from a hard drive, it is not erased. What is erased is the bit of information that points to the location of the file on the hard drive. The operating system uses these pointers to build the directory tree structure (the file allocation table), which consists of the pointers for every other file on the hard drive. When the pointer is erased, the file essentially becomes invisible to the operating system. The file still exists; the operating system just doesn't know how to find it. It is, however, relatively easy to retrieve deleted files.

The only way to completely erase a file with no trace is to overwrite the data. The operating system will eventually overwrite files that have no pointers in the directory tree structure, so the longer an unpointed file remains on the hard drive the greater the probability that it has been overwritten. There are also many "file erasing" software products currently on the market that will automatically, permanently erase files by overwriting them.

Northern vs. Southern hemisphere monitors
Did you know that the monitor you are using with your computer may be affected by which hemisphere of the earth you are in? The Northern and Southern hemispheres of the earth have different magnetic fields, each pulling toward its respective pole. Monitors with cathode ray tubes, which form the majority of desktop monitors in use today, are manufactured specifically for the hemisphere they are going to be used in. CRT monitors work by moving electron beams back and forth behind the screen, and the earth's magnetic fields act on the electron beams, pulling them toward the field. A monitor calibrated for the Northern hemisphere can still be used in the Southern hemisphere, but the colours and the image would be slightly affected. Most major monitor manufacturers give users the controls to manually adjust the image. But LCD monitors are not affected by this phenomenon.

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