you download a file, you access
digital information (electronic “bits”)
from a remote computer using a modem. Almost
everything you do on the Web is some form of
downloading—it's as simple as clicking
your mouse. When you open a Web page, for instance,
you are actually downloading a file and its
associated graphics from a Web server.
Your Web browser then attempts to display the
Web page or file. First, the browser checks
the file extension for the
page (the letters following the period after
the file name, like "doc" or "htm").
If your browser is unable to recognize the
extension, you are prompted to select a viewer
for the file—that is, you tell the browser
which software program to use to view the file.
You also have an option to save the file to
your computer or to the network drive of your
You can also download files by clicking the
link to the file with your right mouse button
(or holding down the mouse button if you are
using a Macintosh) and then selecting Save
to Disk from the pop-up dialog box.
Depending on your browser configurations, you
are prompted to save the file to your hard
drive (C drive), or the file downloads automatically
to your computer desktop.
files from the Internet is a simple process
that usually requires few steps. Depending
on the file type, you can download files by
opening them, by choosing to save them and
then opening them, or by saving them and extracting
or decompressing them. Instructions and tips
for downloading files are included here.
Downloading and saving a file
To download a file, save it to your local computer
drive or network drive. Most Web browsers ask
you to choose a folder where you want to save
the file. Make a note of the name and location
of the folder so you can easily find the downloaded
Restrictions to downloading
Almost any file found on the Internet can be
downloaded and saved. Sometimes, however, you
can't download a file; there are many possible
size. The file may be too large
and too slow to download.
type. You don't have software needed
to view or use the file.
restrictions. Your organization
does not allow the file to be downloaded
because of its type, content, or source.
cost. The overwhelming majority
of files available on the Internet are either
free or available for a trial period at no
charge. Others must be paid for, and many
require you to electronically sign or accept
a licensing agreement that restricts use,
distribution, sharing, editing, or manipulation
of the file.
File types and extensions
for information on the files types most commonly
size and what it means
file size is measured by the number of electronic
signals or “bits” that make up
the file; 8 bits make up 1 byte. Typically,
file size is expressed as the number of bytes
in the file. Common units of measure for file
size are listed here.
- 8 bits
equal 1 byte—teeny
tiny, the smallest standard unit of measure
for digital data.
- 1,024 bytes
equal 1 kilobyte (KB)—still
- 1,024 kilobytes
(KB) equal 1 megabyte (MB
- 1,024 megabytes
equal 1 gigabyte (GB
You need lots of space for files this size.
- 1,024 gigabytes
equal 1 terabyte. Sounds
dinasaur size, and it is. You probably can't
download or store a file this size.
Note: To simplify size calculations
and comparisons, many people simply replace
1,024 with 1,000. The relative sizes are
not affected. Digital
data is already so compact that the size
difference between the two numbers (1,024
bytes and 1,000 bytes) and related measurements
is not significant.
computers can now store many very large files;
personal computer storage may be up to 1 GB.
Many businesses and organizations extend this
storage capacity with connections to a much
larger network storage system. However, file
size can have a significant impact on the time
required for downloading. While most Internet
files download within seconds, large documents
or pieces of software may take many hours to
download. You can find more information about
downloading in the section
Common problems with downloading.
types and extensions
Why do I
need to know the file type (or "format")?
you can identify the file type, you know what
the file contains (text, graphics, audio, a
program), whether the file will work on your
computer, and what software you need to decompress,
play, or view it. To determine the file type
or format, look at the file extension. The
file extension, typically 2 to 4 letters, follows
the file name and is separated from the name
by a period or dot. The file extension is an
abbreviation for the file type. For example,
a file called "Tryit.htm" is named
"Tryit" and has the extension "htm".
Common file types are described here.
file types (.htm, .html, .asp)
Files developed for the Internet use the extensions
.htm, .html, and .asp. HTM and HTML files are
Web pages; ASP files are Web pages that support
interaction with a user. ASP files don’t
work as stand-alone files. Their use depends
on their deployment by a server and their connection
to other files and software through the server;
ASP files work only because they reside on
the Internet. When you access HTM, HTML, and
ASP files, they automatically download to your
computer, are placed in a special Internet
“cache” folder, and can be viewed
through your browser. From your browser, you
can save and print these files.
file types (.doc, .txt, .rtf)
Text file types are usually word-processor
files; most users are familiar with these file
types. Text files use extensions like .doc
(for “document”), .txt (for “text”),
and .rtf (for “rich-text format”).
These files can be created using software like
WordPerfect, Microsoft Word, Notepad, or similar
programs. Text files sometimes contain objects
that are actually files themselves. Like software
programs and video and sound files, text files
can be compressed to speed up downloading.
You can save text files to your computer and
view, print, and edit them with the appropriate
also PDF types.
Graphic file types (.jpg, .gif)
The most common graphics file types on the
Web are those with the extensions .jpg and
.gif. JPG is short for JPEG (Joint Photographic
Experts Group), a popular compression standard
for photographs and other images. The .gif
extension stands for Graphics Interchange Format
(GIF). JPG files work well to compress digital
versions of photographs and naturalistic art,
while GIF files are used for logos, brushwork,
line drawings, cartoons, icons, etc. These
graphics file types are platform-independent
and can be used on a PC, Macintosh, or UNIX
platform as long as you have a viewer for them.
Video file types (.avi, .ram, .mpg,
.mov, .qt, .wmv)
Video files use several formats. Files with
extensions .avi and .ram run on PCs. The extension
.mpg (short for MPEG or Moving Picture Experts
Group) indicates a file type with a video standard
related to JPG. The MPG standard is platform-independent
but requires its own player; you need special
software to use MPG files. The extensions .mov
and .qt are used for QuickTime movie files.
QuickTime movies can play on a PC, Macintosh,
or UNIX platform. Windows Media Player can play a variety of video and audio file types. It comes standard on most Windows computers and can be downloaded for free. (exit site)
Sound file types (.mp3, .aiff, .au,
The most popular sound file type or format
is .mp3, which works for both Macintosh and
PC platforms. Other file sound files use the
extensions .aiff (for Macintosh); .au (for
Macintosh and UNIX); .wav (for PCs); and .ra
(Real Audio), a proprietary system for delivering
and playing streaming audio on the Web. RA
files can be played on any platform but require
proprietary software. Windows Media Player can play a variety of audio and video file types. It comes standard on most Windows computers and can be downloaded for free. (exit site)
Software file types (.exe)
Software files use the extension .exe for "executable"—these
files are not just for viewing, they do something
(execute actions). Most software files are
relatively large and are available on the Internet
in a special, reduced size format. These files
are “compressed” and use a file
extension .zip; these files
are described in the section Compressed
and self-extracting files.
you attempt to open an EXE file, you are prompted
to save or download the file. Save
to disk is the usual default option.
To save the file, simply click "OK"
on the dialog box. A second option, Open
from current location, is also available but
is usually not recommended. If you open an
executable file from the Internet or from e-mail,
you may infect your computer with a virus.
When the file is completely downloaded, open
the folder you chose for downloading. Double-click
the downloaded file. One of two things will
installation program opens and guides you
through the process of installing the software
No installation is required, and the program
For more information on file extensions and
how to interpret them, read the Learn
the Net (www.learnthenet.com)
article about file formats and extensions.
Check the index for this and other articles
about the Internet.
and self-extracting files
file types (.zip, .sit, .tar)
Some files that you download are extremely
large and are available only in a "compressed"
format. A compressed file is made up of a large
file or group of files that have been compacted
into a single smaller file. Files are compressed
by removing filler code. The reduced size of
compressed files saves download time and disk
The most common compressed files are those
with extensions like .zip (PC), .sit (Macintosh),
and .tar (UNIX). Files with these extensions
are commonly referred to as “zipped”
files. You need special decompression software
to decompress or extract these files, and each
compressed file type has its own decompression
software or utility. Decompression software
packages such as WinZip (www.winzip.com)
or Stuffit Expander (www.stuffit.com/expander/)
are available on the Internet. On this page,
compressed files for details on
ZIP files are very common on the Internet,
so we suggest you get a ZIP utility if you
do not have one. How do you know if you have
one? Simply download a zipped file and try
to open it after the download process is complete.
If the file opens, you have a decompression
utility. If you see an error message, you need
decompression software. If you don't have decompression
software installed, or if you aren't sure that
you do, download and install one of the decompression
programs mentioned here or a similar program.
Self-extracting file types (.sea, .exe)
Self-extracting files are compressed files
that run automatically after you double-click
the link to the file. Files with the extensions
.sea (Macintosh) or .exe (DOS/Windows) are
self-extracting and do not require a separate
software program to decompress and run.
For additional help, see the next section,
Extracting (expanding) compressed files,
with step-by-step instructions for decompressing
like WinZip and Stuffit Expander are used to
expand compressed, encoded files so that you
can view or use the files. These tools usually
work seamlessly with your Web browser and require
little maintenance. Check the tips and instructions
for working with common decompression tools
included in this section.
To decompress a file using WinZip (Windows
After a ZIP file has been downloaded and saved
to your local drive, the next step is to extract,
or decompress, its contents. Compressed files
contain one or more files or folders. Follow
these steps to extract a file.
the ZIP file that you previously downloaded;
WinZip opens automatically. The contents
of the ZIP file are displayed in the
WinZip interface, which appears as
a window on your desktop (see screen
capture). Note that the folder path
for each item in the compressed file
is shown on the far right. At this
point, the files are said to be in
the drop-down File
menu shown on the WinZip interface
(shown in Step 1), choose Actions
and then Extract to open
the Extract dialog
the All files and
Use folder names options,
as shown above. This ensures that all
files in the archive are extracted
and that the folder locations for all
files are re-created on your local
system or drive.
the Folders/drives window,
choose a folder where the compressed
files will be extracted, or click New
Folder to make a new folder
for the files.
TIP: Create a Download
folder on your hard drive, download any
compressed files into this empty folder,
and decompress the files into the same
folder. A Download folder allows you
to keep track of the files that come
out of the compressed file. You never
know how many files might be contained
in a compressed file. You can move the
files to the location of your choice
after downloading and extracting them.
Extract. The file is extracted
to the folder chosen.
problems with downloading
network traffic slows things down.
Sometimes so many people are connected to the
Internet that data lines become congested,
like a traffic jam at rush hour. Under these
circumstances a file being downloaded can "hang"
for an indeterminate amount of time. Sometimes
the download is “aborted”, which
results in an incomplete download—you
don’t have the complete file or set of
download server is busy.
Even when general network traffic is light,
a Web server can become overloaded with connections.
The maximum number of allowable connections
may have been reached; the server is at capacity
and can't handle more. In this case, you might
receive a message from your Web browser like
"Connection by server refused." This
rarely happens with servers for the NIP web
site because a large number of servers are
available, but it does occur.
You don't remember where you saved the downloaded
When you attempt to download a file from the
Internet, your browser displays a Save
As dialog box that prompts you to
choose where you want to save the file. Before
you click the Save button
in the dialog box, write down both the name
of the file and the folder where it’s
being saved. Files downloaded from the Internet
may have names don’t mean much to you,
but you can use the Save As
dialog box to rename the file so that you easily
remember the name. Tip: If
you know the file name but still can't find
the file after you have saved it, use your
computer's Find command to
search for the file on your computer.
Your computer has limited capacity.
files are downloaded, they are held in a "buffer"
in computer storage. If the buffer is small,
or if your computer's processor is slow, large
files can overwhelm the download capacity;
this happens most frequently with older personal
computers. Older modems often operate at low
connection rates (less than 56 kilobits per
second), and downloading even compressed files
can be slow and difficult. Small or slow capacity
means that downloading can be prolonged, taking
hours, or your computer may "freeze"
or "crash", and the download fails.
You can try downloading again or investigate
the limits of your computer and see if you
need to upgrade memory, storage, or processing
problems. If you experience problems
opening or keeping your connection to the Internet,
try one of these solutions.
from and reconnect to the Internet.
Disconnect from the Internet, restart your
computer, and reconnect to the Internet.
Connect again at a later time. Your Internet
Service Provider (ISP) may be busy and unable
to support more connections.
Call your Internet Service Provider or your
and using PDF files
the code used to create web pages, cannot support
all the formatting and presentation options
for many documents. In such cases, documents
are displayed as PDFs or Portable Document
Format documents; they are like snapshots
or pictures of the original documents. The
PDF format maintains the look and layout of
the original document.
easy to download, view, and print PDF files,
but it is not easy to change or edit them.
PDF files can be viewed across multiple platforms
(MAC, PC, UNIX) using the appropriate reader
for that platform. To ensure access to all
available PDF files, make sure the most current
Adobe viewing software, called "Adobe
Acrobat Reader," is installed on your
computer to display, print, and navigate any
PDF files. Older versions of
the reader will not reliably open PDFs made
with newer versions of the Adobe software,
so it is important to be sure you have the
current version. The Adobe Acrobat
software is available for downloading at no
cost from Adobe's Web site at http://www.adobe.com/products/acrobat/readstep.html
download a PDF file, click the link for the
dialog box from your browser appears asking
if you want to save the file. Specify where
to save the file.
Tip: On this web site, the
file size is sometimes listed next to the
icon for the file. File size suggests how
long a file might take to download. The speed
of your modem, the speed of your computer
processor, the size of RAM on your computer,
the volume of Internet traffic, and the resources
of your Internet provider all affect download
the PDF file has been downloaded, you can
view, navigate, or print the file using Adobe
Tip: To view or use PDF
files, a copy of Acrobat Reader® or Exchange®
is required. Adobe Reader® software is
available for no charge in various languages
and in versions compatible with several operating
systems, including Windows 3.1 and 95, Macintosh,
and UNIX. Documentation for installation
and operating requirements for Acrobat®
is included with the software.
the Acrobat software is installed, view PDF
files by opening them in Acrobat Reader®.
Acrobat Reader® toolbar to browse, view,
or print the entire document or any selected
pages within the document.
documents are easy to print. Click File>Print
on the Acrobat Reader®
Window toolbar to open the print dialogue box.
You can print the whole document or selected
pages within the document.
with Acrobat Reader: Please
check the information provided with Acrobat
or the Adobe®
website for any problems or questions about
using Adobe products.
If you are experiencing
difficulty opening Acrobat files, this is oftentimes
a conflict with the web browser integration
(allows .pdf files to open in the browser instead
of their own window). It is recommended that
you disable this feature for optimal performance
of this application. To do so, open the Adobe
from your start menu (or Desktop), under the
Edit menu, choose Preferences, then Internet,
and make sure the "Display PDF in Browser"
option is not checked. For
further assistance, refer to this help
on the Adobe®
3.x features a "PDFViewer" plug-in
compatible with both Netscape Navigator 3.x
and above and Internet Explorer 3.x and above
that allows for PDF viewing in your web browser
window. See the Online guide under
the help menu in Acrobat Reader®
for more information.
Use of registered trademarks and commercial
sources is for identification only and does
not imply endorsement by the National Immunization
Program or the Centers for Disease Control
Adobe, Acrobat, and Adobe Type Manager are
trademarks of Adobe Systems Incorporated and
may be registered in certain jurisdictions.
© Copyright 1994 Adobe Systems Incorporated.
All rights reserved.
The links on this page are provided to help
you find tools and information you may need
to use materials on the NIP Web site. These
links do not represent an endorsement of the
products or any commercial enterprise.