صدقة جارية


إليكم #تطبيق #اذكار المسلم الجديد!.. أنصحكم بتحميله! انشر الرسالة أو اعمل #ريتويت ليصبح صدقة جارية خاصة بك!

يقول الله تعالى في كتابه الكريم: ((والذاكرين الله كثيرا والذاكرات أعد الله لهم مغفرةً وأجراً عظيماً))

رطب لسانك بذكر الله مع هذا البرنامج والذي من خلاله ستقضي تجربة ايمانية رائعة لا مثيل لها!

هذا البرنامج يقوم بإظهار الأذكار والأدعية على شاشة هاتفك أثناء تصفحك للهاتف، دون الحاجة للدخول إليه حتى!

البرنامج مميز للغاية وتمّت برمجته ليعمل بذكاء! كي لا تنسى أبداً ذكر الله! 🙂

* ملاحظة: عبر نشر هذه الرسالة فإنك تحوّل البرنامج إلى (صدقة جارية) خاصة بك! حيث من الممكن أن يتناقله آلاف الناس وبذلك تكسب أجر الذاكرين والمستخدمين للبرنامج من بعدك

https://play.google.com/store/apps/details?id=com.revanen.athkar

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How Does A Hard Drive Work?


Hard disk dissection

The average laptop in the shops for around $500 has somewhere in the region of 60GB of storage memory. You see that figure and think ‘wow ““ imagine all the movies, songs, images, files and documents I could save on that baby’, right?

But did you ever think about how it actually gets stored?

If you were to stack the equivalent capacity of CDs in front of you it would surely rise to eye-level. You can fit everything on those CDs onto that hard drive. Truly amazing for an invention that has its origins in the 1950′s and was first developed as a humble cassette tape.

 

How Does a Hard Drive Work – The Basics

hard-drive-parts

In order to fully understand a hard drive you have to know how one works physically. Basically, there are discs, one on top of the other spaced a few millimetres apart. These discs are called platters. Polished to a high mirror shine and incredibly smooth they can hold vast amounts of data.

Next we have the arm. This writes and reads data onto the disc. It stretches out over the platter and moves over it from centre to edge reading and writing data to the platter through its tiny heads which hover just over the platter. The arm, on the average domestic drives can oscillate around 50 times per second. On many high-spec machines and those used for complex calculations this figure can rise into the thousands.

Hard drives use magnetism to store information just like on old cassette tapes. For that reason, copper heads are used as they are easy to magnetise and demagnetise using electricity.

Storage and Operation

Hard-Drive-sections

When you save a file, the “˜write’ head on the arm writes the data onto the platter as it spins at high RPM often in the region of 4,000. However, it doesn’t just go anywhere as the computer must be able to locate the file later. It also must not interfere or indeed delete any other information already on the drive.

For this reason, platters are separated into different sectors and tracks. The tracks are the long circular divisions highlighted here in yellow. They are like “˜tracks’ on music records. Then we have the different sectors which are small sections of tracks. There are thousands of these from centre to edge of the platter. One is highlighted blue in the picture.

In Operation

When you open a file, program or really anything on your PC, the hard drive must find it. So let’s say that you open an image. The CPU will tell the hard drive what you’re looking for. The hard drive will spin extremely fast and it will find the image in a nano-second. It will then “˜read’ the image and send it to the CPU. The time it takes to do this is called the “˜read time’. Then the CPU takes over and sends the image on its way to your screen.

Let’s say you edited the image. Well now those changes must be saved. When you click “˜Save‘, all of that information is shot to the CPU which in turn sorts it (processes it) and sends it to the hard drive for storage. The hard drive will spin up and the arm will use its “˜write‘ heads to overwrite the previous image with the new one. Job done.

That is what that buzzing disc in your computer gets up to all day. Now, as I do with most of my articles here on MUO I shall leave you with a friendly word of advice:

If you want to look inside to further understand how does hard drive work, do so with an old one. There are a few reasons for this.

  • Once you pop open that drive, plugs on the screws will snap to tell the manufacturer you have been poking around in there. By doing this, your warranty is void immediately. Many drives actually have this warning printed on the side.
  • They’re expensive and carry a lot of important info so don’t just pop open the family PC to have a go at it. Pick up an old one on eBay.

tell us what YOU know about HDDs, share your thoughts 🙂

How to Stop Being an Oversensitive Employee and Work with a Boss You Hate


Sometimes we have the pleasure of working with a manager we really like and respect, and who respects us too. Other times, the relationship isn’t so great, and we have to deal with someone we can barely tolerate. Still, with the job market being what it is, you don’t want to just quit every time you work for someone you don’t get along with. Here’s how to grow a thicker skin at the office and learn to deal with a boss you may not want to see every morning.

Is Your Boss a Bad Person or Just a Bad Manager?

The first thing you need to figure out is whether your boss is a bad manager or a badperson. The former implies that he doesn’t give you the direction, priorities, and guidance you need to succeed at your job. The latter is a highly subjective way of saying the two of you don’t see eye-to-eye for personal reasons. If your boss is just a bad manager, you can functionally compensate for their issues with planning and structure. If your issue with your boss is one of personality, your job will require some perspective-checking on your part. Still, there are ways through both problems, but you’re not going to make any headway at all if you’re not clear on which issue you’re facing. Photo by Istvan Hajas (Shutterstock).

Find Out If You’re Part of the Problem

Here’s a question you probably don’t want to ask yourself: are you the problem here? Remember, everyone’s the hero of their own story, and everyone believes they’re the party in the right. Your manager is no different. Step back for a moment and ask yourself if you’re contributing to the poor relationship.

On Careers notes that many frustrated employees may just be oversensitive to the criticisms and natural flow of their workplace. For example, if you’re caught up in the tone or approach your boss uses to discuss things, you miss the message underneath. If you’re simply reacting to your boss instead of responding to the issues they bring up, you’re probably letting your emotional responses get the better of you.

We’ve discussed how to take criticism like a champ and without getting worked up over the tone or delivery. Focus on the message, and in this case the work, instead of your boss’s personality. Try to separate your emotional response from the things that irritate you, and give your boss clear but professional feedback when they do things that make you uncomfortable. You’re both adults, you can act like it. Choose your battles wisely, and understand that you both have to work together.

Differentiate “Like” and “Respect”

In the military, you don’t get to choose your boss. You don’t even get to just quit when you run up against someone you don’t really like working for. You have to adapt, adjust, and find a way to figure out your differences and move on. Granted, working in a corporate IT department or helping customers on the sales floor isn’t the same as being in the service, but you can take a few cues from our friends in uniform. Remember, you’re not at work to make friends. It can be great to make friends at work, and you should try if you can, but you need to separate whether you like your boss from whether you can learn to respect their position. Photo by Tom Wang (Shutterstock).

We’re not glossing over how difficult this can be. When About.com polled its readers asking what traits made someone a “bad boss,” most of them had common refrains: their boss didn’t respect them, or had never earned their respect. Their boss wasn’t qualified to do their jobs, much less manage them. Their boss was terrible at communicating, or setting expectations or priorities. These are all difficult to overcome, but getting past them starts with at least respecting the fact that they’re your manager. That doesn’t mean accepting everything they do, or even respecting them as a person, but it does mean accepting and understanding that you have to work with this person somehow. The rest is small stuff you can work through.

What You Can Do By Yourself to Cope

Even if your job sucks, that doesn’t mean you can’t fix it. Let’s start with ways you can manage yourself. Whether your issues with your boss are personal or professional, you can benefit from some simple coping mechanisms that will help you deal with a bad boss on your own. Photo by bottled_void.

  • Understand what stress does to you and how to fight it. If your boss stresses you out and makes you angry, you might benefit from simple office-friendly stress relief tricks like meditation, deep breathing for 10 seconds, or taking a walk to calm yourself before responding. If your boss is right in front of you and you’re getting angry, try to intercept your emotional response and let them know you’ll respond appropriately later. Whatever you do, separate the content of the message from its delivery. Focusing on the former is useful; focusing on the latter is a recipe for trouble.
  • Keep a work diary or a paper trail of interactions with them. If your boss is sexist, racist, or makes you uncomfortable at work, a work diary can be a great tool if you need to report them to someone higher up, but in this case we’d suggest using it as catharsis. Writing down how you feel and how your interactions with your boss makes you stressed out goes a long way towards helping you cope. You can keep your thoughts private, enjoy the benefits of getting it all out, and go back to work.
  • Find a mentor, or another manager you can look up to. A mentor, even a manager in another department, can often help you understand your boss’s pressures and challenges in a non-threatening way. They may be willing to level with you in a way your boss isn’t. Plus, while you may not be able to tell them everything, the whole point of having a mentor is to help you learn, grow, and develop your skills—which include working with difficult people. Photo by Huntstock (Shutterstock).
  • Draw bright lines between your work and your life. Get a hobby outside of work. Exercise. We discussed how bad bosses can follow you home, and some of the best coping mechanisms you can muster are the ones that force you to remember and enjoy what you’re working those long hours for in the first place. Spend time with family and loved ones, and make sure to fiercely protect your personal time away from work. Set your boundaries, and go to bat for them when you have to. Keep your relationship with your boss in its little box until you have to deal with it and enjoy living your life.

All of these coping mechanisms are things you can do for yourself to help improve your mindset. We’re not getting into the “It’s not fair that I have to learn to cope while my boss can continue being a jerk” battle. Like we said, we’re all adults here, and we’re all professionals. The moment you get stuck in that bean-counting, tit-for-tat mindset where “why should I have to do anything,” it’s over. We don’t always get to choose who we work with—sometimes you just have to suck it up and work with what’s in your power to change.

What You Can Do With Your Boss to Repair Your Relationship

Now that you have some tools to work on yourself, it’s time to work on your boss and peel back some of those layers that you hate. With luck, you’ll find something you can work with. Here are some suggestions to help.

  • Get closer to your boss. If your boss’s problem is that they don’t communicate, or set priorities or expectations for the work they assign you, get in good and close with them. Meet with them regularly—even offer to schedule the meetings yourself—to discuss those priorities and the things you’re working on. Yes, those meetings could result in even more work, but wouldn’t you rather get it every Wednesday at 3pm when you’re talking work anyway than on Friday at 4pm when it’s due before the end of the day? Plus, setting a time where you can talk about work gives you the opportunity to push back and ask your boss what can come off your plate to make room for the new stuff you have to do.
  • Learn to “manage up” and give constructive criticism without sounding like a jerk. Like we mentioned earlier, you and your boss are both adults and you’re both professionals. Unless your boss is both a bad manager and a bad person, they’ll understand a little constructive criticism from time to time, especially if you deliver it properly. Let them know what about their behavior and demeanor is getting under your skin. Come armed with suggestions that might improve your relationship too—telling them you hate when they talk to you isn’t helpful. Asking them to pull you aside to talk privately when they have a concern or asking them “What can I/we do to make this work better,” is helpful.
  • Work with your boss’s skills and on his/her priorities. The fact is that the most qualified people for a job don’t always get it. Sometimes a manager is brought in from another department because they’re owed a favor, or because the company couldn’t find someone to fill a role. Sometimes you’ll have an engineer leading a team of project managers, or vice versa. Get familiar with your boss’s background and see how you can relate on common ground. While you’re at it, find out what their priorities for your team are, and who your boss works hardest for. That should give you some insight on what you should be paying attention to and who’s projects are most important to your boss. A surefire way to take the heat off is to work on your boss’s priorities first.
  • Don’t just be an employee, be your boss’ assistant. Use your one-on-one time with your manager to discuss upcoming priorities as well. Don’t leave any excuse for you to not know what your boss is working on, or what rumors or rumblings your boss may be privy to that will have an effect on your workload. We’re big fans of the weekly review. Bring your boss in on it as well, or schedule one just for the two of you. If you have a small team, suggest to your boss that you all spend a short time each week clarifying priorities and talking about what’s on everyone’s shared plates. Doing so will get your boss communicating with you in a group setting, and take some of the sting out of their poor managerial skills. Photo by Riza Nugraha.
  • Solve problems and propose solutions as a way to get revenge. It’s often said thatliving well is the best revenge, so flip the problem on its head and kill your boss with kindness and productivity. If your boss makes you upset, treat them like a bully: Don’t give them the satisfaction of a reaction—instead give them exactly what they’re supposed to want in their role: a solution to the issue they’ve brought up. Solve your work problems, take credit for them, and then let them know the good work you’ve done (make sure to do it in that order so they can’t steal your thunder.) Take the initiative, and make yourself appear to be your boss’s peer to your colleagues and customers, not their subordinate. The best way to do this, of course, is to do great work. Let your bad boss transform you into a better employee.

If the problem with your boss is that they’re a bad manager, sometimes using personal leverage and common ground to get around their managerial problems is the best way for you—and for them—to succeed. After all, part of working for someone is to help cover their butt—if you prove to your boss that you’re interested in doing this, they’ll be more willing to work with you. If the problem is personal, sometimes getting close enough so you grow on one another is the key to breaking the wall between you. Working on the same priorities towards a common goal can melt even the thickest ice. Remember, you’re on the same team here.

If All Else Fails, You Know What To Do

If nothing else works, quit. Sometimes all of the common ground, shared priorities, coping mechanisms, and de-stressing techniques can’t heal the rift between you and a bad boss. That said, don’t just quit at the first sign. It’s easy to say “your boss sucks, get out of there” when you’re good at being employed, or if you’re someone who’s already employed talking to someone who loves their job but hates their manager. Sometimes it’s worth it to try and work it out, and working it out takes effort and time. Give it a try first. Photo by Carey Ciuro.

If that doesn’t work though, it might be time to look for something else. If you love your company, see if you can find another opening in-house you can transfer to. Thatcomes with its own risks, but it may be worth doing to stay where you love the work. Otherwise, make a graceful exit. Granted, there’s no guarantee that you won’t wind up in a new job with a new boss you hate, so plan carefully and make sure to check yourself before doing anything rash. Worst case, maybe you’re just not cut out to work for someone else, and you should consider working for yourself or starting your own business. In both cases, you get to work for yourself, and if you boss still sucks after that, you have a real problem.

By ALAN HENRY lifehacker.com

5 Tech Myths: Cell Phones Don’t Cause Cancer & More


tech mythsMyths are more common than most people will admit. They perpetuate because they sound like they could be true – and nobody has time to fact-check every last detail. Eventually, as the myths are repeated time and time again, they sound more factual than the truth.

Technology is as susceptible to myths as any other niche. The complexity of the subject, combined with the rapid introduction of new, unfamiliar innovations, creates a perfect breeding ground for misunderstanding. Let’s set these tech myths straight.

RAM Usage Is Bad

tech myths

MakeUseOf will occasionally receive a question from a reader that asks about how to reduce RAM usage on a computer, tablet or smartphone. Their alarm is understandable. A user browsing the web in Windows 7 might open their task manager to find over six gigabytes ofRAM used. “Ack!” they think, “no wonder my computer is so slow!”

In truth, this relationship should be flipped on its head. RAM is very, very quick. Mechanical hard drives and some forms of flash storage (like most SD cards) are slow. By storing data that might be needed in RAM, a computer can increase the load speed of frequently accessed software. If RAM is not full of data, it’s effectively doing nothing, so why have it sit empty?

Smartphone users shouldn’t worry for the same reason. Background apps can negatively impact performance on an Android phone, but this usually isn’t because of memory. Instead, the culprit is usually an app that’s running in the background. Clearing memory appears to improve performance only because the offending app is closed to free up space.

Improperly Unmounting A USB Drive Will Delete Data

tech myths busted

Windows has long sounded the alarm about improperly unmounting disk drives. To this day, you may still receive warning messages when you remove a drive that you haven’t properly disabled through the operating system. Given the alarm, you’d think that the consequences of disobeying would be disastrous.

Not true. USB drives can be freely removed from a computer without issue in most situations. I can attest to this personally. As part of my work, I often have to move flash drives from one PC to the next, and I’ve never lost data from a drive because of it.

So why the warning? Microsoft is playing it safe. Data corruption can occur, but only if a USB drive is actively in use at the moment it is unplugged. Most users don’t do this. Still, Microsoft doesn’t want to be on the hook for the 1-in-1000th  time it does occur. And that’s why the alarm is raised even when there’s no fire.

You Don’t Need An Antivirus If You’re Careful

tech myths busted

Whenever I write an antivirus article I inevitably receive a reply from some smart-alec who claims that you don’t need an antivirus if you’re careful. Viruses come from infected files, right? So just don’t download them! You’ll be fine.

Well, actually, that tech myths couldn’t be more wrong. A decade and a half ago, most viruses were distributed through infected files, but they’ve become far more sophisticated since then. Worms, a specific class of virus, can infect any vulnerable computer through networking exploits. Other viruses spread using browser vulnerabilities. And still more are designed to spread via USB drives or local networks.

Clever users might respond by claiming people don’t have to worry if their software is up to date. This too is no guarantee. Zero-day exploits are common and even a patched system is a sitting duck. An antivirus may be able to stop such an attack (even though it’s unknown) by using heuristic detection to raise the alarm when a file behaves suspiciously. Those without antivirus, however, have no defense.

Cell Phones Cause Cancer

tech myths busted

Many consumer technologies rely on energy and therefor emit or use some form of radiation. Even radio waves are a form of radiation, and since cell phones use them, there’s been concern that having a source of radiation close to our heads could cause cancer. This has been backed up by an alarming report from the World Health Organization which labeled cell phones a “Class B Carcinogen”.

You’d expect that to be based on some fairly hefty evidence, right? Actually, the WHO report is less damning than it sounds in headlines. Class B simply means that a study has indicated that there might be a link, but the link is too weak to be definitive. Meanwhile, numerous other studies have found no link. This includes a massive Danish study involving 350,000 people that was released in late 2011.

Further evidence against the risk of cancer can be found in what we know of physics. Radiation comes in multiple forms, and humans only need to worry about radiation energetic enough to damage DNA. Ultraviolet rays from the sun, which can cause skin cancer, are over 400,000 times more energetic than those emitted from cell phones. Low energy waves like radio can’t hurt DNA, and that means they can’t cause cancer.

Everything Electronic Causes Cancer

tech myths

This means that what holds true for cell phones should hold true for other wireless devices, as well. The rise of wireless networks has caused distress about what all those waves bouncing through the atmosphere might do to our cells. The answer is simple – nothing.  Sleeping on a bed made of wireless routers would be uncomfortable, but it’s not going cause cancer.

Some users become concerned because of another alarming effect. Heat. As electronics are used, they put out heat, and that heat is absorbed by our bodies. That’s why your thighs are warm after using a laptop.

Computers can be harmful if they’re too hot, but the problem isn’t limited to electronics. Dermatologists have long known that constant exposure to heat can cause scaly, discolored skin which is often permanent. A hot computer can cause this – as can a heating blanket, seat warmer, fireplace or oven.

While skin discoloration and minor burns can be a problem to a handful of people, there’s no evidence that normal, intermediate use of a computer will cause cancer. The lesson from dermatology is simple. If something is hot, don’t hang around it too long.

Conclusion

This is merely a handful of tech myths. There are plenty more out there, ranging from the believable to the utterly outrageous. Have you heard a tech myth that you later found out wasn’t true? Tell us about it in the comments.

 

By Matt Smith makeuseof.com

What’s A Cookie & What Does It Have To Do With My Privacy?


Most people know that there are cookies scattered all over the Internet, ready and willing to be eaten up by whoever can find them first. Wait, what? That can’t be right. Yes, there are cookies on the Internet (technically, the World Wide Web), and yes, they really are called “cookies”.  But they aren’t delicious and they can affect your privacy, so you should know what they do.

Whether you’re browsing Google search results, logging into Facebook, or just innocently chatting away on an online forum, you’ve encountered cookies. They aren’t inherently harmful but, just like passwords or email addresses, they can be exploited when placed in the wrong hands. Keep reading to learn how you can protect yourself.

What Are Cookies, Really?

In simple terms, cookies are just files that reside on your computer. Cookies are created when you visit a website. They are used to store bits of information about your interactions with the website, which the web server can use later when processing your sessions. The cookie is specific to you and it can be read by the web server (when interacting with it) or by programs on your computer.

To be technical, your browser is the program that mediates cookie control between your computer and the website. These cookies used by a website to present different types of content depending on who you are in relation to that website. Cookies can expire after a given time period (usually determined by the website issuing the cookie), but if necessary, they can be manually deleted.

Why are cookies used? Because they’re convenient and efficient. If a website wants to service thousands of users without cookies, it would have to store all of that interaction data in its own storage and it would have to be processed on its own. By offloading that work to the user, it becomes a faster and less strenuous procedure.

What are cookies used for? One reason for a cookie is to identify you. If you log in to a website and close your browser, then open it back up, the website knows it’s you because that cookie exists (it was created when you logged in). Cookies can store all sorts of information, like your preferences, your browser type, your location, etc. and this information can be used to better your experience.

How Do Cookies Affect You?

For the most part, cookies are NOT harmful. They’re just another protocol used on the Internet to facilitate communication between users and servers. Worried about viruses and malware? You can relax. Cookies cannot carry viruses or malware, nor can they transfer such things to other users.

Cookies are a necessary part of the Internet experience and they shouldn’t be feared. For example, deleting your cookies will log you out of sites like MakeUseOf and Facebook. If you like convenience and personalization, then you should learn to embrace cookies.

But what should you worry about?

The worst possible scenario would be the interception or forgery of one of your cookies, which would allow another user to impersonate you on some website. This could result in them eavesdropping on your user data OR hijacking your account credentials. However, don’t be too alarmed. Cookie security mostly depends on the website and your browser; a cookie encryption feature, for example, can help protect you from hackers.

A more prevalent issue is a specific type of cookie called the “tracking cookie.” These cookies aren’t used to better your experience. Instead, they keep track of all of your actions on certain websites. These can be used to build browsing history profiles, which can be used to target specific ads to you. This is where invasion of privacy comes in.

Protecting Your Privacy

Here’s what you need to know about cookie privacy: they cannot know any information that you don’t personally provide. In other words, just because a website has a cookie on you doesn’t mean that they know everyone in your family and which schools you’ve attended–unless you entered that information to the website.

The biggest problem with tracking cookies is that an advertising agency can view your browsing history (since that’s what they use to target ads relevant to your interests). You can prevent them from doing this, of course, by playing with your browser settings and disabling cookies.

If you don’t want to disable ALL cookies (which would keep you from enjoying the legitimate features on legitimate websites), certain browsers let you disable specific cookies from certain domains. Some more advanced browsers let you synchronize with black lists; these are maintained by people or communities to keep out domains with shady cookie practices.

Ultimately, when it comes to cookie privacy, it’s all about trust. Do you trust that website to log every interaction? Read their privacy policy and terms of use–they’re usually linked on the website near the header or footer. If you don’t trust them, you can always wipe your cookies later.

Want to test a website’s cookie integrity? Try “Cookie Checker”. Want to see what sort of cookies are on your computer and what websites are tracking with those cookies? Try Cookie Spy.

By Joel Lee makeuseof.com

How Does File Compression Work?


We’ve all heard of file compression. Anyone who regularly downloads files from the web is familiar with formats like ZIP and RAR, and anyone who edits media files knows that compression is necessary to share images, music and videos on the web without using up all of your bandwidth. File compression is at the core of how the web works, you might argue, because it allows us to share files that would otherwise take too long to transfer. But how does it work?

It’s nothing magical, but it is the result of a lot of hard work by many very smart people. Let’s explore how file compression works by looking over the two main types of compression – lossless and lossy.

Just a warning – I’m going to oversimplify things here in an attempt to make this readable by non-math majors. Check out the linked-to Wikipedia articles for more depth, and Wikipedia’s sources for even more.

Lossless Compression

Lossless compression basically works by removing redundancy. What does that mean? Let’s simplify things. This stack of bricks will represent our data:

how does file compression work

As you can see we’ve got two red bricks, five yellow and three blue. The simplest way to represent this is as you see above: the bricks themselves. But it’s not the only way I can represent this. I could also do this:

how file compression works

In the above image you can see the exact same information – two red, five yellow and three blue – but it takes up significantly less space. I’ve represented redundant bricks using numbers, meaning I need only three bricks to represent ten.

This gives you a rough idea how lossless compression is possible. Information that’s redundant is replaced with instructions telling the computer how much identical data repeats. Another simplified example:

fffffffuuuuuuuuuuuu

Can be “compressed” to:

f7u12

This is only one method of lossless compression, of course, but it points to how this is possible. Other math tricks are used, but the main thing to remember about lossless compression is that while space is temporarily saved, it is possible to reconstruct the original file entirely from the compressed one. If you see three bricks with numbers you know exactly how to make the stack. No information is lost, just as the name lossless implies.

Programs like WinZip are based on lossless compression. They remove this redundant information when you compress (or “zip”) the file and restore it when you uncompress (or “unzip”). Nothing is lost.

In the image world, PNG files also use lossless compression. This is why they offer a smaller file size for images with lots of uniform space: that redundant information is represented using instructions.

Of course, this is all an oversimplification, but it gets the basic point across. Read more about lossless compression on Wikipedia, if you’re interested.

Lossy Compression

Of course, there’s only so much you can accomplish using only lossless methods. Happily they’re not the only option: you can also simply remove information. This is called lossy compression, and it’s not as crazy as it sounds; in fact, you probably have many files on your computer made using lossy compression.

An MP3, for example. If you’re like most people your computer stores thousands of them for you, but did you know they don’t contain all of the audio information the original recording did? Some sounds, which humans cannot or can barely hear, are removed as part of the compression. The more you compress a file the more information is removed, which is why an overly compressed file will start to sound muddy.

Lossy compression tends to mostly be used for media files – pictures, sound and video. Using lossy compression for a text file would be problematic, as the resulting information would be garbled. It’s not always necessary for media files to include all the information, however.

Another example of lossy compression is the JPEG image. Generally speaking images seen on the web do not need to be as high-quality as images intended for printing. As such, you can remove a lot of redundant information in a web image, even if doing so would look awful printed.

Of course, repeatedly compressing a file using lossless methods decreases the quality – every time you do it more data is lost. Below is a photo I’ve compressed three times to demonstrate this:

how does file compression work

You can see from left to right how the quality decreases. It may not matter, depending on what the image will be used for, and that’s why lossy compression exists.

It’s important to remember that files compressed using lossy methods actually lose data, meaning you cannot recreate the original file from one compressed using lossy methods. It’s obvious when you think about it, but many printing projects have been ruined for lack of understanding this key point.

I’ve really only scratched the surface here, so please: read more about lossy compression on Wikipedia. It’s kind of fascinating.

Conclusion

Compression helped make the web what it is. In the days of dialup compressed images brought photos to our browser, at least not at an acceptable speed. Compressed video makes sites like YouTube possible, and anyone who uses file sharing networks is familiar with ZIP and RAR files.

Do you have anything to add? I’m sure I’ve missed some key points so educate me (and the other readers) in the comments below.

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