Upload and Download

As you know by now, the Internet allows files to be exchanged between computers.  When you are just viewing webpages, the contents of the page are only temporarily saved on your computer (just for as long as you are viewing the page).  Web browsers can only read certain file types, namely those with the .html extension (HTML files) and certain picture files like .jpg, .gif, and a few others.  There are other file types that you might encounter on the Internet that you want to see, though, such as Word files, music files, etc. that the browser cannot open.  In order to open them, you need to transfer a copy of the file from the Internet to your computer, and open it with an application on your computer.  The process by which files are transfered from the Internet to a computer is called downloading.  Once a file is downloaded, it can be treated just like any other file you created yourself on your computer.  Two of the most common sources for downloads are emails and the iTunes music store.  Downloading is an amazing process—I can write a novel on my computer and send it (attached to an email) anywhere in the world and the email's recipient could be reading it within seconds.  With great power, though, comes great responsibility: while many downloads are regular, harmless files, there are a large number of files that contain viruses and other programs that can harm your computer or steal your information.  These files are often disguised as regular files, so it is important to use caution when you click on a link to download a file.  Only click on links that appear on web sites that you trust!!!  A good rule of thumb is that if you don't expect to have to download a file, don't download any files.  Also, only download attachments from emails if you know the person who sent the email to you.  Many email services have great software that tries to filter out messages that have viruses attached to them, but none of them is perfect, so it's always best to err on the side of caution.

A much less hazardous process than downloading is the reverse: uploading.  When you want to share a file with someone (or the whole Internet), you need to upload it to an email or web site so that others can download it to their computers.

Examples

When you buy a song from iTunes, you have to download it in order to play it on your computer.

A file that contains a virus may appear as simple as this (this is not a real virus, or even a real link):

Congratulations! You just won $100!!!!! click here to claim your prize.

Even though you might be flattered at the thought of winning $100, since you did not log on to the Internet today to claim a lottery prize, you are better off not clicking the link.

Most email programs have a button that says "Attach a file" or has a picture of a paper clip on it.  Clicking that will let you choose which file you want to attach, and when you send the message, your file will be uploaded to the Internet.

Up Next: Navigating through your computer

Earlier Topics Revisited

Now that you are more familiar with some of the terminology and functions related to computers, let's go back and elaborate on some earlier topics:

• Bits and bytes: these are the building blocks of software, such as programs, applications, and operating systems.
• Interface, input, and output: things like keyboards, mouses, and computer screens are interfaces.  So are operating systems (connect hardware to software) and (new term) GUIs (Graphical User Interfaces), which translate text commands into pictures.  GUIs are responsible for clickable buttons, file icons, and menus.
• Keyboard: by now, you know how to type capital and lowercase letters, numbers, symbols, and accents using keyboard modifier keys.
• Program and application: you know about programs such as web browsers (Internet Explorer, Firefox, Safari) and word processors (Microsoft Word).  You also know that programs are contained in windows, and you know how to close, minimize, and maximize windows.
• The Internet: connects computers so they can exchange files.  The most common way to access the Internet is through a web browser, where you can see files (web sites) residing on other computers.
• Menus: the File menu has options for opening new files and saving or closing current ones, while the Edit menu has options for editing the text or some other aspect inside of the current file.
• Media: different kinds of files that are usually meant for entertainment (consider the term "the media industry"), commonly video, picture, and music files.
• Files and Extensions: different kinds of files are represented by different endings to their names: .doc, .txt, .jpg, .mp3, etc.

Hopefully this list connects some of the terms discussed earlier and provides a broader picture of the way computers work.

Next Up: Upload and Download

Files and Extensions

A file is a set of computer code (software) that contains all of the information necessary to complete a particular task.  There are different kinds (or types) of files, denoted by different extensions, which consist of a period followed by (usually) three letters that abbreviate the kind of the file.

Examples
Applications are files, and they are denoted by the .app extension on Mac OS X, and by the .exe extension on Windows (.exe stands for "executable file").  Other common files are Microsoft Word files, which contain whatever you wrote on Microsoft word.  These have the .doc and .docx extension (both stand for "document," but the x in .docx is to distinguish the newer version of Word from previous ones).  Here are some others:

• Microsoft Excel: .xls and .xlsx
• Microsoft PowerPoint: .ppt and .pptx
• MP3 and AAC (music files): .mp3 and .aac
• MPEG (video files): .m4p and .mp4
• Web Pages: .htm and .html
• Plain Text (i.e. without formatting like color, size, font): .txt
• JPEG, GIF, TIFF, RAW (images/pictures): .jpg, .gif, .tif, .raw
• PDF (Portable Document Format): .pdf

Tomorrow: Revisit some previous topics with our new tech-lingo

Operating System

An operating system is an application (piece of software) that acts as an interface between the computer's hardware and other applications on the computer.  It is also responsible for coordinating what happens when the computer turns on and off.  While it is possible to have two or more operating systems on a single computer, most computers only have one.


Examples
The two most popular operating systems are Microsoft Windows (XP, Vista, and 7)

 and 

Apple Mac OS X (Tiger, Leopard, and Snow Leopard).






A third operating system that is gaining popularity is called Linux, and it comes in widely varying varieties, called "distributions."  The most popular distribution is called Ubuntu (pronounced "oo-boon-two").  Ubuntu is the distribution most similar to Windows and Mac OS X, while other distributions are much more complicated to run, and are mainly used by computer programmers and other people who like to tinker with computers.


Tomorrow: The Internet!

Software

Software is the non-physical part of the computer that is encoded in bits and bytes, rather than hardware, which is the physical part.


Example
Programs and applications are pieces of software, since even though they are sold on CDs (for example), you don't buy it for the CD, you buy it for the information on the CD.


Tomorrow: Operating System